Journal of Athletic Training
2017;52(9):877–895
doi: 10.4085/1062-6050-52.9.02
Ó by the National Athletic Trainers’ Association, Inc
www.natajournals.org

position statement

National Athletic Trainers’
Association Position Statement:
Fluid Replacement for the
Physically Active
Brendon P. McDermott, PhD, ATC, FACSM*;
Scott A. Anderson, ATC†; Lawrence E.
Armstrong, PhD, FACSM‡; Douglas J. Casa,
PhD, ATC, FNATA, FACSM‡; Samuel N.
Cheuvront, PhD, RD, FACSM§; Larry Cooper,
MS, ATC¶; W. Larry Kenney, PhD, FACSM#;
Francis G. O’Connor, MD, MPH, FACSMjj;
William O. Roberts, MD, MS, FACSM***University of Arkansas, Fayetteville; †University of Oklahoma,
Norman; ‡University of Connecticut, Storrs; §US Army ResearchInstitute of Environmental Medicine, Natick, MA; ¶Trafford HighSchool, Harrison City, PA; #Pennsylvania State University, University
Park; jjUniformed Services University of Health Sciences, Bethesda,
MD; **University of Minnesota Medical School, Minneapolis
Objective: To present evidence-based recommendations
that promote optimized fluid-maintenance practices for physically active individuals.
Background: Both a lack of adequate fluid replacement(hypohydration) and excessive intake (hyperhydration) can
compromise athletic performance and increase health risks.
Athletes need access to water to prevent hypohydration duringphysical activity but must be aware of the risks of overdrinking
and hyponatremia. Drinking behavior can be modified byeducation, accessibility, experience, and palatability. This
statement updates practical recommendations regarding fluidreplacement strategies for physically active individuals.

Recommendations: Educate physically active people regarding the benefits of fluid replacement to promote performance and safety and the potential risks of both hypohydrationand hyperhydration on health and physical performance.
Quantify sweat rates for physically active individuals during
exercise in various environments. Work with individuals todevelop fluid-replacement practices that promote sufficient but
not excessive hydration before, during, and after physicalactivity.
Key Words: athletic performance, dehydration, hydration
protocol, hydration status, hyponatremia, oral rehydration
solution, rehydration, overhydration, fluid overloadI

youth sports19,20 arrive at workouts hypohydrated. When
access to ﬂuids based on thirst and voluntary ﬂuid intake isadequate during activity, humans replace roughly twothirds of sweat losses.2125
Maintaining hydration status with minimal variation(þ1% to –1%) allows the body to optimally thermoregulate5,26,27 and maintain cardiovascular function.7,28,29 Evaporative heat loss is the most effective mode of heatdissipation in warm or hot conditions. If the eccrine
sweating mechanism is compromised due to a lack ofavailable body ﬂuid, core temperature increases above that
expected for the activity and environment.30,31 Appropriate
hydration is similarly important for physical activity atn humans, total body water and overall hydration arenormally maintained within a relatively narrow range(1% hyperhydration to 3% hypohydration).1,2 The
beneﬁts of optimal hydration status include maintaining
athletic performance,36 maximizing the transfer of metabolic heat,5,7 maintaining mood,8,9 and facilitating recovery
from exercise.10,11 All may be compromised at modest
levels of hypohydration (approximately 2%).5,9 However,extreme deviations on either end of the physiological range(hypohydration or hyperhydration) can compromise healthand organ function.1214
A majority (more than 50%) of athletes in professional
sports,15 collegiate athletics,16,17 and high school18 and

Journal of Athletic Training877

altitude, for individuals with chronic disease, and forthermoregulation in cold environments.32,33
Conversely, excessive ﬂuid consumption can lead to lifethreatening exercise-associated hyponatremia (EAH), in
which extracellular body water enters the cells and causesorgan and tissue swelling.34,35 Although EAH is uncommon
in team-sport athletes, it has been identiﬁed in 10% to 20%
of distance athletes after events.35–38 The condition can befatal when brain cells swell and brain tissue herniates
through the foramen magnum or the brain swelling triggers
noncardiogenic pulmonary edema that leads to respiratory
failure.34 It is imperative that individuals remain within or
close to the normal range of plasma volume and serum
osmolality to prevent substantially low or high body water
volumes before, during, and after physical activity and tomaintain performance and health.
This position paper is an update to the previous National
Athletic Trainers’ Association (NATA) position statement
on ﬂuid replacement for athletes (published in 2000). It
expands the scope of recommendations and updates the
topic of ﬂuid replacement based on recent literature
regarding hydration in physically active individuals.
PURPOSESThis position statement is based on an extensive literature
review and includes deﬁnitions of normal and abnormal
hydration and ﬂuid-balance recommendations to help
athletic trainers (ATs) and other health care providers
1. Understand that ﬂuid losses and needs are variable and thatﬂuid-balance needs must be individualized for best results.
2. Educate physically active individuals on how to maintaintheir hydration status in order to avoid moderate to severe
hypohydration and EAH and promote safety and performance.
3. Know the importance of approximating or maintaining
euhydration before, during, and after exercise in physically
active individuals.
4. Develop hydration strategies to follow before, during, andafter physical activity.
5. Recognize the signs and symptoms of hypohydration and
EAH to enable differentiation of hydration concerns fromexertional heat illness and also understand diagnostic
procedures and point-of-care blood analysis.
6. Acknowledge when on-site treatment is appropriate forhypohydrated or hyponatremic patients and when totransfer for evaluation and management at an advanced
medical facility.
7. Identify unique personal characteristics (eg, age, diseasestates) and environmental variances (eg, altitude, cold) that
may alter the regulation of ﬂuid balance during exercise.

Hyperhydration

Hyperhydration is the state of excessive total body watercontent with expanded intracellular and extracellular ﬂuid
volumes. The body normally excretes the excess ﬂuids.
Exercise-Associated Hyponatremia

A potentially fatal condition, EAH is deﬁned as a serum
sodium concentration of less than 135 mmolL–1 during orwithin 24 hours of physical activity.13,3436 Exerciseassociated hyponatremia is a potential medical emergency
that is typically symptomatic at levels below 130 mmolL–1.
Dehydration

The process of losing body water is known as
dehydration. During exercise, body water is most often
lost through sweating. Water loss through urine (eg,diuretic use), respiration, feces (especially with diarrhea),or vomiting can also dehydrate the body.
Hypohydration

Hypohydration is a deﬁcit of body water that is caused byacute or chronic dehydration. Hypohydration represents acontinuum from both a clinical perspective (mild ¼ 1% to
5%, moderate ¼ 5% to 10%, and severe ¼ .10% body massdeﬁcit) and an athletic perspective (mild to moderate ¼ 2%
to 5% and severe ¼ .5% body mass deﬁcit) where mass ¼
volume. In athletes, a deﬁcit greater than 5% is consistently
associated with impaired performance, extreme thirst,
headache, and other symptoms; such a ﬂuid deﬁcit is
difﬁcult to replace, even with extended recovery time.
Drinking ad libitum

Derived from the Latin, drinking ad libitum (ad lib)means ‘‘drinking at one’s pleasure.’’ This consists ofconsuming ﬂuids when desired and of the selected or
preferred concentration, ﬂavor, consistency, temperature,etc. However, this strategy does not necessarily include theongoing assessment of thirst.21
Drinking to Thirst

Consuming ﬂuids as thirst dictates is called drinking tothirst. Thirst is the psychological sensation of andmotivation for seeking ﬂuids to consume. This strategy
involves consuming ﬂuids when thirsty and drinking
enough to limit the sensation of thirst before and throughout
activity.
EVIDENCE CLASSIFICATION
Strength of Recommendation Taxonomy

DEFINITIONS
Euhydration

Euhydration is the state of optimal total body watercontent as regulated by the brain. Intracellular andextracellular ﬂuid volumes are maintained with minimal
physiological adjustment. The body’s systems function
most efﬁciently in this state.
878

Volume 52  Number 9  September 2017

The recommendations in this statement are supported
using the Strength of Recommendation Taxonomy (SORT)
system.37 The letter indicates the consistency and evidencebased strength of the recommendation (A reﬂects thestrongest evidence base). For the practicing clinician, any
recommendation with an A grade warrants attention andshould be inherent to clinical practice. Less researchsupports recommendations with grades B and C; theseshould be discussed by the sports medicine staff. Grade B

Table 1. Signs and Symptoms of Hypohydration andHyponatremia
Hypohydration (Decreased
Total Body Water)ThirstFlushed skin
ApathyaDizziness or lightheadednessa
Nausea, diarrhea, or vomitinga
Heat sensations or chills
Headachea
Dyspnea (only in severe cases)a
Gastrointestinal cramping
General discomfort
Acute body weight lossaHyponatremia (Low Blood
Sodium Concentration)
Altered mental status
Muscular twitching or weakness
ApathyaDizziness or lightheadednessa
Nausea or vomitinga
Acting ‘‘out of sorts’’
Headache (progressive andsevere)a
Dyspneaa
Swelling of hands, feet, or both
Mood changes
Disorientation or confusion
Grand mal seizure or coma
Acute weight gain

Signs or symptoms that are common in both conditions,necessitating blood-sodium assessment for differentiation before
treatment. Note: A patient can be hypohydrated and hyponatremicat the same time.35,36,38,50

recommendations are based on inconsistent or limited
controlled research outcomes. Grade C recommendations
should be considered as expert guidance despite limited
research support.37
RECOMMENDATIONS
Importance of Maintaining Fluid Balance andRegulation
1. Among individuals in free-living conditions, habitualﬂuid intake and urine production are highly variable.1,20,3941 Furthermore, sweat rate,18,4244 thirst,21,4549
and ﬂuid intake19,20,24,43,5055 during exercise vary greatly.
Therefore, individualized ﬂuid-maintenance recommendations need to be considered for physically active
people. Strength of Recommendation (SOR): A
Importance of Maintaining Euhydration
2. Both severe clinical hypohydration and hyperhydration
can degrade athletic performance and are potentiallyfatal.3436,38,50,56–58 Early signs and symptoms of these
conditions may overlap, includinga. Thirst
b. General malaisec. Fatigue
d. Headachee. Vomiting

Later signs and symptoms of hypohydration (eg, thirst,
gastrointestinal cramping, heat sensations or chills) andhyperhydration (eg, extremity swelling, altered mentation,
mood changes, seizure) begin to distinguish the 2conditions, but prompt blood analysis (via point-of-care
devices if available) and measurement of body weight can
expedite accurate diagnosis (Table 1).35,36,38,50,58,59 SOR: B
3. Hypohydration leads to increased cardiovascular stressduring exercise.7,28,60 Health care professionals should
understand this fact, educate physically active individuals

appropriately, and apply strategies to prevent moderate tosevere hypohydration. SOR: A
4. Thermoregulation is compromised by hypohydration
greater than 1%,4 and the risk of exertional heat illness
increases at moderate to severe levels (greater than3%).5,27,29,6164 This is 1 of myriad factors known tocontribute to heat illness.65 Optimal hydration is a
modiﬁable factor that should be attempted to help preventthe onset of heat illness. SOR: B
5. Exercise-associated hyponatremia is caused by excessive
consumption of hypotonic ﬂuids (including sports drinks),
often combined with reduced renal water clearance,
resulting in maintained or increased body weight during
exercise lasting 1 hour or more. Physically active
individuals should not consume ﬂuid that exceeds their
exercise-related body mass losses and should monitor
their weight before and after exercise to conﬁrm
adherence.13,34,36,66 SOR: A
6. Individuals should not gain body mass (or body weight)
during exercise (from pre-exercise to postexercise) unlessthey begin activity with an unavoidable ﬂuid deﬁcit.13,3436,58,67,68 Hyperhydration confers no physiologicalor performance advantages and is not recommended,
except in speciﬁc situations with medical oversight andwhen factors necessitating hyperhydration before activity(eg, lack of ﬂuid availability during the event, known
excessive sweat losses) are present. Furthermore, if
hyperhydration reduces blood sodium concentrations, it
can lead to EAH. SOR: A
7. Euhydration (þ1 to –1% compared with baseline values)
aids thermoregulatory control5,7,27,28,30,60–63,6971 and helps
prevent symptoms of heat illness.63,72 Athletic trainers
should promote euhydration in this range before exercise
and a body mass loss of less than 2% at the end of
exercise. SOR: A
8. Physically active individuals should maintain euhydration (þ1% to –1%) for optimal exercise performance.36,62,64,7377 SOR: B
Fluid Replacement
9. Preseason or pre-event education to optimize ﬂuid
balance in athletes should be directed at athletes,
administrators, coaches, and event directors and should
include the following17,35,38,56,78,79:
a. The consequences of dehydration or ﬂuid overload.
b. Hydration-monitoring strategies.
c. How to use reliable and valid measures of pre-exercise
and postexercise body mass measurements to assess
ﬂuid status.
d. How to schedule activities and modify the rules ofplay to optimize hydration and improve safety.
e. Environmental inﬂuences on ﬂuid requirements.
SOR: C
10. Athletic trainers should educate physically active people,
the parents of physically active children, and coaches
about sweat rate, sweat-rate calculation, and how todevelop an individualized hydration plan.19,20,78,79 SOR: B
11. Athletic trainers or other health care providers should
help establish individualized hydration plans for physically active people (including those involved in team

Journal of Athletic Training879

sports). The plans should include rehydration strategies
that consider sweat rate, environment, acclimatization
state, body size, exercise duration, exercise intensity, andindividual ﬂuid preferences and tolerance.19,20,79 SOR: B
12. Gastric emptying (ie, how quickly ﬂuids exit the stomach)
is independently altered by ﬂuid volume, osmolality, pH,
carbohydrate type and concentration (if present in theﬂuid), exercise intensity, environmental stresses, ﬂuid
temperature, and the extent of hypohydration. Each ofthese variables should be considered when an individual
hydration strategy is developed.78,8084 SOR: B
13. Heat acclimatization affects the ﬂuid and electrolyte
requirements of physically active people. Sweat losses
increase and sweat-electrolyte concentrations decrease
with heat acclimatization.8589 Electrolyte losses may
increase or decrease depending on the relative magnitudeof each of these factors. Heat acclimatization should be afactor in developing individualized ﬂuid-replacement
plans. SOR: A
14. Water or other palatable ﬂuids should be easily accessible
before, during, and after activity.51,90 Athletes often prefercool, ﬂavored beverages; these should be available, whenpossible, to promote rehydration.51,91,92 SOR: B
15. Physically active individuals should refuel (ie, eat anddrink) within 2 hours of physical activity to replace ﬂuid,
electrolytes, carbohydrates, and protein.11,93106 SOR: B
16. Athletic trainers should develop policies that use
environmental-condition guidelines to determine workrest ratios and provide water breaks. They should
communicate with coaches and administrators to implement appropriate policies.107110 SOR: B

Hydration Assessment
22. Calculating body mass change is a quick and effective
way for the AT and other health care providers to track
hydration status over the course of 24 hours.130,131 Thismeasure is valid only when compared with at least 3
consecutive days of euhydrated baseline averagemass.132134 Body mass changes are also useful forassessing hydration status between practices on days withmultiple workouts and can help educate athletes regarding
individual ﬂuid needs. Body mass should be used as an
objective hydration measure by physically active individuals and clinicians to ensure maintenance of hydration
status. SOR: B
23. Assessment of the ﬁrst morning urine void increases thevalidity of hydration-status measurement.39,135140 Healthcare professionals should test the ﬁrst morning urine forurine speciﬁc gravity (USG), when feasible, to evaluate
hydration status. Spot urine samples at other times of the
day can be confounded by ﬂuid intake, exercise, and foodintake and may not be accurate indicators of hydration
status.137 SOR: B
24. Personal cues are important for individuals to gauge
their hydration status. Thirst sensation, void frequency,
and urine color are valuable indicators over the course ofa day or between days for obtaining a relative hydrationassessment.45,141 These factors should be addressed inhydration education and regarded as personal reminders
for individuals in their daily hydration maintenance.
SOR: C
Unique Situations

Beverage Additives
17. The athlete’s diet and rehydration beverages should
include sufﬁcient sodium (enough to replace losses but
not an excessive amount) to prevent or resolve imbalances that may occur as a result of sweat and urine
losses.10,19,93,111 SOR: B
18. Pre-exercise sodium ingestion can expand vascular ﬂuid
volumes.100,112 Ingesting sodium during activity delays
blood sodium decreases in some people87,88,113 but has alimited preventive effect in others.35,58,114,115 Sodium
supplementation before and during exercise should be
individualized based on speciﬁc losses and needs andshould be practiced. SOR: B
19. Caffeine may increase short-term urine production at rest
but does not induce diuresis during exercise.116118
Athletic trainers should not discourage mild or moderate(approximately 3 mg/kg: more than a cup of coffee for a
70-kg individual) caffeine consumption before and every
30 minutes during exercise on the basis of diuretic
effects.116121 SOR: A
20. Hyperhydration using glycerol is not recommended forathletes due to potential negative side effects (eg,headache, lightheadedness, nausea) and insufﬁcientevidence of performance beneﬁt.122127 SOR: B
21. Beverages with 4% alcohol content do not dehydrate
active people.128,129 However, beverages with greater
alcohol content facilitate excessive diuresis and should be
discouraged for ﬂuid replacement. SOR: B
880

Volume 52  Number 9  September 2017

25. At events (eg, road races, tournaments) that carry thepotential for athletes to develop hypohydration and EAH
during and after competition, appropriate personnel
should educate participants and staff in advance regarding
ﬂuid balance.142145 SOR: B
26. If moderate (2% to 5%) or severe (greater than 5%)
hypohydration is identiﬁed, oral ﬂuids should be administered. Only if oral ﬂuids are not tolerated or ﬂuid losses
are ongoing (from vomiting or diarrhea) should intravenous (IV) ﬂuids be administered by an appropriately
trained and licensed medical professional. In the absenceof a diagnosis beyond hypohydration, preventive IV ﬂuids
are not recommended. Administration of IV ﬂuids forsame-day return to play should be supervised by alicensed medical professional on-site who is responsible
for patient health and safety.2,146,147 SOR: B
27. Hypohydration and EAH are risk factors for exertional
rhabdomyolysis during physical activity and both canincrease its severity.67,68,148 Athletic trainers should
facilitate appropriate education and ﬂuid availability(eg, adequate but not excessive) to help athletes maintaineuhydration during physical activity. SOR: C
28. Hypohydration is a known predisposing factor forexertional sickling in those with sickle cell trait ordisease.59 Targeted education and hydration monitoring
are warranted for an athlete known to have sickle cell trait
or disease.149151 SOR: B
29. When determining an athlete’s weight-class eligibility,
hydration status should be assessed using a valid measure

of hydration status (eg, ﬁrst voided urine osmolality or
refractometer USG).90,152155 SOR: B
30. Whole-body sweat losses in children are less than in
adults, and children require different rehydration plans
than adults.24,55,156158 Hydration education is importantfor youth and adolescent athletes.19,20,79 Athletic trainers
should facilitate proper education based on individual
needs. SOR: B
31. Beyond age 50 years, a person’s thirst sensitivity
decreases with hypohydration and urine-concentrating
ability decreases.159 Extra consideration for hydration
should be directed toward these populations duringphysical activity.24,159,160 SOR: A
LITERATURE REVIEW
Fluid Balance and Regulation

The human body maintains total body water within anarrow range to preserve homeostasis. Individual ﬂuid
consumption varies from person to person at rest andbefore, during, and after exercise.1,39,40,161 Athletic trainers
should promote ﬂuid-balance habits that contribute to
overall health and the reduction of injury and illness.
Water is a major component of the human body,accounting for approximately 73% of lean body mass inyoung adults.162 Body water is distributed within cells(intracellular ﬂuid), between cells (interstitial ﬂuid), and inplasma (intravascular ﬂuid). At rest, approximately 40% of
the total body mass is intracellular ﬂuid, 15% is interstitialﬂuid, and 5% is intravascular ﬂuid.163 Water movement
between compartments is due to hydrostatic, osmotic(sodium and potassium), and oncotic (protein) pressures.
Sweat is hypotonic relative to body water, so elevatedextracellular tonicity results in water movement from theintracellular to extracellular (interstitial and intravascular)
spaces. As a consequence, all water compartments candehydrate with sweating, contributing to a total body-waterdeﬁcit and hypohydration.164,165 The resulting hypovolemic
hyperosmolality is thought to precipitate many of thephysiological consequences associated with hypohydration.
Importance of Maintaining Euhydration

Physiological Implications of Hypohydration. All
physiological systems in the human body are inﬂuenced
by hypohydration. The degree of hypohydration dictates theextent of systemic compromise. Isolating the physiologicalchanges that contribute to systemic compromise is difﬁcult,as an alteration in 1 system (eg, cardiovascular) inﬂuences
the function of other systems (eg, thermoregulatory,
muscular). In terms of thermoregulation, the bodybalances metabolic heat production and exogenous heataccumulation by transporting heat via the vascular system
to the body surface and dissipating it via conduction,
convection, evaporation, and radiation at the skin. The
relative contribution of each heat-transfer mechanism
depends on the environmental conditions and exercise
intensity.166170 Evaporation is the predominant heat-loss
mechanism during exercise in warm conditions.167,171 The
sweating response is therefore critical to maintaining bodytemperature during exercise in the heat. If water loss via
sweating occurs at a greater rate than ﬂuid consumption,

dehydration ensues, affecting both sweating and heattransport from working muscles.
During exercise, the body preferentially directs intravascular ﬂuids to (1) the brain for nutrition and oxygen
delivery, (2) the heart and lungs for blood circulation andgas exchange, (3) the peripheral sweat glands and bloodvessels for thermoregulation, and (4) the working muscles
for nutrition and oxygen delivery.7,30,61,71 More than 2%
hypohydration causes a decrease in sweat rate and sweating
onset.64 Severe hypohydration (greater than 5%) threatens
the ability to maintain normal body temperature, exercise
intensity, and vital organ function. A potential consequenceof hypohydration is a generally linear increase in coretemperature during physical activity, with core temperaturerising approximately 0.158C to 0.208C for every 1% ofbody weight lost (due to sweating) during activity.5,28,64
When a hypohydrated individual exercises, the added
thermal strain is due to both impaired skin blood
ﬂow64,71,172 and altered sweating responses.28,31,61 Thesethermoregulatory changes may negate the physiologicaladvantages resulting from increased ﬁtness and heatacclimatization, both of which increase plasma volume.
When combined with exercise, hypohydration decreases thesweating response, increases body temperature, and raises
the overall risk of heat illness.63,72
Thermal strain increases cardiovascular stress, which ischaracterized by decreased stroke volume, increased heartrate, increased systemic vascular resistance, and, as strain
progresses, decreased cardiac output.7,26,28,61,64 Similar tobody temperature changes, the magnitude of cardiovascularalterations is proportional to the degree of hypohydration.7
For example, heart rate increases 3 to 5 beats per minute forevery 1% decrease in body mass.60,69 The stroke-volume
reduction seen with hypohydration appears to be due toreduced central venous pressure, resulting from reduced
blood volume.7,28,30,64,71 Both hypovolemia and hypertonicity have been suggested as mechanisms for the alteredthermoregulatory and cardiovascular responses during
dehydration.
Additionally, hypohydration reduces heat tolerance andthe time to exhaustion during exercise; the latter also occurs
at lower core temperatures.29 Furthermore, hypohydration
is an etiologic factor in the onset of heat exhaustion andexertional heat stroke due to impairments in thermoregulation and cardiovascular compromise.65 Hypohydration
contributes to many conditions (eg, heat illness, cardiac
dysfunction) that reduce exercise performance and safety;
however, euhydration does not confer immunity to these
conditions. An in-depth review of heat illness duringphysical activity is presented in the NATA position
statement on exertional heat illnesses.65
Exercise-Associated Muscle Cramping. Hypohydration
has been hypothesized to contribute to the onset of
exercise-associated muscle cramps (EAMCs) via
contracted extracellular ﬂuid. 65 Long considered ahydration-related concern,173 EAMCs have now also been
linked to other causes.174177 The 2014 death of a football
player who drank approximately 4 gallons of water andsports drinks to relieve cramping178 demonstrates that
replacement strategies for athletes should be strictlysupervised and limited to replacement of actual losses.
Education for athletes and coaches must emphasize the lifethreatening risks of EAH. A more in-depth discussion of
Journal of Athletic Training

881

EAMCs can be found in the NATA position statement onexertional heat illnesses.65
Physiological Implications of Hyperhydration. If notpromptly recognized and appropriately treated, EAH ispotentially fatal via cerebral or noncardiogenic pulmonary
edema. This condition had been thought to be limited toendurance activities, such as marathons and the Ironman
triathlon,7 but the deaths of 2 high school football players
during the 2014 season178 emphasize the need for a better
understanding of this condition beyond the scope ofendurance medicine.
Although EAH occurs in 10% to 20% of sampled
marathon ﬁnishers, clinically signiﬁcant cases are relatively
uncommon.38,56,58,145 Signiﬁcantly low serum sodium levels
are identiﬁed more often in women than in men and after
activity that exceeds 4 hours in duration.38,56 Whenphysically active individuals adequately replace sodium
losses and do not consume excess ﬂuids, EAH is prevented.
Exercise-associated hyponatremia typically results fromingesting water or hypotonic beverages (including sports
drinks) beyond sweat losses.13,34,35 Often, renal water
clearance is inadequate due to inappropriate arginine
vasopressin release after exercise.179 Two common, often
additive scenarios are (1) ingesting water or hypotonic
beverages (including sports drinks) beyond sweat losses,
resulting in weight gain during exercise associated withinadequate renal water clearance,179 and (2) large sweat
sodium and water losses that are not adequately replaced orthat are replaced with hypotonic ﬂuids.34 Exercise-associated hyponatremia likely occurs on a continuum between
these opposite mechanisms.
Sweat sodium losses are generally low in heat-acclimatized athletes and probably do not play a large role in EAH
except in activities lasting a very long duration. 36
Ultimately, the extracellular ﬂuid space has a decreased
solute concentration compared with the intracellular ﬂuid
space, and water ﬂows into the cells to equalize soluteconcentrations across cell membranes, producing intracellular swelling. This, in turn, leads to physiologicaldysfunction at the cell, tissue, and organ-system levels,with most clinical signs reﬂecting intracranial pressurechanges and reduced oxygen exchange in the lungs. Deathfrom EAH is usually due to herniation of the brainstem.
Signs and symptoms of EAH normally present at serum
sodium levels ,130 mmolL –1 (range ¼ 109–131mmolL–1)115 and include milder early indications suchas lightheadedness, dizziness, nausea, pufﬁness of theextremities or face, muscle cramps that do not resolvewith the usual care, and body weight gain from baseline.
Severe later indications include altered mental status,
which may consist of disorientation, confusion, agitation,delirium, or feelings of ‘‘impending doom’’; obtundation;phantom running; seizures; coma; signs of herniation,such as decorticate posturing and mydriasis; and signs of
noncardiogenic pulmonary edema, such as dyspnea andfrothy sputum.35,38,56,58
Successful treatment of EAH associated with encephalopathy involves rapid sodium replacement in sufﬁcientamounts via hypertonic (3% or greater) saline IV infusion
to increase sodium concentration in the intravascular space,which draws water from the intracellular space. For mildcases of EAH, the patient should either be observed while
ﬂuids are withheld until he or she begins to urinate or
882

Volume 52  Number 9  September 2017

should ingest oral hypertonic ﬂuids or salty foods to shiftwater into the gut. Hypovolemic hyponatremic clinicalpresentations are rare but have been detected in athletesparticipating in endurance events.36,38 In the absence ofencephalopathy, these athletes may be cautiously rehydrated with normal saline, but their serum sodium levels should
be checked between liters of ﬂuid. If encephalopathy ispresent, treatment with IV hypertonic saline should beinitiated as described earlier.
Performance Implications of Hydration During
Exercise. Scientiﬁc debate continues with respect to theapparently discordant outcomes between ﬁeld-based andlaboratory studies of the effects of hypohydration on
exercise performance. Many laboratory studies havedemonstrated a consistent association between
hypohydration and decreased exercise performance.180,181
However, when the same variables were monitored in someuncontrolled ﬁeld studies, the data seemed to conﬂict.182185
When confounding variables were controlled in ﬁeld
studies, thermoregulation was markedly compromised,cardiovascular strain increased, and exercise performancedecreased with increased levels of hypohydration.4,5 Whenphysical activity takes place on a ﬁeld, the concepts thatgovern human physiological regulation of homeostasis
remain valid and cannot be ignored.
Endurance Performance. In studies of prolonged aerobic
activity, performance was consistently reduced whenhypohydration met or exceeded 2% body mass
loss.35,62,74,98,181,186 Physiologically, a decrease in theavailable body ﬂuid limits how much vascular volume isavailable for the delivery of nutrients and oxygen to
working muscles and the central nervous and cardiovascular systems.26,187 When ﬂuids are limited during physicalactivity, symptoms of dehydration and decreases in
performance become more apparent.
Abundant research4,5,19,62,70,74 has documented aerobic
performance decrements with hypohydration. Contradictory ﬁndings generally involved marginal levels (less than2%) of hypohydration or a lack of exercise-intensity
measures.23,75,188 Reductions in total body water decreasestroke volume and peripheral sweat gland perfusion.61
Therefore, in temperate and hot environments, performanceis decreased when hypohydration is greater than 2% bodymass.181 It has been demonstrated, however, that in coolenvironments74 or when thirst is mitigated,23 aerobic
performance can be maintained. Yet consuming ﬂuids
according to thirst alone does not maximize performance.189 At rest, increased thirst occurs when body masslosses approach 2%.48,50 During exercise, thirst signals at
similar water-loss thresholds appear to be absent or
ignored; this is referred to as voluntary dehydration.47
Furthermore, despite decreased performance with hypohydration, hyperhydration provides no performance beneﬁts
during endurance activity and increases the risk of
EAH.64,190192
Anaerobic Performance. Strength and power are important in some team and individual sports. The multifactorial
nature of these tasks makes it difﬁcult to isolate the effectsof hydration on performance. Still, when data are
combined, decrements in strength, power, and anaerobic
endurance are consistently apparent in athletes who are
more than 2% hypohydrated.76,193 Most studies193,194 thathave addressed the inﬂuence of hypohydration on muscle

Table 2. Sweat-Rate Equationa
Sweat loss (L) ¼ Body mass before exercise (kg) – Body mass after
exercise (kg) þ (Volume of fluid consumed during exercise [L]) –(Urine volume, if any [L])
Sweat rate (L/h) ¼ Sweat loss (L) / Exercise duration (h)aIf body mass is assessed in kilograms and fluid consumed in liters,
the sweat rate ¼ L/h.

function showed that a ﬂuid deﬁcit of 3% to 4% elicited aperformance decrement. Anaerobic performance research
related to hydration status is highly varied (eg, dehydrating
protocol, performance outcome, recovery timing),76 whichmakes it challenging to decipher the true mechanisms orspeciﬁc levels of hypohydration that cause decrements.
However, the data consistently support the likelihood thateuhydration improves anaerobic performance.
Cognitive Performance. Speciﬁc and rapid information
processing is necessary for quick and accurate decisions
and is fundamental to many sport and military activities.
Several investigations8,9,195198 demonstrated that a modest
level of hypohydration (greater than 1%) compromised
cognitive function, including task performance, reaction
time, short-term memory, and mood state. Yet most
impairments seem clinically negligible, and others contended that the effect of hypohydration on cognitive
function was limited.181,195,199,200 At similar hypohydrationlevels, women seemed to demonstrate fewer consistentcognitive impairments but more mood-state decrements
than men.8,9,139 Furthermore, heat exposure may induce amore profound negative effect of hypohydration on moodstate in both men and women.195,198,199
Fluid Replacement

Hydration safety for physically active individuals can beinﬂuenced by body ﬂuid status, but signiﬁcant variability
exists in factors such as habitual daily water intake,1,40
sweat rate,32,53,201 and gastrointestinal tolerance of consuming a large ﬂuid volume during exercise,202 whichmakes universal recommendations impossible. Ideally,
individual sweat-rate assessments should be performed
several times under realistic environmental conditions andat varying exercise intensities while wearing standard
clothing and equipment speciﬁc to the sport (Table 2).
Calculating an athlete’s sweat rate facilitates individual
education and an understanding of hydration status andﬂuid loss during activity that can be easily translated into anindividualized ﬂuid-replacement plan.19,20
With high-performance athletes, restricting dehydration
to no more than 2% body mass loss helps to maintain thephysiological, perceptual, and safety aspects of their
exercise while aiding in exercise recovery and subsequent
training sessions. Rehydration plans often need to bealtered during activity, and this is an important educational
component of hydration. Ideally, exercise-related body
ﬂuid losses should be replaced within a short time frame,and dietary intake should replace body fuels used during
exercise. Postexercise body mass losses generally require
replacement with 100% to 150% of calculated ﬂuid losses
due to ﬂuid bolus-initiated diuresis, particularly when ﬂuid
recovery time is limited (ie, less than 4 hours).203 When
recovery time is extended to more than 12 hours, balance isachieved with ad libitum food and ﬂuid consumption.

Most individuals can avoid ﬂuid-balance problems bydrinking when thirsty during and after exercise and eating ahealthy diet. In healthy individuals, the thirst mechanism isgoverned by a combination of serum osmolality andintravascular pressure as the body defends blood pressureand volume. Thirst typically increases at about 2%
hypohydration50 and markedly decreases when rehydration
restores this level. The 2% hypohydration threshold has
little effect on overall exercise performance in recreational
athletes and reduces the risk of EAH due to theoverconsumption of ﬂuids.
One anecdotal strategy used by many distance athletes in
an attempt to retain ﬂuid or prevent hyponatremia is sodium
tablets.204 Little evidence supports this practice for either
hyperhydration before activity205 or ﬂuid retention during
activity.204 Furthermore, adverse events associated with thispractice during activity are unknown.36
Competitive and recreational athletes who have chronic
medical conditions should consult their personal physicians
regarding hydration recommendations and strategies toavoid exacerbating their conditions.
Sweat-Rate Variability. Recommendations for people
participating in physical activity must be individualized.
For example, sweat rate can vary according to body size,
environmental conditions, exercise intensity, acclimatization status, and other factors.206 Reliable estimates of sweat
losses based on some of these variables exist32; however,they are not valid for every person and should only be used
as an estimate when speciﬁc calculations cannot be
conducted. Individual recommendations on ﬂuid replacement should be based on individual data and not population
estimates. In addition, competition goals and experiencemust be factored into ﬂuid-intake decision planning. A 50year-old participating in her ﬁrst marathon who has a 0.4
L/h sweat rate and a goal of ﬁnishing in 6 hours should notreceive the same hydration plan as a 28-year-old elite
male distance runner with a sweat rate greater than 2 L/h
who is attempting a 2.25-hour ﬁnish time in the same
event.
Robust individual variability exists in exercise-related
ﬂuid losses and the effect of hydration status on both
performance and well-being. Sweat rates for adults (.18years old) during exercise can range from 0.5 to 4.0
L/h,32,43,53,201,207,208 and measured sodium losses during
exercise range between 0.2 and 7.3 g/h.34,209212 Sweat
sodium concentrations, for example, range from 10 to 100
mEq/L, and these large variations require individual
replacement strategies. For athletes who have had hydration
complications (hypohydration or EAH) requiring medical
attention, formal assessment of sweat rate and sweatelectrolyte concentrations may be necessary to determine asafe individual replacement strategy.78
Fluid Intake Exclusive to Exercise. In terms of ﬂuids,
on average, free-living individuals habitually consume justover 2 L/d, with the typical range between 0.5 L/d and 4.0
L/d.1,42 Despite large individual variations in ﬂuid intake aswell as body water volume and hydration status, biomarkers
in the blood remain in a relatively tight range due to thewide normal range of urine-concentrating capacity.39,40,213
Exercise combined with individual variability in daily ﬂuid
needs makes normal ﬂuid intake ranges difﬁcult to establish
in athletes.1,40
Journal of Athletic Training

883

884

Volume 52  Number 9  September 2017

Due to a lack of fluid availability, try to
begin exercise 0.5% hyperhydrated
and ingest a little more fluid at halftime. This will limit body mass loss
and prevent .2% hypohydration at
game end. Slight hyperhydration for
an individual with proper oversightmay be beneficial in this case.
Body mass loss is likely affecting
performance and increasing
heat-illness risk during activity.
Increase fluid consumption andtry to approximate sweat rate
to avoid .2% (2.4-kg) bodymass loss during activity.

–1.5% Body mass (1.3 kg)
0.8 L
1.3 kg þ 0.8 L/1.5 h ¼ 1.4 L/hDrink when thirsty; may also
benefit from paying attention topersonal hydration cues before
exercise to ensure euhydration
rather than overhydration.

Postexercise hydration status
Fluid consumed
Sweat rate

Recommendation for similar
exercise–1% Body mass (0.8 kg)
0.4 L during race
0.8 kg þ 0.4 L/0.75 h ¼
1.6 L/hDoing a great job.
Finished the race at 1%
body mass loss.

–5% Body mass (6.0 kg)
2 L during breaks
6.0 kg þ 2.0 L/2.5 h ¼ 3.2 L/hYes
Soccer game (1.5 h)
Intermittent maximal
Euhydrated
Half-time (athletic administrators should
consider fluid breaks based on
environmental factors)–2.5% Body mass (1.5 kg)
0.5 L at half-time
1.5 kg þ 0.5 L/1.5 h ¼ 1.3 L/h
No
10-km Race (0.75 h)
MaximalEuhydrated
Every mile (1.6 km)
Yes
1.5 h
Mild/moderate (50%)
1% Hyperhydrated (85.9 kg)
When feasible

Yes
2.5-h PracticeIntermittent maximal
Euhydrated
Consistent breaks

28.3 (83)29 (84.2)
22 (71.6)
25 (77)

Wet-bulb globe temperature,
8C (8F)
Acclimatized to heat?
Exercise mode
Exercise intensity
Hydration status before activity
Available breaks

Individual D (Collegiate Soccer Player,
Female, 60 kg)
Individual C (Collegiate Football
Player, Male, 120 kg)
Individual B (Recreational
Runner, Male, 80 kg)
Individual A (Recreational Tennis
Player, Female, 85 kg)
Modifying Factor

Table 3. Sample Sweat-Rate Calculations

Factors Inﬂuencing Rehydration. The degree ofenvironmental heat stress is determined by temperature,
relative humidity, wind speed, and radiant energy load,
which induce physiological changes that affect rehydration
recommendations. Voluntary ﬂuid intake increases
substantially when ambient temperature rises above 258C;
however, the rehydration stimulus may be partiallypsychological.4749 Individual differences in learned
behavior also play a role in the rehydration process. An
athlete who knows from experience that rehydrating
enhances subsequent performance is more apt to consume
ﬂuid before signiﬁcant dehydration occurs, so appropriate
education of athletes is essential to success.79,214
The physical characteristics of a rehydration beveragecan dramatically inﬂuence ﬂuid replacement. Salinity,
color, sweetness, temperature, ﬂavor, carbonation, andviscosity all affect how much an individual drinks.51,91,140
Individuals exercising in the heat will voluntarily ingest
more ﬂuid if it is chilled.51,140 Because people ingest mostof their daily ﬂuids with meals, access to ample ﬂuids
during meals and adequate time to eat and drink will
improve rehydration.101,215
Hydration Before Exercise. The goal of an individual
hydration strategy is to maximize safety and performance
during exercise. It is important to begin an exercise bouteuhydrated. To ensure euhydration before activity, anathlete should be mindful of individual cues, such as thirst,
body weight, urine color, and voiding frequency. Individual variability exists in each of these cues, but all can
provide useful information regarding hydration levels.40,41,130,141,210,216 Competitive athletes may beneﬁt from
subtle hyperhydration (less than 2%) before exercise to
avoid more than a 2% body mass deﬁcit during activity.208
However, this recommendation should be pursued under
medical oversight and is advised only for athletes incompetitions and endurance events, when access to ﬂuids
is restricted due to remote locations, or sports in which
ﬂuid is not readily available (eg, soccer, trail races).
Recreational athletes should not need to consume extra
ﬂuids before activity but should begin exercise euhydrated.
Rehydration During Exercise. During exercise, the goal
for the physically active is to maintain hydration and notallow more than a 2% body mass loss.4,5,27,217 The
suggested ideal strategy for exercise performance advises
limiting body mass losses to less than 2% throughout
activity but not gaining weight during exercise.36,66 To
maintain euhydration during activity, an athlete should
consume enough ﬂuid to approximate personal sweat
volume losses and avoid both excessive body ﬂuid losses
and overconsumption of ﬂuids.66,79 A sample strategy forcalculating sweat loss and ﬂuid replacement is outlined inTable 3.
Thirst may be delayed, so for competitive athletes
striving to maximize performance, using a ‘‘drink whenthirsty’’ strategy may compromise performance.4 Therefore,
every individual should know his or her personal sweat rateand develop a hydration strategy based on individual
needs.19,20,66,78,79 An appropriate strategy promotes effective training and competition while maximizing safety.
However, a hydration plan may require short-term revisions
during competition based on unanticipated factors (eg,gastrointestinal upset, discomfort, ﬂuid availability, environmental conditions, ﬂuid type).
If athletes do not know their individual sweat rates,
drinking to thirst during activity most likely represents asafe strategy to prevent overdrinking. Drinking to thirstshould also be considered when exercising athletes cannot
follow their ideal plan for replacing ﬂuids at a rate similar
to their sweat rate.
Rehydration After Exercise. Rapidly replacing ﬂuids
after exercise restores euhydration, improves recovery,
reduces hypohydration symptoms, and decreases postexercise fatigue.* Up to 150% of the estimated ﬂuid deﬁcit
needs to be consumed to effectively replace ﬂuid losses
after exercise over a short recovery period (less than 4hours).100,101,203 This additional consumption is necessary
to compensate for the postexercise diuresis induced by thelarge ﬂuid load and restore normal arginine vasopressin
hormone levels in blood. The exact amount of ﬂuid needed
to restore euhydration depends on solid food composition
and the timing of food ingestion after exercise, as theelectrolyte and water contents of meals contribute to ﬂuid
replacement and can enhance ﬂuid retention.215
Beverage Additives

Under normal circumstances, physically active people
consuming a well-balanced diet should not need to add
speciﬁc ingredients to their ﬂuids before, during, or after
activity. As a general rule, those participating in physicalactivity lasting less than 1 hour should require no
substances other than water.34,220 Athletes participating in
exercise sessions lasting longer than 1 hour or including
intense intervals may beneﬁt from adding carbohydrates orelectrolytes (or both) to rehydration ﬂuids, especially inextreme environments.34,80,116,221224 Endurance athletes
may be aided by ﬂuids containing carbohydrates andelectrolytes during extended training bouts and competitions.82,100,116,221,224226 Individuals with much greater than
average sweat sodium concentrations (greater than 60 mEq/
L) and high sweat rates (greater than 2.5 L/h) may beneﬁt
from sodium supplementation in the ﬂuids consumed
during activity.34,51 However, no evidence indicates that
athletes are helped by sodium supplementation beyond
individual losses. Therefore, we recommend that individual
assessment of sweat-electrolyte concentrations should
occur before consideration is given to supplementing.
The goal of pre-exercise nutrition and hydration is tobegin exercise with adequate carbohydrate availability andbody water.222 Before physical activity, individual preferences determine hydration and diet choices.24,52,54,213,227,228
Gastric emptying, intestinal absorption, bowel transit time,and urine frequency vary for each individual.80,202,229,230
Competitive athletes can beneﬁt from carbohydrate-electrolyte beverages before activity.82,116,222,224 Physically
active people eating a balanced diet with adequate calories
and ﬂuids need not add ingredients to water to maintainhydration status. Beverages that appeal to individual taste
preferences may encourage individuals to drink more
ﬂuids.54,91,231 Adding carbohydrates or electrolytes (orboth, especially sodium) to the rehydration drink can help
maintain blood glucose, carbohydrate oxidation, andelectrolyte balance.220,232,233 In some cases, adding protein*References 82, 84, 93, 100, 113, 146, 147, 203, 218, 219.

to a sports drink may improve exercise performance.234
Rates of gastric emptying and intestinal absorption (theprimary site of ﬂuid absorption) inﬂuence rehydration,
especially during exercise.80,84,229 Fluid volume, ﬂuid
calorie content, ﬂuid osmolality, exercise intensity, environmental stress, and ﬂuid temperature are importantfactors that determine these rates. The single mostimportant variable may be the volume of ﬂuid in thestomach.84,229 Maintaining 400 to 600 mL of ﬂuid in thestomach optimizes gastric emptying.221,229 If carbohydrates
are included in the ﬂuid, the optimal concentration for ﬂuid
absorption is between 3% and 8%,221 but concentrations
greater than 5% to 8% may slow the rate.221,235 Exercise at
greater than 80% of VO2max may decrease the rate ofgastric emptying.229,236 Ingesting about 200 mL of ﬂuid
every 15 to 20 minutes may be ideal, but this timing can be
difﬁcult in sports with extended playing time between
breaks. Lastly, the rate of gastric emptying is slowed bysigniﬁcant hypohydration (greater than 4%), which complicates rehydration and may increase gastrointestinal
symptoms.83,202
To facilitate postexercise recovery, competitive athletes
may require more carbohydrates or electrolytes in their dietor ﬂuids to assist in ﬂuid balance. Ingesting carbohydrates
and protein after exercise provides substantial beneﬁts by
restoring muscle glycogen and facilitating muscle recovery,93,9698,237,238 and simultaneous carbohydrate and protein ingestion is better than ﬂuid alone for muscle and blood
glucose recovery.94,95,106 However, the optimal amount ofeither carbohydrate or protein has yet to be determined. The
overarching recommendation is to replace all ﬂuids andnutrients that were used or lost during exercise.
Caffeine does not compromise rehydration or increaseurine output when consumed in small quantities (up to 3
mg/kg) during or after exercise.116,118,119,121 Small amountsof caffeine in a rehydration beverage should not cause harmto the physically active postexercise.
Supplements containing creatine in various forms havebeen studied extensively due to purported dehydration andmuscle-cramping episodes in those who were actively
consuming them. At recommended doses, however,creatine does not compromise hydration status.239 Because
researchers have not investigated levels above the recommended dosages, no evidence is available regarding
hydration changes due to supplementation with greater
amounts of creatine.
The osmolyte glycerol has been used to increase body
water and potentially avoid hypohydration during events. In
controlled settings, glycerol promoted ﬂuid retention.122127
However, the excess ﬂuid in the body does not confer
consistent physiological or performance advantages.192
Furthermore, the side effects of glycerol (headache, nausea,etc) are quite common and not advantageous to physicalactivity.123,192,240
Alcohol inhibits arginine vasopressin release, andbeverages with an alcohol content above 2% reduce ﬂuid
retention during rehydration.128 However, in well-hydrated
individuals, rehydration with beverages containing up to
4% alcohol did not increase urine output.129 Research129
also suggests that the inﬂuence of hypovolemia on renal
ﬂuid retention is more potent than the diuretic effect of
alcohol. Drinks with increasing alcohol content (greater
Journal of Athletic Training885

than 4%) facilitate excessive diuresis and should be
discouraged for ﬂuid replacement.
Hydration Assessment

Hydration status is important yet often difﬁcult to assess
accurately and reliably in athletic settings. Measurement
techniques can indicate changes in hydration status241 but
should not be used to diagnose hypohydration. An
individual’s hydration state is in constant ﬂux and depends
on many factors; multiple indicators are needed foradequate assessment.66,78
Thirst. The perception of thirst at rest is accurately
quantiﬁed using the subjective thirst-sensation chart(ranging from 1 [not thirsty at all] to 9 [very, verythirsty]). This chart is widely used by researchers to support
thirst-sensation measures but not to quantify hydration
status. Normally, thirst increases when 2% hypohydration isapproached and decreases when ﬂuid balance is restored toa loss of less than 2%. This level may offer some protection
against EAH, although current evidence provides
insufﬁcient support. Furthermore, ﬁrst morning thirst is
strongly correlated with hypohydration as measured by anacute change in body mass.45
Body Mass. Measuring acute body mass changes using avalid and reliable ﬂoor scale is an efﬁcient hydrationassessment technique. Body mass is considered a valid
measure of hydration status only when losses are acutely
observed (eg, prepractice versus postpractice) 131 orcompared with a valid euhydrated baseline.181 A valid
baseline generally requires 3 consecutive days ofeuhydrated weight assessments to establish the normal
body mass that may be subject to circadian variation anddepends on the individual’s diet, digestion, ﬂuid intake, andbowel habits.131,133,216,242,243 Body mass assessment forhydration status is best used to show short-term changes
between pre-exercise and postexercise or changes in statusfrom baseline or in conjunction with other hydration
measurements.
Urine Concentration. The concentration and color ofurine vary inversely with its volume. As long as the ﬁrst
morning measurements of urine concentration are used toassess hydration, any one of them serves as an acceptablecomplement to body mass and thirst observations forassessing hydration.137 An important consideration whenassessing hydration is that urine volume and concentration
are affected not only by ﬂuid loss but also by activity, diet,and especially ﬂuid intake.137 The stability of urine
concentration as a measure of hydration assessment iscompromised by all of these variables. The most stablevalue, which provides a valid and reliable indication of
hydration status, is the ﬁrst morning assessment. When this is
not feasible, ATs should know that urine analysis may
confound the clinical decision-making process and that bodymass assessment provides more reliable information.137
Urine color is a popular assessment technique because it
is noninvasive, inexpensive, and reliable. The urine color
chart (available at www.hydrationcheck.com) demonstrated
good sensitivity and speciﬁcity compared with USG andosmolality measures.41,135,136 Urine color should be assessed after a sample is collected in a clear container andthen evaluated in adequate lighting without shadows.
Assessing color in the toilet bowl after urination is not
886

Volume 52  Number 9  September 2017reliable, as the sample is diluted with water and cannot be
accurately compared with the color chart. Urine color has
also demonstrated effectiveness as an educational tool forathletes to assess their own ﬂuid status.19,20,79 Lastly, aurine color of 8 on the chart indicates gross muscle damage
and myoglobin present in the urine (rhabdomyolysis or
kidney dysfunction); a patient presenting with this color
should receive prompt referral and follow-up testing.135,138
Urine speciﬁc gravity compares the concentration of aurine sample with that of distilled water and can bemeasured in several ways. Techniques include ﬂoating,handheld, optical, or digital refractometry as well as urine
reagent strips. Urine refractometry results are valid
compared with more complicated but time-tested measuresof urine concentration, such as urine osmolality.244
Refractometry is simple and requires only a small urine
sample and a relatively inexpensive (less than $300)
handheld device. Urine reagent strips are unreliable, evenwhen manufactured solely for hydration assessment,245 andare not recommended for this purpose.
Other Techniques. Additional techniques available for
estimating hydration status include urine and plasma or
serum osmolality assessments. However, these techniques
are time sensitive and require expensive equipment not
typically available in clinical or ﬁeld settings.241 An
osmometer is expensive (more than $3500) and requires
regular calibration and sophisticated maintenance.
Although urine osmolality is more valid and reliable thanother ﬁeld-accessible methods, 244 its cost typically
precludes use by ATs. Furthermore, obtaining a plasma or
serum sample requires much more equipment (needles,
tubes, centrifuge, etc) and phlebotomy training, again
restricting access to these measures by ATs. It is
important for the evidence-based practitioner tounderstand all hydration-assessment techniques andextrapolate results from only those studies thatincorporated multiple measures.
For the best estimate of hydration status in an athlete, 3
simultaneous measures are recommended: ﬁrst morning
urine color (or USG), thirst sensation, and body mass.137
All can be obtained in an athletic training facility witheasily accessed equipment and are reliable indicators ofhydration status. Body mass is best measured at the sametime each morning for valid comparisons.216 When bodymass is assessed both preactivity and postactivity, individuals can be educated on speciﬁc rehydration recommendations after activity.
Recognition of Hypohydration and Fluid Overload

The early signs and symptoms of exercise-related
hypohydration include thirst and general discomfort orcomplaints (approximately 2% body mass deﬁcit). These
are followed by ﬂushed skin, weariness, cramps, andapathy. At greater water deﬁcits (more than 2% body massloss), dizziness, headache, vomiting, nausea, heat sensations on the head or neck, chills, and dyspnea may bepresent (Table 1).50,57,139 The degree of hypohydration,
mental status, and general medical condition of the athlete
will dictate the mode, amount, type, and rate of recommended rehydration.
A potential difﬁculty in recognizing hydration abnormalities is that the signs and symptoms of hypohydration may

overlap those of EAH (Table 1).50,57,58,142,144 The earlysigns of EAH include headache, dizziness, physicalexhaustion, muscular twitching, and nausea, all of which
are also symptoms of hypohydration. Differential signs andsymptoms of EAH due to ﬂuid retention include weight
gain, history of overdrinking, extremity swelling, andprogressively worsening headache.38,142 Signs of encephalopathy generally occur when the sodium concentration isless than 125 mEqL–1 but have been documented with asodium concentration of 131 mEqL–1.115 More severe
encephalopathy is accompanied by altered mental status,
pulmonary edema, collapse, unconsciousness, seizure, andcoma. When these conditions cannot be differentiatedbased on the history and physical examination, a blood
sodium measurement is needed for accurate diagnosis,
which is imperative because either hypotonic or isotonic
ﬂuid given inappropriately to a patient with EAH can befatal. If point-of-care blood sodium assessment is notavailable for a patient with severe encephalopathy, theempiric administration of a hypertonic sodium IV can belife saving and will not harm a dehydrated individual.36
Unique Situations

Event Management. Medical professionals responsiblefor directing, supervising, and coordinating athletic eventsshould include hydration strategies in the medical andsafety plan. This includes estimating the maximum ﬂuid
volume needed for each participant in the event to optimize
both performance and safety. The event safety plan should
include athlete education opportunities for understanding
ﬂuid balance and should facilitate easy access to ﬂuids for
sweat-loss replacement. The event medical staff should betrained and equipped to assess athletes for dehydration,
EAH, and heat illness. Promotional and educational
materials provided to participants should include basic
deﬁnitions of hypohydration and hyperhydration,142 alongwith strategies to avoid both EAH (overconsumption) anddehydration during the event. Event managers should
consult experts in the planning stages to develop effective
strategies that reﬂect the event participants, environmental
conditions, resources, and medical support. Mass eventswith a high potential for participants to develop EAH or
dehydration should have a detailed medical plan toappropriately differentiate EAH, hypohydration,exertional heat stroke, and exercise-associated collapsethat includes point-of-care portable blood-electrolyte
analysis and rectal temperature measurement before
initiating treatment.59
Environmental Factors. The diuretic effects of moderate-altitude (greater than 2500 m) and high-altitude (greaterthan 3600 m) exposure have long been recognized by
mountaineers as a successful adaptation to altitude whereby
hemoconcentration (reduced plasma volume) improves
oxygen delivery to the tissues.246 The loss of water isself-limiting to approximately –2% of body mass and stems
primarily from the stimulation of peripheral arterial
chemoreceptors; the altitude-induced ﬂuid deﬁcit is notcorrected by increased ﬂuid consumption. In water sports(eg, swimming, water polo), diuresis occurs secondary to
ﬂuid shifts among compartments in the body induced byheat-conserving vasoconstriction.190,246 It is important tonote that hydration assessment immediately after exercise

in cool water is inaccurate and must be delayed. Whenphysical activity occurs in cold weather, the drive for thirstis blunted and ad libitum ﬂuid consumption is decreased.27,47,247 Furthermore, cold air (and the resulting
decreased skin temperature with peripheral vasoconstriction) induces a slight diuretic effect.33 Medical personnel
involved in the care of physically active individuals in thesesettings should be aware of particular nuances that may
affect recommendations to ensure athlete safety andperformance reasons.
Intravenous Fluids. Intravenous ﬂuids are used tocorrect symptomatic hypohydration when oral ﬂuids are
not tolerated or continued ﬂuid-electrolyte losses exceed
ﬂuid intake. Such IV ﬂuids are rarely necessary inotherwise healthy patients. Outcomes after rapid IV
rehydration suggest no lasting beneﬁts exceeding those oforal rehydration,218,248 and hormonal and ﬂuid balances are
facilitated by the oropharyngeal reﬂex and swallowing.146,147,219,249 Oral ﬂuids are recommended as the ﬁrstline rehydration strategy for most patients with exerciserelated hypohydration, although some recent evidence146,147
suggests that recovery from hypohydration (approximately
4% body mass loss) is most efﬁcient with the concomitant
use of IV and oral ﬂuids. When oral ﬂuids are not tolerated(because of vomiting, extreme nausea, or excessive
diarrhea), IV ﬂuids can be used as a primary intervention.
If EAH is suspected, a serum or blood sodium level shouldbe measured before oral or IV (hypotonic or isotonic) ﬂuid
is administered.
Sickle Cell Trait and Exertional Rhabdomyolysis.
Hypohydration is a known risk factor for an exertional
sickling episode.59 Hydration status should be part of theeducation process and then should be closely monitored inathletes known to have sickle cell disease or the sickle cell
trait. To facilitate safe participation, extra care is warranted
for these individuals to ensure adequate hydration status
before physical activity. 59 Conversely, exertional
rhabdomyolysis seems rather common in patients with
EAH.66 Although relatively novel in observation, truemechanisms have yet to be identiﬁed. Osmotic stress andexcessive muscle breakdown may be related.250 Therefore,
individual euhydration maintenance should be promoted toprevent exertional sickling as well as EAH and exertional
rhabdomyolysis.36
Weight-Certiﬁcation Recommendations. Many athletes
purposely dehydrate to qualify for lower weight classes (eg,wrestling, martial arts) or to meet physical appearance
expectations (eg, gymnastics). To discourage this unhealthy
practice, many state and national organizations require
weight certiﬁcation before or early in the competitive
season. Unfortunately, limited agreement exists among
governing bodies regarding a safe method to certify athletes
in speciﬁc weight classes.154,155,251,252 Best practice is fortrained medical professionals (eg, ATs, physicians) withestablished independent authority and freedom from teambias to determine the appropriate weight class based on theathlete’s best interest.153 Following are recommendations
for sport weight certiﬁcation:
1. All measures should be assessed using the ﬁrst morning
urine for the most validity.137 Use of other assessment
techniques or spot urine samples may result in misclassiﬁcation of hydration status.137

Journal of Athletic Training887

2. If USG is not ,1.025 (ﬁrst morning void), as quantiﬁed bya digital or clinical refractometer, body mass and body fat
should not be measured. The next measurement should
occur at least 24 hours later.
3. Body mass should be measured with a calibrated scale(60.2 lb [0.1 kg]).131,216
4. A trained technician should measure body fat. Becausesome of the available clinical measures are inﬂuenced byhydration status (eg, bioelectrical impedance, skinfolds),134,152,154,162,253 it is imperative that USG be assessedin conjunction with body mass and body fat assessment.

Exercise performance during intense or long-duration events
may be improved by adding carbohydrates and electrolytes
to rehydration beverages. Replacement ﬂuids may be morepalatable for athletes when chilled and when small amounts
of sodium and ﬂavoring are added. Education strategies forphysically active people should address personal sweat rates,
hydration cues, and rehydration strategies that avoid bothhypohydration and ﬂuid overload. These strategies will help
prevent hypohydration and EAH, maximize safety duringphysical activity, and optimize exercise performance.

Due to the many potential negative consequences of rapid
exercise-induced dehydration, the following practices
should be strongly discouraged for the purpose of ‘‘making
weight’’: impermeable or insulating clothing, excessive
exercise in a hot environment (steam room or sauna), ﬂuid
restriction, and purposeful fasting.66
Aging and Hydration. Under normal conditions of daily
life, ﬂuid intake is governed by multiple factors, includingthirst. Most large surveys show that daily ﬂuid consumption
is the same in healthy, independently living 65- to 80-yearold adults as in 20- to 35-year-old adults: approximately
21002400 mL/d.1,40,253 However, the timing of drinking
and beverage choices often vary in older adults. Less ﬂuid
is consumed in the evening hours, presumably to prevent
frequent nighttime urination.227 Dehydration in the elderly
often results from clinical conditions, medication use, or
accidental or disease-related ﬂuid deprivation or losses (or acombination of these).
The sensation of thirst is blunted in many but not all older
exercisers during and after exercise- or heat-induced
dehydration.227,228,254 Reduced thirst in the elderly isthought to be due to a diminished ability to sense a volume
deﬁcit (from hypotension or low blood volume) at thecentral level.254 With aging, osmoregulation remains intact
but central processing of signals by satiety centers in thebrain may change.254,255 Although healthy older adults
eventually restore all ﬂuid losses, this occurs at a slower
rate than in younger adults.253 This age effect is thought tobe progressive, yet the rate of decline appears to be highlyvariable and no longitudinal data are available.
Hydration is important for master’s athletes (older than
40 years) during the ﬁrst 5 days of heat acclimatization,
when plasma volume expansion occurs. This plasma
volume expansion requires increased ﬂuid intake. Twostudies159,160 examining plasma volume expansion during
early heat acclimation showed that many active adults
over age 50 may not adequately acclimate to exercise-heatstress due to inadequate postexercise and 24-hour ﬂuid
intake.

ACKNOWLEDGMENTS

SUMMARY

This position statement is intended to provide clinical ATs
with evidence-based hydration recommendations for physically active people. Individual safety and performance are
optimized when body mass losses are limited throughout
activity to 2% or less without total body water gains frombaseline. Competitive athletes striving for maximal performance may beneﬁt from a strategy based on replacing sweat
losses during prolonged activity. To reduce the risk of EAH,
athletes and recreational exercisers should only replace ﬂuid
lost in sweat during exercise and not gain ﬂuid weight.
888

Volume 52  Number 9  September 2017

Brendon P. McDermott, PhD, ATC, FACSM, serves on the
Medical and Science Advisory Board of the Korey Stringer
Institute (Storrs, CT) and the Advisory Board for the Kendrick
Fincher Hydration for Life foundation (Rogers, AR). Scott A.
Anderson, ATC, is a member of the Gatorade Sports Science
Institute’s Speaker Bureau (Barrington, IL). Lawrence E.
Armstrong, PhD, FACSM, is a consultant to, member of the
Scientiﬁc Advisory Board of, and has received grant funding from
Danone Research (Palaiseau, France); he is also a consultant to
the Drinking Water Research Foundation (Alexandria, VA).
Douglas J. Casa, PhD, ATC, FNATA, FACSM, is a consultant toGatorade (Chicago, IL); Clif Bar & Co (Emeryville, CA); Jones &Bartlett (Burlington, MA); UpToDate (Alphen aanden Rijn, The
Netherlands); Springer International Publishing AG (Berlin,
Germany); Lippincott Williams & Wilkins (Philadelphia, PA);
Quest Diagnostics (Madison, NJ); and Sports Innovation Lab(Boston, MA); a member of the Scientiﬁc Advisory Board of Clif
Bar & Co, the National Football League (New York, NY),
CamelBak (Petaluma, CA), Quest Diagnostics, Nix Inc (Boston,MA), and Sports Innovation Lab; and has received grant funding
from Gatorade; Kestrel Corporation; the National Football
League; HeartSmart.com (New Milford, CT); Mission ProductHoldings, Inc (New York, NY); Jones & Bartlett; Quest
Diagnostics; General Electric (Boston, MA); Nix Inc; the US
Air Force (Washington, DC); the US Army (Washington, DC);
Halo Wearables (San Francisco, CA); WHOOP, Inc (Boston,MA); the National Collegiate Athletic Association (Indianapolis,
IN); Danone Research; Timex Group USA, Inc (Middlebury, CT);
Eagle Pharmaceuticals, Inc (Woodcliff Lake, NJ); the National
Athletic Trainers’ Association (Carrollton, TX); the National
Center for Catastrophic Sport Injury Research (Chapel Hill, NC);
dhama Innovations Pvt Ltd (Hyderabad, India); and Polar Electro
Inc (Lake Success, NY). He has also provided expert testimony inapproximately 35 lawsuits since 2010. Samuel N. Cheuvront,
PhD, RD, FACSM, is a consultant to PepsiCo (Purchase, NY);
Nike (Beaverton, OR); Entrinsic Health Solutions, Inc (Norwood,MA); and Bitome, Inc (Boston, MA) and a member of the
Scientiﬁc Advisory Board of Bitome. Larry Cooper, MS, ATC, isa consultant to Gatorade. W. Larry Kenney, PhD, FACSM, is amember of the Scientiﬁc Advisory Board of the American
Council on Exercise (San Diego, CA) and has received grantfunding from Entrinsic Health Solutions, Inc, and the Dairy
Research Institute (St Paul, MN). Francis G. O’Connor, MD,
MPH, has no conﬂicts to declare. William O. Roberts, MD, MS,
FACSM, is a member of the Scientiﬁc Advisory Board of Race
Safe, SportzPeak Inc (San Francisco, CA).
We gratefully acknowledge the efforts of Aaron L. Baggish,
MD; Jennifer Doane, MS, RDN, CSSD, ATC; Greg Janik, MS,
ATC; Ron Maughan, PhD; Kevin C. Miller, PhD, ATC; and thePronouncements Committee in the preparation of this document.

DISCLAIMER
The NATA and NATA Research & Education Foundation
publish position statements as a service to promote the awarenessof certain issues to their members. The information contained inthe position statement is neither exhaustive nor exclusive to all
circumstances or individuals. Variables such as institutional
human resource guidelines, state or federal statutes, rules, or
regulations, as well as regional environmental conditions, may
impact the relevance and implementation of those recommendations. The NATA and NATA Foundation advise members andothers to carefully and independently consider each of therecommendations (including the applicability of same to any
particular circumstance or individual). The position statement
should not be relied upon as an independent basis for care but
rather as a resource available to NATA members or others.
Moreover, no opinion is expressed herein regarding the quality ofcare that adheres to or differs from the NATA and NATA
Foundation position statements. The NATA and NATA Foundation reserve the right to rescind or modify its position statements
at any time.

REFERENCES
1. Raman A, Schoeller DA, Subar AF, et al. Water turnover in 458
American adults 40-79 yr of age. Am J Physiol Renal Physiol.
2004;286(2):F394–F401. (Level of evidence [LOE]: 1)
2. Casa DJ, Ganio MS, Lopez RM, McDermott BP, Armstrong LE,
Maresh CM. Intravenous versus oral rehydration: physiological,
performance, and legal considerations. Curr Sports Med Rep.
2008;7(4):S41–S49. (LOE: 3)
3. Walsh RM, Noakes TD, Hawley JA, Dennis SC. Impaired highintensity cycling performance time at low levels of dehydration. Int
J Sports Med. 1994;15(7):392–398. (LOE: 2)
4. Bardis CN, Kavouras SA, Arnaoutis G, Panagiotakos DB, Sidossis
LS. Mild dehydration and cycling performance during 5-kilometerhill climbing. J Athl Train. 2013;48(6):741–747. (LOE: 2)
5. Casa DJ, Stearns RL, Lopez RM, et al. Inﬂuence of hydration on
physiological function and performance during trail running in theheat. J Athl Train. 2010;45(2):147–156. (LOE: 2)
6. MacLeod H, Sunderland C. Previous-day hypohydration impairs
skill performance in elite female ﬁeld hockey players. Scand J Med
Sci Sports. 2012;22(3):430–438. (LOE: 2)
7. González-Alonso J, Mora-Rodrı́guez R, Coyle EF. Stroke volume
during exercise: interaction of environment and hydration. Am J
Physiol Heart Circ Physiol. 2000;278(2):H321–H330. (LOE: 1)
8. Ganio MS, Armstrong LE, Casa DJ, et al. Mild dehydration impairscognitive performance and mood of men. Br J Nutr.
2011;106(10):1535–1543. (LOE: 1)
9. Armstrong LE, Ganio MS, Casa DJ, et al. Mild dehydration affects
mood in healthy young women. J Nutr. 2012;142(2):382–388.
(LOE: 1)
10. Vanderlei FM, Moreno IL, Vanderlei LC, Pastre CM, de Abreu LC,
Ferreira C. Comparison of the effects of hydration with water or
isotonic solution on the recovery of cardiac autonomic modulation.
Int J Sport Nutr Exerc Metab. 2015;25(2):145–153. (LOE: 2)
11. Bergeron MF, Laird MD, Marinik EL, Brenner JS, Waller JL.
Repeated-bout exercise in the heat in young athletes: physiologicalstrain and perceptual responses. J Appl Physiol (1985).
2009;106(2):476–485. (LOE: 2)
12. Farquhar WB, Morgan AL, Zambraski EJ, Kenney WL. Effects ofacetaminophen and ibuprofen on renal function in the stressedkidney. J Appl Physiol (1985). 1999;86(2):598–604. (LOE: 2)
13. Montain SJ, Sawka MN, Wenger CB. Hyponatremia associatedwith exercise: risk factors and pathogenesis. Exerc Sport Sci Rev.
2001;29(3):113–117. (LOE: 3)
14. Melin B, Jimenez C, Savourey G, et al. Effects of hydration state on
hormonal and renal responses during moderate exercise in the heat.
Eur J Appl Physiol Occup Physiol. 1997;76(4):320–327. (LOE: 2)
15. Osterberg KL, Horswill CA, Baker LB. Pregame urine speciﬁc
gravity and ﬂuid intake by National Basketball Association players
during competition. J Athl Train. 2009;44(1):53–57. (LOE: 2)

16. Volpe SL, Poule KA, Bland EG. Estimation of prepractice
hydration status of National Collegiate Athletic Association
Division I athletes. J Athl Train. 2009;44(6):624–629. (LOE: 2)
17. Yeargin SW, Casa DJ, Armstrong LE, et al. Heat acclimatizationand hydration status of American football players during initialsummer workouts. J Strength Cond Res. 2006;20(3):463–470.
(LOE: 3)
18. Yeargin SW, Casa DJ, Judelson DA, et al. Thermoregulatory
responses and hydration practices in heat-acclimatized adolescentsduring preseason high school football. J Athl Train.
2010;45(2):136–146. (LOE: 3)
19. Kavouras SA, Arnaoutis G, Makrillos M, et al. Educational
intervention on water intake improves hydration status andenhances exercise performance in athletic youth. Scand J Med Sci
Sports. 2012;22(5):684–689. (LOE: 2)
20. McDermott BP, Casa DJ, Yeargin SW, Ganio MS, Lopez RM,
Mooradian EA. Hydration status, sweat rates, and rehydration
education of youth football campers. J Sport Rehabil.
2009;18(4):535–552. (LOE: 2)
21. Armstrong LE, Johnson EC, Kunces LJ, et al. Drinking to thirst
versus drinking ad libitum during road cycling. J Athl Train.
2014;49(5):624–631. (LOE: 2)
22. Armstrong LE, Johnson EC, McKenzie AL, Ellis LA, Williamson
KH. Endurance cyclist ﬂuid intake, hydration status, thirst, andthermal sensations: gender differences. Int J Sport Nutr Exerc
Metab. 2016;26(2):161–167. (LOE: 3)
23. Berkulo MA, Bol S, Levels K, Lamberts RP, Daanen HA, Noakes
TD. Ad-libitum drinking and performance during a 40-km cycling
time trial in the heat. Eur J Sport Sci. 2016;16(2):213–220. (LOE:
2)
24. Rivera-Brown AM, Ramı́rez-Marrero FA, Wilk B, Bar-Or O.
Voluntary drinking and hydration in trained, heat-acclimatized girls
exercising in a hot and humid climate. Eur J Appl Physiol.
2008;103(1):109–116. (LOE: 2)
25. Yeargin SW, Finn ME, Eberman LE, Gage MJ, McDermott BP,
Niemann A. Ad libitum ﬂuid consumption via self- or external
administration. J Athl Train. 2015;50(1):51–58. (LOE: 2)
26. Montain SJ, Sawka MN, Latzka WA, Valeri CR. Thermal andcardiovascular strain from hypohydration: inﬂuence of exercise
intensity. Int J Sports Med. 1998;19(2):87–91. (LOE: 2)
27. Keneﬁck RW, Mahood NV, Hazzard MP, Quinn TJ, Castellani JW.
Hypohydration effects on thermoregulation during moderate
exercise in the cold. Eur J Appl Physiol. 2004;92(45):565–570.
(LOE: 2)
28. González-Alonso J, Mora-Rodrı́guez R, Below PR, Coyle EF.
Dehydration reduces cardiac output and increases systemic andcutaneous vascular resistance during exercise. J Appl Physiol(1985). 1995;79(5):1487–1496. (LOE: 1)
29. Sawka MN, Young AJ, Francesconi RP, Muza SR, Pandolf KB.
Thermoregulatory and blood responses during exercise at gradedhypohydration levels. J Appl Physiol (1985). 1985;59(5):1394–
1401. (LOE: 2)
30. Montain SJ, Coyle EF. Inﬂuence of graded dehydration on
hyperthermia and cardiovascular drift during exercise. J Appl
Physiol (1985). 1992;73(4):1340–1350. (LOE: 2)
31. Montain SJ, Latzka WA, Sawka MN. Control of thermoregulatory
sweating is altered by hydration level and exercise intensity. J Appl
Physiol (1985). 1995;79(5):1434–1439. (LOE: 2)
32. Gonzalez RR, Cheuvront SN, Ely BR, et al. Sweat rate prediction
equations for outdoor exercise with transient solar radiation. J Appl
Physiol (1985). 2012;112(8):1300–1310. (LOE: 2)
33. O’Brien C, Freund BJ, Sawka MN, McKay J, Hesslink RL, Jones
TE. Hydration assessment during cold-weather military ﬁeld
training exercises. Arctic Med Res. 1996;55(1):20–26. (LOE: 2)
34. Montain SJ, Cheuvront SN, Sawka MN. Exercise associatedhyponatraemia: quantitative analysis to understand the aetiology.
Br J Sports Med. 2006;40(2):98–105. (LOE: 3)

Journal of Athletic Training889

35. Hew TD, Chorley JN, Cianca JC, Divine JG. The incidence, risk
factors, and clinical manifestations of hyponatremia in marathon
runners. Clin J Sport Med. 2003;13(1):41–47. (LOE: 3)
36. Hew-Butler T, Rosner MH, Fowkes-Godek S, et al. Statement of the
3rd International Exercise-Associated Hyponatremia Consensus
Development Conference, Carlsbad, California, 2015. Br J Sports
Med. 2015;49(22):1432–1446. (LOE: 3)
37. Ebell MH, Siwek J, Weiss BD, Woolf SH, et al. Strength ofrecommendation taxonomy (SORT): a patient-centered approach tograding evidence in the medical literature. J Am Board Fam Pract.
2004;17(1):59–67.
38. Kipps C, Sharma S, Tunstall Pedoe D. The incidence of exerciseassociated hyponatraemia in the London marathon. Br J Sports
Med. 2011;45(1):14–19. (LOE: 3)
39. Perrier E, Demazieres A, Girard N, et al. Circadian variation andresponsiveness of hydration biomarkers to changes in daily water
intake. Eur J Appl Physiol. 2013;113(8):2143–2151. (LOE: 3)
40. Perrier E, Vergne S, Klein A, et al. Hydration biomarkers in freeliving adults with different levels of habitual ﬂuid consumption. Br
J Nutr. 2013;109(9):1678–1687. (LOE: 3)
41. Armstrong LE, Pumerantz AC, Fiala KA, et al. Human hydration
indices: acute and longitudinal reference values. Int J Sport Nutr
Exerc Metab. 2010;20(2):145–153. (LOE: 3)
42. Armstrong LE, Johnson EC, Casa DJ, et al. The American footballuniform: uncompensable heat stress and hyperthermic exhaustion. J
Athl Train. 2010;45(2):117–127. (LOE: 2)
43. Godek SF, Bartolozzi AR, Burkholder R, Sugarman E, Peduzzi C.
Sweat rates and ﬂuid turnover in professional football players: acomparison of National Football League linemen and backs. J Athl
Train. 2008;43(2):184–189. (LOE: 3)
44. Gonzalez RR, Cheuvront SN, Montain SJ, et al. Expanded
prediction equations of human sweat loss and water needs. J Appl
Physiol (1985). 2009;107(2):379–388. (LOE: 3)
45. Armstrong LE, Ganio MS, Klau JF, Johnson EC, Casa DJ, Maresh
CM. Novel hydration assessment techniques employing thirst and awater intake challenge in healthy men. Appl Physiol Nutr Metab.
2014;39(2):138–144. (LOE: 2)
46. Engell DB, Maller O, Sawka MN, Francesconi RN, Drolet L,
Young AJ. Thirst and ﬂuid intake following graded hypohydrationlevels in humans. Physiol Behav. 1987;40(2):229–236. (LOE: 2)
47. Greenleaf JE. Problem: thirst, drinking behavior, and involuntary
dehydration. Med Sci Sports Exerc. 1992;24(6):645–656. (LOE: 3)
48. Maresh CM, Gabaree-Boulant CL, Armstrong LE, et al. Effect ofhydration status on thirst, drinking, and related hormonal responses
during low-intensity exercise in the heat. J Appl Physiol (1985).
2004;97(1):39–44. (LOE: 2)
49. Takamata A, Mack GW, Gillen CM, Nadel ER. Sodium appetite,thirst, and body ﬂuid regulation in humans during rehydration
without sodium replacement. Am J Physiol. 1994;266(5, pt2):R1493R1502. (LOE: 2)
50. Shirreffs SM, Merson SJ, Fraser SM, Archer DT. The effects of
ﬂuid restriction on hydration status and subjective feelings in man.
Br J Nutr. 2004;91(6):951–958. (LOE: 2)
51. Burdon CA, Johnson NA, Chapman PG, O’Connor HT. Inﬂuence ofbeverage temperature on palatability and ﬂuid ingestion during
endurance exercise: a systematic review. Int J Sport Nutr Exerc
Metab. 2012;22(3):199–211. (LOE: 2)
52. Erdman KA, Tunnicliffe J, Lun VM, Reimer RA. Eating patterns
and composition of meals and snacks in elite Canadian athletes. Int
J Sport Nutr Exerc Metab. 2013;23(3):210–219. (LOE: 3)
53. Godek SF, Bartolozzi AR, Godek JJ. Sweat rate and ﬂuid turnoverin American football players compared with runners in a hot andhumid environment. Br J Sports Med. 2005;39(4):205–211. (LOE:
3)
54. O’Neal EK, Poulos SP, Bishop PA. Hydration proﬁle and inﬂuenceof beverage contents on ﬂuid intake by women during outdoor

890

Volume 52  Number 9  September 2017

recreational walking. Eur J Appl Physiol. 2012;112(12):3971–3982.
(LOE: 3)55. Rivera-Brown AM, Gutiérrez R, Gutiérrez JC, Frontera WR, Bar-Or
O. Drink composition, voluntary drinking, and ﬂuid balance inexercising, trained, heat-acclimatized boys. J Appl Physiol (1985).
1999;86(1):78–84. (LOE: 2)
56. Almond CS, Shin AY, Fortescue EB, et al. Hyponatremia among
runners in the Boston Marathon. N Engl J Med. 2005;352(15):1550–
1556. (LOE: 3)
57. Patel AV, Mihalik JP, Notebaert AJ, Guskiewicz KM, Prentice WE.
Neuropsychological performance, postural stability, and symptoms
after dehydration. J Athl Train. 2007;42(1):66–75. (LOE: 2)
58. Hoffman MD, Fogard K, Winger J, Hew-Butler T, Stuempﬂe KJ.
Characteristics of 161-km ultramarathon ﬁnishers developing exercise-associated hyponatremia. Res Sports Med. 2013;21(2):164–175.
(LOE: 2)
59. Casa DJ, Guskiewicz KM, Anderson SA, et al. National Athletic
Trainers’ Association position statement: preventing sudden deathin sports. J Athl Train. 2012;47(1):96–118. (LOE: 3)
60. Ganio MS, Wingo JE, Carroll CE, Thomas MK, Cureton KJ. Fluid
ingestion attenuates the decline in VO2peak associated withcardiovascular drift. Med Sci Sports Exerc. 2006;38(5):901–909.
(LOE: 2)
61. Sawka MN, Francesconi RP, Pimental NA, Pandolf KB. Hydrationand vascular ﬂuid shifts during exercise in the heat. J Appl Physiol
Respir Environ Exerc Physiol. 1984;56(1):91–96. (LOE: 2)
62. Ebert TR, Martin DT, Bullock N, et al. Inﬂuence of hydration statuson thermoregulation and cycling hill climbing. Med Sci Sports
Exerc. 2007;39(2):323–329. (LOE: 2)
63. Sawka MN, Young AJ, Latzka WA, Neufer PD, Quigley MD,
Pandolf KB. Human tolerance to heat strain during exercise:inﬂuence of hydration. J Appl Physiol (1985). 1992;73(1):368–375.
(LOE: 2)
64. Sawka MN, Montain SJ, Latzka WA. Hydration effects onthermoregulation and performance in the heat. Comp Biochem
Physiol A Mol Integr Physiol. 2001;128(4):679–690. (LOE: 2)
65. Casa DJ, DeMartini JK, Bergeron MF, et al. National Athletic
Trainers’ Association position statement: exertional heat illnesses. J
Athl Train. 2015;50(9):986–1000. (LOE: 3)
66. Sawka MN, Burke LM, Eichner ER, Maughan RJ, Montain SJ,
Stachenfeld NS. American College of Sports Medicine position
stand. Exercise and ﬂuid replacement. Med Sci Sports Exerc.
2007;39(2):377–390. (LOE: 3)
67. Bruso JR, Hoffman MD, Rogers IR, Lee L, Towle G, Hew-Butler T.
Rhabdomyolysis and hyponatremia: a cluster of ﬁve cases at the
161-km 2009 Western States Endurance Run. Wilderness Environ
Med. 2010;21(4):303–308. (LOE: 3)
68. Ellis C, Cuthill J, Hew-Butler T, George SM, Rosner MH. Case
report: exercise-associated hyponatremia with rhabdomyolysis
during endurance exercise. Phys Sportsmed. 2009;37(1):126–132.
(LOE: 3)
69. Adams WM, Ferraro EM, Huggins RA, Casa DJ. Inﬂuence of bodymass loss on changes in heart rate during exercise in the heat: asystematic review. J Strength Cond Res. 2014;28(8):2380–2389.
(LOE: 1)
70. Lopez RM, Casa DJ, Jensen KA, et al. Examining the inﬂuence of
hydration status on physiological responses and running speed
during trail running in the heat with controlled exercise intensity. J
Strength Cond Res. 2011;25(11):2944–2954. (LOE: 2)
71. Montain SJ, Coyle EF. Fluid ingestion during exercise increases
skin blood ﬂow independent of increases in blood volume. J Appl
Physiol (1985). 1992;73(3):903–910. (LOE: 2)
72. Carter R, Cheuvront SN, Williams JO, et al. Epidemiology of
hospitalizations and deaths from heat illness in soldiers. Med Sci
Sports Exerc. 2005;37(8):1338–1344. (LOE: 3)
73. Bigard AX, Sanchez H, Claveyrolas G, Martin S, Thimonier B,
Arnaud MJ. Effects of dehydration and rehydration on EMG

changes during fatiguing contractions. Med Sci Sports Exerc.
2001;33(10):1694–1700. (LOE: 2)
74. Cheuvront SN, Carter R, Castellani JW, Sawka MN. Hypohydration
impairs endurance exercise performance in temperate but not cold
air. J Appl Physiol (1985). 2005;99(5):1972–1976. (LOE: 2)
75. Dugas JP, Oosthuizen U, Tucker R, Noakes TD. Rates of ﬂuid
ingestion alter pacing but not thermoregulatory responses during
prolonged exercise in hot and humid conditions with appropriate
convective cooling. Eur J Appl Physiol. 2009;105(1):69–80. (LOE:
2)
76. Judelson DA, Maresh CM, Anderson JM, et al. Hydration andmuscular performance: does ﬂuid balance affect strength, power andhigh-intensity endurance? Sports Med. 2007;37(10):907–921.
(LOE: 3)77. Schoffstall JE, Branch JD, Leutholtz BC, Swain DE. Effects ofdehydration and rehydration on the one-repetition maximum benchpress of weight-trained males. J Strength Cond Res.
2001;15(1):102–108. (LOE: 2)
78. Maughan RJ, Shirreffs SM. Development of individual hydration
strategies for athletes. Int J Sport Nutr Exerc Metab.
2008;18(5):457–472. (LOE: 3)
79. Cleary MA, Hetzler RK, Wasson D, Wages JJ, Stickley C, Kimura
IF. Hydration behaviors before and after an educational andprescribed hydration intervention in adolescent athletes. J Athl
Train. 2012;47(3):273–281. (LOE: 2)
80. Jeukendrup AE, Moseley L. Multiple transportable carbohydrates
enhance gastric emptying and ﬂuid delivery. Scand J Med Sci
Sports. 2010;20(1):112–121. (LOE: 2)
81. Mudambo KS, Leese GP, Rennie MJ. Gastric emptying in soldiersduring and after ﬁeld exercise in the heat measured with the[13C]acetate breath test method. Eur J Appl Physiol Occup Physiol.
1997;75(2):109–114. (LOE: 2)
82. Clayton DJ, Evans GH, James LJ. Effect of drink carbohydratecontent on postexercise gastric emptying, rehydration, and thecalculation of net ﬂuid balance. Int J Sport Nutr Exerc Metab.
2014;24(1):79–89. (LOE: 2)
83. Ryan AJ, Lambert GP, Shi X, Chang RT, Summers RW, Gisolﬁ CV.
Effect of hypohydration on gastric emptying and intestinal absorption
during exercise. J Appl Physiol (1985). 1998;84(5):1581–1588.
(LOE: 2)84. Mitchell JB, Grandjean PW, Pizza FX, Starling RD, Holtz RW. The
effect of volume ingested on rehydration and gastric emptying
following exercise-induced dehydration. Med Sci Sports Exerc.
1994;26(9):1135–1143. (LOE: 2)
85. Taylor NA, Machado-Moreira CA. Regional variations in transepidermal water loss, eccrine sweat gland density, sweat secretion
rates and electrolyte composition in resting and exercising humans.
Extrem Physiol Med. 2013;2(1):4. (LOE: 3)
86. Allan JR, Wilson CG. Inﬂuence of acclimatization on sweat sodium
concentration. J Appl Physiol. 1971;30(5):708–712. (LOE: 2)
87. Buono MJ, Ball KD, Kolkhorst FW. Sodium ion concentration vs.
sweat rate relationship in humans. J Appl Physiol (1985).
2007;103(3):990–994. (LOE: 3)
88. Buono MJ, Claros R, Deboer T, Wong J. Naþ secretion rateincreases proportionally more than the Naþ reabsorption rate withincreases in sweat rate. J Appl Physiol (1985). 2008;105(4):1044–
1048. (LOE: 2)
89. Lorenzo S, Minson CT. Heat acclimation improves cutaneous
vascular function and sweating in trained cyclists. J Appl Physiol(1985). 2010;109(6):1736–1743. (LOE: 2)
90. Arnaoutis G, Kavouras SA, Angelopoulou A, et al. Fluid balance
during training in elite young athletes of different sports. J Strength
Cond Res. 2015;29(12):3447–3452. (LOE: 3)
91. Minehan MR, Riley MD, Burke LM. Effect of ﬂavor and awarenessof kilojoule content of drinks on preference and ﬂuid balance inteam sports. Int J Sport Nutr Exerc Metab. 2002;12(1):81–92.
(LOE: 2)

92. Wilmore JH, Morton AR, Gilbey HJ, Wood RJ. Role of taste
preference on ﬂuid intake during and after 90 min of running at 60%
of VO2max in the heat. Med Sci Sports Exerc. 1998;30(4):587–595.
(LOE: 2)
93. Desbrow B, Jansen S, Barrett A, Leveritt MD, Irwin C. Comparing
the rehydration potential of different milk-based drinks to acarbohydrate-electrolyte beverage. Appl Physiol Nutr Metab.
2014;39(12):1366–1372. (LOE: 2)
94. Naclerio F, Larumbe-Zabala E, Cooper R, Jimenez A, GossSampson M. Effect of a carbohydrate-protein multi-ingredientsupplement on intermittent sprint performance and muscle
damage in recreational athletes. Appl Physiol Nutr Metab.
2014;39(10):1151–1158. (LOE: 2)
95. Reidy PT, Konopka AR, Hinkley JM, Undem MK, Harber MP. The
effect of feeding during recovery from aerobic exercise on skeletal
muscle intracellular signaling. Int J Sport Nutr Exerc Metab.
2014;24(1):70–78. (LOE: 2)
96. Pritchett K, Bishop P, Pritchett R, Green M, Katica C. Acute effects
of chocolate milk and a commercial recovery beverage on
postexercise recovery indices and endurance cycling performance.
Appl Physiol Nutr Metab. 2009;34(6):1017–1022. (LOE: 2)
97. Gilson SF, Saunders MJ, Moran CW, Moore RW, Womack CJ,
Todd MK. Effects of chocolate milk consumption on markers ofmuscle recovery following soccer training: a randomized cross-overstudy. J Int Soc Sports Nutr. 2010;7:19. (LOE: 2)
98. Ferguson-Stegall L, McCleave EL, Ding Z, et al. Postexercise
carbohydrate-protein supplementation improves subsequent exercise performance and intracellular signaling for protein synthesis. J
Strength Cond Res. 2011;25(5):1210–1224. (LOE: 2)
99. Maughan RJ, Shirreffs SM. Recovery from prolonged exercise:
restoration of water and electrolyte balance. J Sports Sci.
1997;15(3):297–303. (LOE: 3)
100. Merson SJ, Maughan RJ, Shirreffs SM. Rehydration with drinks
differing in sodium concentration and recovery from moderate
exercise-induced hypohydration in man. Eur J Appl Physiol.
2008;103(5):585–594. (LOE: 2)
101. Shirreffs SM, Taylor AJ, Leiper JB, Maughan RJ. Post-exercise
rehydration in man: effects of volume consumed and drink
sodium content. Med Sci Sports Exerc. 1996;28(10):1260–1271.
(LOE: 2)102. Shirreffs SM, Maughan RJ. Volume repletion after exercise-induced
volume depletion in humans: replacement of water and sodium
losses. Am J Physiol. 1998;274(5, pt 2):F868F875. (LOE: 2)
103. Shirreffs SM, Maughan RJ. Rehydration and recovery of ﬂuid
balance after exercise. Exerc Sport Sci Rev. 2000;28(1):27–32.
(LOE: 3)104. Coyle EF. Timing and method of increased carbohydrate intake tocope with heavy training, competition and recovery. J Sports Sci.
1991;9:29–51. (LOE: 2)105. Burke LM, Collier GR, Davis PG, Fricker PA, Sanigorski AJ,
Hargreaves M. Muscle glycogen storage after prolonged exercise:effect of the frequency of carbohydrate feedings. Am J Clin Nutr.
1996;64(1):115–119. (LOE: 2)
106. Hill KM, Stathis CG, Grinfeld E, Hayes A, McAinch AJ. Coingestion of carbohydrate and whey protein isolates enhance PGC1a mRNA expression: a randomised, single blind, cross over study.
J Int Soc Sports Nutr. 2013;10(1):8. (LOE: 2)
107. Moyen NE, Mundel T, Du Bois AM, Ciccone AB, Morton RH,
Judelson DA. Increasing humidity affects thermoregulation during
low-intensity exercise in women. Aviat Space Environ Med.
2014;85(9):905–911. (LOE: 2)
108. Cooper ER, Ferrara MS, Broglio SP. Exertional heat illness andenvironmental conditions during a single football season in thesoutheast. J Athl Train. 2006;41(3):332–336. (LOE: 3)
109. Kulka TJ, Kenney WL. Heat balance limits in football uniforms:
how different uniform ensembles alter the equation. Phys
Sportsmed. 2002;30(7):29–39. (LOE: 2)

Journal of Athletic Training891

110. Hughson RL, Green HJ, Houston ME, Thomson JA, MacLean DR,
Sutton JR. Heat injuries in Canadian mass participation runs. Can
Med Assoc J. 1980;122(10):1141–1144. (LOE: 3)
111. Del Coso J, González-Millán C, Salinero JJ, et al. Effects of oral salt
supplementation on physical performance during a half-ironman: arandomized controlled trial. Scand J Med Sci Sports.
2016;26(2):156–164. (LOE: 2)
112. Armstrong LE, Costill DL, Fink WJ, et al. Effects of dietary sodium
on body and muscle potassium content during heat acclimation. Eur
J Appl Physiol Occup Physiol. 1985;54(4):391–397. (LOE: 2)
113. Moreno IL, Pastre CM, Ferreira C, de Abreu LC, Valenti VE,
Vanderlei LC. Effects of an isotonic beverage on autonomic
regulation during and after exercise. J Int Soc Sports Nutr.
2013;10(1):2. (LOE: 2)
114. Hoffman MD, Myers TM. Case study: symptomatic exerciseassociated hyponatremia in an endurance runner despite sodium
supplementation. Int J Sport Nutr Exerc Metab. 2015;25(6):603–
606. (LOE: 3)
115. Speedy DB, Noakes TD, Rogers IR, et al. A prospective study of
exercise-associated hyponatremia in two ultradistance triathletes.
Clin J Sport Med. 2000;10(2):136–141. (LOE: 3)
116. Ganio MS, Klau JF, Lee EC, et al. Effect of various carbohydrateelectrolyte ﬂuids on cycling performance and maximal voluntary
contraction. Int J Sport Nutr Exerc Metab. 2010;20(2):104–114.
(LOE: 1)117. Millard-Stafford ML, Cureton KJ, Wingo JE, Trilk J, Warren GL,
Buyckx M. Hydration during exercise in warm, humid conditions:effect of a caffeinated sports drink. Int J Sport Nutr Exerc Metab.
2007;17(2):163–177. (LOE: 1)
118. Wemple RD, Lamb DR, McKeever KH. Caffeine vs caffeine-free
sports drinks: effects on urine production at rest and during
prolonged exercise. Int J Sports Med. 1997;18(1):40–46. (LOE: 2)
119. Fiala KA, Casa DJ, Roti MW. Rehydration with a caffeinatedbeverage during the nonexercise periods of 3 consecutive days of 2a-day practices. Int J Sport Nutr Exerc Metab. 2004;14(4):419–429.
(LOE: 2)120. Ganio MS, Johnson EC, Klau JF, et al. Effect of ambient
temperature on caffeine ergogenicity during endurance exercise.
Eur J Appl Physiol. 2011;111(6):1135–1146. (LOE: 2)
121. Silva AM, Júdice PB, Matias CN, et al. Total body water and its
compartments are not affected by ingesting a moderate dose of
caffeine in healthy young adult males. Appl Physiol Nutr Metab.
2013;38(6):626–632. (LOE: 1)
122. Freund BJ, Montain SJ, Young AJ, et al. Glycerol hyperhydration:
hormonal, renal, and vascular ﬂuid responses. J Appl Physiol(1985). 1995;79(6):2069–2077. (LOE: 2)
123. Inder WJ, Swanney MP, Donald RA, Prickett TC, Hellemans J. The
effect of glycerol and desmopressin on exercise performance andhydration in triathletes. Med Sci Sports Exerc. 1998;30(8):1263–
1269. (LOE: 2)
124. Lyons TP, Riedesel ML, Meuli LE, Chick TW. Effects of glycerolinduced hyperhydration prior to exercise in the heat on sweating andcore temperature. Med Sci Sports Exerc. 1990;22(4):477–483.
(LOE: 2)125. Magal M, Webster MJ, Sistrunk LE, Whitehead MT, Evans RK,
Boyd JC. Comparison of glycerol and water hydration regimens on
tennis-related performance. Med Sci Sports Exerc. 2003;35(1):150–
156. (LOE: 2)
126. Montner P, Stark DM, Riedesel ML, et al. Pre-exercise glycerol
hydration improves cycling endurance time. Int J Sports Med.
1996;17(1):27–33. (LOE: 2)
127. O’Brien C, Freund BJ, Young AJ, Sawka MN. Glycerol
hyperhydration: physiological responses during cold-air exposure.
J Appl Physiol (1985). 2005;99(2):515–521. (LOE: 2)
128. Shirreffs SM, Maughan RJ. Restoration of ﬂuid balance after
exercise-induced dehydration: effects of alcohol consumption. J
Appl Physiol (1985). 1997;83(4):1152–1158. (LOE: 2)

892

Volume 52  Number 9  September 2017129. Hobson RM, Maughan RJ. Hydration status and the diuretic actionof a small dose of alcohol. Alcohol Alcohol. 2010;45(4):366–373.
(LOE: 2)130. Lew CH, Slater G, Nair G, Miller M. Relationship between changes
in upon-waking urinary indices of hydration status and body mass inadolescent Singaporean athletes. Int J Sport Nutr Exerc Metab.
2010;20(4):330–335. (LOE: 2)
131. Baker LB, Lang JA, Kenney WL. Change in body mass accurately
and reliably predicts change in body water after endurance exercise.
Eur J Appl Physiol. 2009;105(6):959–967. (LOE: 2)132. Muñoz CX, Johnson EC, Demartini JK, et al. Assessment ofhydration biomarkers including salivary osmolality during passive
and active dehydration. Eur J Clin Nutr. 2013;67(12):1257–1263.
(LOE: 2)133. Cheuvront SN, Ely BR, Keneﬁck RW, Sawka MN. Biologicalvariation and diagnostic accuracy of dehydration assessment
markers. Am J Clin Nutr. 2010;92(3):565–573. (LOE: 2)
134. Widjaja A, Morris RJ, Levy JC, Frayn KN, Manley SE, Turner RC.
Within- and between-subject variation in commonly measured
anthropometric and biochemical variables. Clin Chem.
1999;45(4):561–566. (LOE: 2)
135. Armstrong LE, Maresh CM, Castellani JW, et al. Urinary indices ofhydration status. Int J Sport Nutr. 1994;4(3):265–279. (LOE: 2)
136. McKenzie AL, Muñoz CX, Armstrong LE. Accuracy of urine color
to detect equal to or greater than 2% body mass loss in men. J Athl
Train. 2015;50(12):1306–1309. (LOE: 2)137. Cheuvront SN, Keneﬁck RW, Zambraski EJ. Spot urine concentrations should not be used for hydration assessment: a methodology
review. Int J Sport Nutr Exerc Metab. 2015;25(3):293–297. (LOE:
3)
138. Armstrong LE, Soto JA, Hacker FT, Casa DJ, Kavouras SA, Maresh
CM. Urinary indices during dehydration, exercise, and rehydration.
Int J Sport Nutr. 1998;8(4):345–355. (LOE: 2)
139. Pross N, Demazieres A, Girard N, et al. Inﬂuence of progressive
ﬂuid restriction on mood and physiological markers of dehydration
in women. Br J Nutr. 2013;109(2):313–321. (LOE: 2)
140. Armstrong LE, Johnson EC, Munoz CX, et al. Hydration
biomarkers and dietary ﬂuid consumption of women. J Acad Nutr
Diet. 2012;112(7):1056–1061. (LOE: 2)141. Burchﬁeld JM, Ganio MS, Kavouras SA, et al. 24-h void number as
an indicator of hydration status. Eur J Clin Nutr. 2015;69(5):638–
641. (LOE: 2)
142. Verbalis JG, Goldsmith SR, Greenberg A, et al. Diagnosis,
evaluation, and treatment of hyponatremia: expert panel recommendations. Am J Med. 2013;126(10 suppl 1):S1–S42. (LOE: 3)
143. Williams CA, Blackwell J. Hydration status, ﬂuid intake, andelectrolyte losses in youth soccer players. Int J Sports Physiol
Perform. 2012;7(4):367–374. (LOE: 2)
144. Hsieh M, Roth R, Davis DL, Larrabee H, Callaway CW.
Hyponatremia in runners requiring on-site medical treatment at asingle marathon. Med Sci Sports Exerc. 2002;34(2):185–189. (LOE:
2)
145. Kratz A, Siegel AJ, Verbalis JG, et al. Sodium status of collapsed
marathon runners. Arch Pathol Lab Med. 2005;129(2):227–230.
(LOE: 3)146. McDermott BP, Casa DJ, Lee EC, et al. The inﬂuence of
rehydration mode after exercise dehydration on cardiovascularfunction. J Strength Cond Res. 2013;27(8):2086–2095. (LOE: 2)147. McDermott BP, Casa DJ, Lee E, et al. Thermoregulation and stresshormone recovery after exercise dehydration: comparison of
rehydration methods. J Athl Train. 2013;48(6):725–733. (LOE: 2)
148. Chlı́bková D, Knechtle B, Rosemann T, et al. Rhabdomyolysis andexercise-associated hyponatremia in ultra-bikers and ultra-runners.
J Int Soc Sports Nutr. 2015;12:29. (LOE: 3)
149. Tripette J, Loko G, Samb A, et al. Effects of hydration anddehydration on blood rheology in sickle cell trait carriers during

exercise. Am J Physiol Heart Circ Physiol. 2010;299(3):H908–
H914. (LOE: 2)
150. Connes P, Reid H, Hardy-Dessources MD, Morrison E, Hue O.
Physiological responses of sickle cell trait carriers during exercise.
Sports Med. 2008;38(11):931–946. (LOE: 3)
151. Oh RC, Arter JL, Tiglao SM, Larson SL. Exertional rhabdomyolysis: a case series of 30 hospitalized patients. Mil Med.
2015;180(2):201–207. (LOE: 3)
152. Cutrufello PT, Dixon CB. The effect of acute ﬂuid consumption
following exercise-induced ﬂuid loss on hydration status, percent
body fat, and minimum wrestling weight in wrestlers. J Strength
Cond Res. 2014;28(7):1928–1936. (LOE: 2)
153. Lingor RJ, Olson A. Fluid and diet patterns associated with weight
cycling and changes in body composition assessed by continuous
monitoring throughout a college wrestling season. J Strength Cond
Res. 2010;24(7):1763–1772. (LOE: 2)
154. Utter AC, Lambeth PG. Evaluation of multifrequency bioelectrical
impedance analysis in assessing body composition of wrestlers.
Med Sci Sports Exerc. 2010;42(2):361–367. (LOE: 2)
155. Utter AC, McAnulty SR, Riha BF, Pratt BA, Grose JM. The validityof multifrequency bioelectrical impedance measures to detectchanges in the hydration status of wrestlers during acutedehydration and rehydration. J Strength Cond Res. 2012;26(1):9–15. (LOE: 2)
156. Bar-Or O. Effects of age and gender on sweating pattern during
exercise. Int J Sports Med. 1998;19(suppl 2):S106–S107. (LOE: 2)
157. Meyer F, Bar-Or O, MacDougall D, Heigenhauser GJ. Sweat
electrolyte loss during exercise in the heat: effects of gender andmaturation. Med Sci Sports Exerc. 1992;24(7):776–781. (LOE: 2)
158. Wilk B, Pender N, Volterman K, Bar-Or O, Timmons BW.
Inﬂuence of pubertal stage on local sweating patterns of girls
exercising in the heat. Pediatr Exerc Sci. 2013;25(2):212–220.
(LOE: 2)
159. Takamata A, Ito T, Yaegashi K, et al. Effect of an exercise-heatacclimation program on body ﬂuid regulatory responses to dehydration in older men. Am J Physiol. 1999;277(4, pt 2):R1041R1050.
(LOE: 2)160. Zappe DH, Bell GW, Swartzentruber H, Wideman RF, Kenney WL.
Age and regulation of ﬂuid and electrolyte balance during repeatedexercise sessions. Am J Physiol. 1996;270(1, pt 2):R71R79. (LOE:
2)
161. Sawka MN, Cheuvront SN, Carter R. Human water needs. Nutr Rev.
2005;63(6, pt 2):S30S39. (LOE: 3)
162. Wang Z, Deurenberg P, Wang W, Pietrobelli A, Baumgartner RN,
Heymsﬁeld SB. Hydration of fat-free body mass: review andcritique of a classic body-composition constant. Am J Clin Nutr.
1999;69(5):833–841. (LOE: 3)
163. Edelman IS, Leibman J. Anatomy of body water and electrolytes.
Am J Med. 1959;27(2):256–277. (LOE: 3)
164. Costill DL, Coté R, Fink W. Muscle water and electrolytes
following varied levels of dehydration in man. J Appl Physiol.
1976;40(1):6–11. (LOE: 2)
165. Nose H, Mack GW, Shi XR, Nadel ER. Role of osmolality andplasma volume during rehydration in humans. J Appl Physiol(1985). 1988;65(1):325–331. (LOE: 2)
166. Moyen NE, Ellis CL, Ciccone AB, et al. Increasing relative
humidity impacts low-intensity exercise in the heat. Aviat Space
Environ Med. 2014;85(2):112–119. (LOE: 2)
167. Shapiro Y, Pandolf KB, Avellini BA, Pimental NA, Goldman RF.
Heat balance and transfer in men and women exercising in hotdry
and hotwet conditions. Ergonomics. 1981;24(5):375–386. (LOE:
2)
168. Shapiro Y, Pandolf KB, Avellini BA, Pimental NA, Goldman RF.
Physiological responses of men and women to humid and dry heat. J
Appl Physiol Respir Environ Exerc Physiol. 1980;49(1):1–8. (LOE:
2)

169. Jay O, Bain AR, Deren TM, Sacheli M, Cramer MN. Large
differences in peak oxygen uptake do not independently alterchanges in core temperature and sweating during exercise. Am J
Physiol Regul Integr Comp Physiol. 2011;301(3):R832–R841.
(LOE: 2)170. Kenny GP, Jay O. Thermometry, calorimetry, and mean bodytemperature during heat stress. Compr Physiol. 2013;3(4):1689–
1719. (LOE: 3)
171. Candas V, Libert JP, Vogt JJ. Human skin wettedness andevaporative efﬁciency of sweating. J Appl Physiol Respir Environ
Exerc Physiol. 1979;46(3):522–528. (LOE: 2)
172. Binder K, Lynn AG, Gagnon D, Kondo N, Kenny GP. Hyperthermia modiﬁes muscle metaboreceptor and baroreceptor modulationof heat loss in humans. Am J Physiol Regul Integr Comp Physiol.
2012;302(4):R417–R423. (LOE: 3)
173. Bergeron MF. Heat cramps during tennis: a case report. Int J Sport
Nutr. 1996;6(1):62–68. (LOE: 3)
174. Schwellnus MP, Nicol J, Laubscher R, Noakes TD. Serum
electrolyte concentrations and hydration status are not associatedwith exercise associated muscle cramping (EAMC) in distancerunners. Br J Sports Med. 2004;38(4):488–492. (LOE: 3)
175. Schwellnus MP, Drew N, Collins M. Increased running speed andprevious cramps rather than dehydration or serum sodium changes
predict exercise-associated muscle cramping: a prospective cohort
study in 210 Ironman triathletes. Br J Sports Med. 2011;45(8):650–
656. (LOE: 3)
176. Maughan RJ. Exercise-induced muscle cramp: a prospective
biochemical study in marathon runners. J Sports Sci.
1986;4(1):31–34. (LOE: 3)
177. Parisi L, Pierelli F, Amabile G, et al. Muscular cramps: proposals
for a new classiﬁcation. Acta Neurol Scand. 2003;107(3):176–186.
(LOE: 3)178. Armstrong LE, McDermott BP, Hosakawa Y. Exertional hyponatremia. In: Casa DJ, Stearns RL, eds. Preventing Sudden Death inSport and Physical Activity. 2nd ed. Burlington, MA: Jones andBartlett Learning; 2017:219238. (LOE: 3)
179. Armstrong LE, Curtis WC, Hubbard RW, Francesconi RP, Moore
R, Askew EW. Symptomatic hyponatremia during prolonged
exercise in heat. Med Sci Sports Exerc. 1993;25(5):543–549.
(LOE: 3)180. Sawka MN, Noakes TD. Does dehydration impair exercise
performance? Med Sci Sports Exerc. 2007;39(8):1209–1217.
(LOE: 3)181. Cheuvront SN, Keneﬁck RW. Dehydration: physiology, assessment,
and performance effects. Compr Physiol. 2014;4(1):257–285.
(LOE: 3)182. Goulet ED. Dehydration and endurance performance in competitive
athletes. Nutr Rev. 2012;70(suppl 2):S132–S136. (LOE: 3)
183. Laursen PB, Suriano R, Quod MJ, et al. Core temperature andhydration status during an Ironman triathlon. Br J Sports Med.
2006;40(4):320–325. (LOE: 2)
184. Stachenfeld NS. The interrelationship of research in the laboratory
and the ﬁeld to assess hydration status and determine mechanisms
involved in water regulation during physical activity. Sports Med.
2014;44(suppl 1):S97–S104. (LOE: 3)
185. Maughan RJ. Investigating the associations between hydration andexercise performance: methodology and limitations. Nutr Rev.
2012;70(suppl 2):S128–S131. (LOE: 3)
186. Cheuvront SN, Carter R, Sawka MN. Fluid balance and endurance
exercise performance. Curr Sports Med Rep. 2003;2(4):202–208.
(LOE: 3)187. Cheuvront SN, Keneﬁck RW, Montain SJ, Sawka MN. Mechanismsof aerobic performance impairment with heat stress and dehydration. J Appl Physiol (1985). 2010;109(6):1989–1995. (LOE: 2)
188. Carvalho P, Oliveira B, Barros R, Padrão P, Moreira P, Teixeira
VH. Impact of ﬂuid restriction and ad libitum water intake or an 8%
carbohydrate-electrolyte beverage on skill performance of elite

Journal of Athletic Training893

adolescent basketball players. Int J Sport Nutr Exerc Metab.
2011;21(3):214–221. (LOE: 2)
189. Bardis CN, Kavouras SA, Kosti L, Markousi M, Sidossis LS. Mildhypohydration decreases cycling performance in the heat. Med Sci
Sports Exerc. 2013;45(9):1782–1789. (LOE: 2)
190. Maresh CM, Bergeron MF, Keneﬁck RW, Castellani JW, Hoffman
JR, Armstrong LE. Effect of overhydration on time-trial swim
performance. J Strength Cond Res. 2001;15(4):514–518. (LOE: 2)
191. Gigou PY, Dion T, Asselin A, Berrigan F, Goulet ED. Pre-exercise
hyperhydration-induced bodyweight gain does not alter prolonged
treadmill running time-trial performance in warm ambient conditions. Nutrients. 2012;4(8):949–966. (LOE: 2)
192. Goulet ED, Aubertin-Leheudre M, Plante GE, Dionne IJ. A metaanalysis of the effects of glycerol-induced hyperhydration on ﬂuid
retention and endurance performance. Int J Sport Nutr Exerc Metab.
2007;17(4):391–410. (LOE: 1)
193. Savoie FA, Keneﬁck RW, Ely BR, Cheuvront SN, Goulet ED.
Effect of hypohydration on muscle endurance, strength, anaerobic
power and capacity and vertical jumping ability: a meta-analysis.
Sports Med. 2015;45(8):1207–1227. (LOE: 3)
194. Judelson DA, Maresh CM, Farrell MJ, et al. Effect of hydration
state on strength, power, and resistance exercise performance. Med
Sci Sports Exerc. 2007;39(10):1817–1824. (LOE: 2)
195. Adam GE, Carter R, Cheuvront SN, et al. Hydration effects on
cognitive performance during military tasks in temperate and cold
environments. Physiol Behav. 2008;93(45):748–756. (LOE: 2)
196. Benefer MD, Corfe BM, Russell JM, Short R, Barker ME. Water
intake and post-exercise cognitive performance: an observational
study of long-distance walkers and runners. Eur J Nutr.
2013;52(2):617–624. (LOE: 3)
197. Grego F, Vallier JM, Collardeau M, Rousseu C, Cremieux J,
Brisswalter J. Inﬂuence of exercise duration and hydration status on
cognitive function during prolonged cycling exercise. Int J Sports
Med. 2005;26(1):27–33. (LOE: 2)
198. Lieberman HR, Bathalon GP, Falco CM, Kramer FM, Morgan CA,
Niro P. Severe decrements in cognition function and mood inducedby sleep loss, heat, dehydration, and undernutrition during
simulated combat. Biol Psychiatry. 2005;57(4):422–429. (LOE: 2)
199. Ely BR, Sollanek KJ, Cheuvront SN, Lieberman HR, Keneﬁck RW.
Hypohydration and acute thermal stress affect mood state but notcognition or dynamic postural balance. Eur J Appl Physiol.
2013;113(4):1027–1034. (LOE: 2)
200. Lieberman HR. Methods for assessing the effects of dehydration on
cognitive function. Nutr Rev. 2012;70(suppl 2):S143–S146. (LOE:
3)
201. Keneﬁck RW, Cheuvront SN, Elliott LD, Ely BR, Sawka MN.
Biological and analytical variation of the human sweating response:
implications for study design and analysis. Am J Physiol Regul
Integr Comp Physiol. 2012;302(2):R252–R258. (LOE: 2)
202. van Nieuwenhoven MA, Vriens BE, Brummer RJ, Brouns F. Effectof dehydration on gastrointestinal function at rest and during
exercise in humans. Eur J Appl Physiol. 2000;83(6):578–584.
(LOE: 2)203. Shirreffs SM, Aragon-Vargas LF, Keil M, Love TD, Phillips S.
Rehydration after exercise in the heat: a comparison of 4 commonlyused drinks. Int J Sport Nutr Exerc Metab. 2007;17(3):244–258.
(LOE: 2)204. Speedy DB, Thompson JM, Rodgers I, Collins M, Sharwood K,
Noakes TD. Oral salt supplementation during ultradistance exercise.
Clin J Sport Med. 2002;12(5):279–284. (LOE: 2)
205. Savoie FA, Asselin A, Goulet ED. Comparison of sodium chloride
tablets-induced, sodium chloride solution-induced, and glycerolinduced hyperhydration on ﬂuid balance responses in healthy men. J
Strength Cond Res. 2016;30(10):2880–2891. (LOE: 2)
206. Havenith G, van Middendorp H. The relative inﬂuence of physicalﬁtness, acclimatization state, anthropometric measures and gender894

Volume 52  Number 9  September 2017

on individual reactions to heat stress. Eur J Appl Physiol Occup
Physiol. 1990;61(56):419–427. (LOE: 2)
207. Gagnon D, Jay O, Kenny GP. The evaporative requirement for heatbalance determines whole-body sweat rate during exercise underconditions permitting full evaporation. J Physiol. 2013;591(11):2925–
2935. (LOE: 3)
208. Armstrong LE, Hubbard RW, Jones BH, Daniels JT. Preparing
Alberto Salazar for the heat of the 1984 Olympic marathon. Phys
Sportsmed. 1986;14(3):73–81. (LOE: 3)
209. Baker LB, Ungaro CT, Barnes KA, Nuccio RP, Reimel AJ, Stofan
JR. Validity and reliability of a ﬁeld technique for sweat Naþ andKþ analysis during exercise in a hot-humid environment. Physiol
Rep. 2014;2(5):e12007. (LOE: 2)
210. Maughan RJ, Merson SJ, Broad NP, Shirreffs SM. Fluid andelectrolyte intake and loss in elite soccer players during training. Int
J Sport Nutr Exerc Metab. 2004;14(3):333–346. (LOE: 2)
211. Shirreffs SM, Maughan RJ. Whole body sweat collection inhumans: an improved method with preliminary data on electrolyte
content. J Appl Physiol (1985). 1997;82(1):336–341. (LOE: 2)212. Patterson MJ, Galloway SD, Nimmo MA. Variations in regional
sweat composition in normal human males. Exp Physiol.
2000;85(6):869–875. (LOE: 2)
213. Perrier E, Rondeau P, Poupin M, et al. Relation between urinary
hydration biomarkers and total ﬂuid intake in healthy adults. Eur J
Clin Nutr. 2013;67(9):939–943. (LOE: 2)
214. Dabinett JA, Reid K, James N. Educational strategies used inincreasing ﬂuid intake and enhancing hydration status in ﬁeld
hockey players preparing for competition in a hot and humid
environment: a case study. Int J Sport Nutr Exerc Metab.
2001;11(3):334–348. (LOE: 2)
215. Maughan RJ, Leiper JB, Shirreffs SM. Restoration of ﬂuid balance
after exercise-induced dehydration: effects of food and ﬂuid intake.
Eur J Appl Physiol Occup Physiol. 1996;73(34):317–325. (LOE:
2)
216. Cheuvront SN, Carter R, Montain SJ, Sawka MN. Daily body mass
variability and stability in active men undergoing exercise-heatstress. Int J Sport Nutr Exerc Metab. 2004;14(5):532–540. (LOE: 2)
217. Charkoudian N, Halliwill JR, Morgan BJ, Eisenach JH, Joyner MJ.
Inﬂuences of hydration on post-exercise cardiovascular control inhumans. J Physiol. 2003;552(pt 2):635–644. (LOE: 2)
218. Casa DJ, Maresh CM, Armstrong LE, et al. Intravenous versus oral
rehydration during a brief period: responses to subsequent exercise
in the heat. Med Sci Sports Exerc. 2000;32(1):124–133. (LOE: 2)219. Casa DJ, Maresh CM, Armstrong LE, et al. Intravenous versus oral
rehydration during a brief period: stress hormone responses tosubsequent exhaustive exercise in the heat. Int J Sport Nutr Exerc
Metab. 2000;10(4):361–374. (LOE: 2)
220. Coyle EF, Montain SJ. Beneﬁts of ﬂuid replacement withcarbohydrate during exercise. Med Sci Sports Exerc. 1992;24(suppl
9):S324–S330. (LOE: 3)
221. Gisolﬁ CV, Lambert GP, Summers RW. Intestinal ﬂuid absorption
during exercise: role of sport drink osmolality and [Naþ]. Med Sci
Sports Exerc. 2001;33(6):907–915. (LOE: 2)
222. Kingsley M, Penas-Ruiz C, Terry C, Russell M. Effects ofcarbohydrate-hydration strategies on glucose metabolism, sprint
performance and hydration during a soccer match simulation inrecreational players. J Sci Med Sport. 2014;17(2):239–243. (LOE:
2)
223. Lee MJ, Hammond KM, Vasdev A, et al. Self-selecting ﬂuid intake
while maintaining high carbohydrate availability does not impair
half-marathon performance. Int J Sports Med. 2014;35(14):1216–
1222. (LOE: 2)
224. Meyer LG, Horrigan DJ, Lotz WG. Effects of three hydration
beverages on exercise performance during 60 hours of heat
exposure. Aviat Space Environ Med. 1995;66(11):1052–1057.
(LOE: 2)

225. Hill RJ, Bluck LJ, Davies PS. The hydration ability of threecommercially available sports drinks and water. J Sci Med Sport.
2008;11(2):116–123. (LOE: 2)
226. Siegler JC, Mermier CM, Amorim FT, Lovell RJ, McNaughton LR,
Robergs RA. Hydration, thermoregulation, and performance effectsof two sport drinks during soccer training sessions. J Strength Cond
Res. 2008;22(5):1394–1401. (LOE: 2)
227. Ferry M. Strategies for ensuring good hydration in the elderly. Nutr
Rev. 2005;63(6, pt 2):S22S29. (LOE: 3)228. Schols JM, De Groot CP, van der Cammen TJ, Olde Rikkert MG.
Preventing and treating dehydration in the elderly during periods ofillness and warm weather. J Nutr Health Aging. 2009;13(2):150–
157. (LOE: 2)
229. Horner KM, Schubert MM, Desbrow B, Byrne NM, King NA.
Acute exercise and gastric emptying: a meta-analysis andimplications for appetite control. Sports Med. 2015;45(5):659–
678. (LOE: 1)
230. Maughan RJ, Leiper JB, Vist GE. Gastric emptying and ﬂuid
availability after ingestion of glucose and soy protein hydrolysate
solutions in man. Exp Physiol. 2004;89(1):101–108. (LOE: 2)231. Wong SH, Sun FH. Effect of beverage ﬂavor on body hydration in
Hong Kong Chinese children exercising in a hot environment.
Pediatr Exerc Sci. 2014;26(2):177–186. (LOE: 3)232. Coyle EF, Montain SJ. Carbohydrate and ﬂuid ingestion during
exercise: are there trade-offs? Med Sci Sports Exerc.
1992;24(6):671–678. (LOE: 3)233. Coyle EF. Carbohydrate feeding during exercise. Int J Sports Med.
1992;13(suppl 1):S126–S128. (LOE: 3)234. Rustad PI, Sailer M, Cumming KT, et al. Intake of protein plus
carbohydrate during the ﬁrst two hours after exhaustive cycling
improves performance the following day. PLoS One.
2016;11(4):e0153229. (LOE: 3)235. Vist GE, Maughan RJ. Gastric emptying of ingested solutions in
man: effect of beverage glucose concentration. Med Sci Sports
Exerc. 1994;26(10):1269–1273. (LOE: 2)236. Leiper JB, Nicholas CW, Ali A, Williams C, Maughan RJ. The
effect of intermittent high-intensity running on gastric emptying of
ﬂuids in man. Med Sci Sports Exerc. 2005;37(2):240–247. (LOE: 2)
237. Breen L, Philp A, Witard OC, et al. The inﬂuence of carbohydrateprotein co-ingestion following endurance exercise on myoﬁbrillar
and mitochondrial protein synthesis. J Physiol. 2011;589(pt16):4011–4025. (LOE: 2)
238. Thomas DT, Erdman KA, Burke LM. Position of the Academy of
Nutrition and Dietetics, Dietitians of Canada, and the American
College of Sports Medicine: nutrition and athletic performance. J
Acad Nutr Diet. 2016;116(3):501–528. (LOE: 3)
239. Lopez RM, Casa DJ, McDermott BP, Ganio MS, Armstrong LE,
Maresh CM. Does creatine supplementation hinder exercise heat
tolerance or hydration status? A systematic review with metaanalyses. J Athl Train. 2009;44(2):215–223. (LOE: 2)240. Ross ML, Jeacocke NA, Laursen PB, Martin DT, Abbiss CR, Burke
LM. Effects of lowering body temperature via hyperhydration, withand without glycerol ingestion and practical precooling on cycling
time trial performance in hot and humid conditions. J Int Soc Sports
Nutr. 2012;9(1):55. (LOE: 2)
241. Armstrong LE. Hydration assessment techniques. Nutr Rev.
2005;63(6, pt 2):S40S54. (LOE: 3)242. Maughan RJ, Shirreffs SM, Leiper JB. Errors in the estimation of
hydration status from changes in body mass. J Sports Sci.
2007;25(7):797–804. (LOE: 2)
243. Fortes MB, Owen JA, Raymond-Barker P, et al. Is this elderly
patient dehydrated? Diagnostic accuracy of hydration assessment
using physical signs, urine, and saliva markers. J Am Med Dir
Assoc. 2015;16(3):221–228. (LOE: 2)244. Chadha V, Garg U, Alon US. Measurement of urinary concentration: a critical appraisal of methodologies. Pediatr Nephrol.
2001;16(4):374–382. (LOE: 3)245. Abbey BM, Heelan KA, Brown GA, Bartee RT. Validity ofHydraTrend reagent strips for the assessment of hydration status. J
Strength Cond Res. 2014;28(9):2634–2639. (LOE: 2)
246. Sawka M, Wenger C, Pandolf K. Thermoregulatory responses toacute exercise-heat stress and heat acclimation. In: Fregly M,
Blatteis C, eds. Handbook of Physiology. New York, NY: Oxford
Press; 1996:157–185. (LOE: 3)
247. Dann EJ, Gillis S, Burstein R. Effect of ﬂuid intake on renal
function during exercise in the cold. Eur J Appl Physiol Occup
Physiol. 1990;61(12):133–137. (LOE: 2)
248. Givan GV, Diehl JJ. Intravenous ﬂuid use in athletes. Sports Health.
2012;4(4):333–339. (LOE: 3)
249. Castellani JW, Maresh CM, Armstrong LE, et al. Endocrine
responses during exercise-heat stress: effects of prior isotonic andhypotonic intravenous rehydration. Eur J Appl Physiol Occup
Physiol. 1998;77(3):242–248. (LOE: 2)
250. Cairns RS, Hew-Butler T. Proof of concept: hypovolemichyponatremia may precede and augment creatine kinase elevations
during an ultramarathon. Eur J Appl Physiol. 2016;116(3):647–655.
(LOE: 2)251. Oopik V, Timpmann S, Burk A, Hannus I. Hydration status ofGreco-Roman wrestlers in an authentic precompetition situation.
Appl Physiol Nutr Metab. 2013;38(6):621–625. (LOE: 3)252. Pettersson S, Berg CM. Hydration status in elite wrestlers, judokas,
boxers, and taekwondo athletes on competition day. Int J Sport Nutr
Exerc Metab. 2014;24(3):267–275. (LOE: 3)253. Bossingham MJ, Carnell NS, Campbell WW. Water balance,
hydration status, and fat-free mass hydration in younger and older
adults. Am J Clin Nutr. 2005;81(6):1342–1350. (LOE: 2)
254. Kenney WL, Chiu P. Inﬂuence of age on thirst and ﬂuid intake. Med
Sci Sports Exerc. 2001;33(9):1524–1532. (LOE: 2)
255. Stachenfeld NS, Mack GW, Takamata A, DiPietro L, Nadel ER.
Thirst and ﬂuid regulatory responses to hypertonicity in older
adults. Am J Physiol. 1996;271(3, pt 2):R757R765. (LOE: 2)

Address correspondence to Brendon P. McDermott, PhD, ATC, FACSM, Athletic Training Program, Exercise Science ResearchCenter, University of Arkansas, 326B HPER Building, Fayetteville, AR 72701. Address e-mail to brendonm@uark.edu.

Journal of Athletic Training895