Effects of Oral Salt Supplementation on Physical Performance During a Half-ironman
Condition: Hyponatremia
MeSH terms: Hyponatremia
Study type: Interventional

Summary: 
      Background: Ultradistance athletes frequently consume salt supplements during competitions to
      compensate the loss of electrolytes by sweating. The aim of this study was to investigate the
      effectiveness of oral salt supplementation to improve exercise performance during a
      half-ironman triathlon. Methodology: Twenty-six experienced triathletes were matched for age,
      anthropometric data and training status and randomly placed into the salt group (113 mmol Na+
      and 112 mmol Cl-) or the control group (cellulose). The experimental treatments were provided
      in unidentifiable capsules and were ingested before and during the race. Participants
      competed in a real half-ironman triathlon and race time was measured by means of chip timing.
      Pre and post-race, body mass, maximal force during a whole-body isometric strength test,
      maximal height during a countermovement jump, and blood samples were obtained. Sweat samples
      were obtained during the running section.
    

Detailed description: 
      Participants Forty healthy and well-trained triathletes were recruited by email or through
      internet announcements to participate in this study. Before enrolling in the investigation, a
      questionnaire about their medical history, previous training, previous triathlon experience
      and best race time in half-ironman triathlon races was filled out by each participant.
      Potential participants with a previous history of muscle disorder, cardiac or kidney disease
      or those taking medicines during the two prior weeks were discarded. Finally, twenty-six
      participants were selected and matched (in pairs) for age, anthropometric data, training and
      best race time. Then, an equal number of triathletes (n = 13) was randomly assigned to the
      control group or to the salt ingestion group. Main morphological variables, training status
      and best performance time in the half-ironman distance were similar between these groups (P >
      0.05; Table 1). All the participants were informed of the risks and discomforts associated
      with the experiments and signed a written consent before their participation in this
      investigation. The study was approved by the Camilo Jose Cela Ethics Committee in accordance
      with the latest version of the Declaration of Helsinki.

      Experimental Protocol Participants were instructed to perform light exercise and to avoid
      pain-relieving strategies (e.g., analgesic medications, manual massage, ice, etc) the two
      days before the race. In addition, participants were instructed to avoid any sources of
      caffeine and alcohol 24 h before the onset of the race. Three hours before the race,
      participants arrived at an area close to the start line having drunk 500 mL of tap water two
      hours before arrival. Participants had their habitual pre-competition meal and it was not
      standardized among participants to avoid affecting participants' pre-competition routines.
      However, the pre-competition meals were analyzed afterwards and their content in
      carbohydrates, proteins and salt was similar between groups.

      On arrival, participants rested for 10 minutes in a recumbent chair and a 5-mL venous blood
      sample was drawn from an antecubital vein. The blood was allowed to clot and centrifuged at
      5000g to obtain serum. Participants then completed a 10-min standardized warm-up consisting
      of running, dynamic leg exercises and practice jumps. After that, participants performed two
      countermovement vertical jumps (CMJ) for maximal height on a force platform (Quattrojump,
      Kistler, Switzerland) to assess pre-race leg power output. On command, the participant flexed
      their knees and jumped as high as possible while maintaining the hands on the waist and
      landed with both feet. The highest values for jump height and the peak muscle leg power
      during the concentric phase of the jump were used for statistical analysis. Participants were
      previously familiarized with the jump test.

      After that, whole-body isometric muscle strength was measured by means of a hand-held pull
      gauge (Isocontrol Isométrico, EV-Pro, Spain) set at a frequency of 1000 Hz. For this
      measurement, participants stand on a 50 × 50 cm iron base connected to a handle-bar by a
      non-elastic cable. The isometric gauge was inserted within the cable and the height of the
      cable was individually set to provide a 135º knee flexion while the back and the arms were
      completely extended. Participants were instructed to perform a maximal pull by for 3-s using
      their whole body (mainly legs and arms) while maintaining this position. Verbal motivation
      was provided during the test. An adjustable lumbar-back protector was used for support and
      protection during the execution. Maximal and mean isometric strength were obtained during the
      test. Participants were previously familiarized with this measurement.

      After that, participants were provided with 3 plastic bags each one containing 4 white
      capsules (e.g., a total of 12 capsules). In the salt group, the capsules were filled with a
      commercially available product that contains buffered electrolyte salts (Saltstick caps,
      Saltstick, California US). The total amount of electrolytes provided in the salt group was:
      2580 mg of sodium (113 mmol), 3979 mg of chloride (112 mmol), 756 mg of potassium (19.3 mmol)
      and 132 mg of magnesium (5.4 mmol). In the control group, participants received the same
      number of capsules with the exact same appearance but filled with an isocaloric placebo
      (cellulose). All the participants were instructed to ingest the contents of the first bag in
      the transition between the swimming and cycling sections, the second bag around the middle of
      the cycling leg and the third bag during the transition between the cycling and running
      sections. This schedule was used to facilitate ingestion and electrolyte absorption during
      the race. Participants received a sample of these capsules (filled with placebo) the week
      before the race to practice the ingestion protocol during the transition and the cycling
      sector. Participants were encouraged to ingest all the capsules in the programmed schedule
      and to report any incidence during the capsule ingestion throughout the race.

      Just 15-min before the race (and after their habitual warm-up), participants were weighed in
      their competition clothes (without wetsuit) and a segmental bioelectrical impedance analysis
      was performed (BC-418, Tanita, Japan) to predict pre-to-post race total body water changes.
      The race started at 12:00 h and consisted of 1.9 km of swimming, 75 km of cycling (1100 m net
      increase in altitude) and 21.1 km of running. Environment conditions were recorded at 30-min
      intervals and mean ± SD (range) dry temperature during the event was 22.5 ± 2.7ºC (18.8 -
      26.6 ºC) with a relative humidity of 36.8 ± 8.3% (32 - 45%). The swim section was performed
      in a natural lake with water temperature at 17.5 ± 0.3ºC. All participants wore a neoprene
      wetsuit during the swim section. Participants drank and consumed food ad libitum and swam,
      cycled and ran at their own pace with no instructions given by the experimenters (apart from
      those related to capsule ingestion).

      During the second transition (between the cycling and running legs), two sweat patches
      (Tegaderm+Pad, 3M, US) were placed on the forearm to collect sweat samples. For this purpose,
      participants went to an area located just outside the transition area and the forearm skin
      was cleaned with distilled water and alcohol and dried with clean gauze to eliminate any
      remains of previous sweat from the skin. After this, the sweat patch was firmly adhered to
      the skin and fastened by an elastic tubular net bandage (Elastofix, Insfarma, Germany). This
      process took approximately 1-min and this time was subtracted from the final race time of
      each participant.

      Within 1-min of the end of the race, participants went to a finish area and body mass and
      body bioelectrical impedance were immediately measured using the same apparatus described
      previously. Participants were instructed to avoid drinking from the finish line till the
      post-race weighing and an experimenter assured compliance. Then, participants performed two
      countermovement vertical jumps and the whole-body isometric muscle strength test, as
      previously described. These performance tests were completed within 5-min of the end of the
      race. Participants then rested for 5-min and a venous blood sample was obtained. During this
      resting period, the sweat patches were removed using clean tweezers and placed in a sterile
      10 mL- tube. Sweat patches that were detached from the skin or presented a leak were
      discarded.

      After these protocols, the rate of perceived exertion during the race was self-rated using
      the Borg scale (6 to 20 points) while perceived leg muscle soreness was self-rated using a
      visual analog scale (0 to 10 points). Participants also filled out a detailed questionnaire
      about fluid and food intake during the race. Data on this questionnaire were used to
      calculate fluid, calorie and carbohydrate intake during the race. With this self-reported
      questionnaire, we also calculated electrolyte intake during the race (apart from the salt
      ingested with the capsule treatment). Finally, participants reported any incident during the
      intake of the capsules and the side-effects derived from their ingestion.

      Blood and sweat sample analysis The blood was allowed to clot in situ and serum was separated
      by centrifugation (10 min at 5000 g) and frozen at -80ºC until the day of analysis. At a
      later date, the serum portion was analyzed for osmolality (1249, Advance 3MO, Spain), sodium,
      chloride, potassium and magnesium concentrations (Nova 16, NovaBiomedical, Spain). In
      addition, the serum creatine kinase concentration was measured as a blood marker of muscle
      damage by means of an autoanalyzer (AU5400, Beckman Coulter, US). The sweat was separated
      from the patches by centrifugation (10 min at 3000 g), transferred to 5-mL sealed tubes and
      refrigerated at 4 ºC. At a later date (within 2 days of the race), sweat osmolality was
      measured with the same osmometer employed for the serum samples while sweat electrolyte
      concentration were measured using an ion selective electrode analyzer (Cobas 6000, Roche,
      Madrid, Spain).

      Statistical Analysis The normality of each variable was initially tested with the
      Shapiro-Wilk test. All the variables presented a normal distribution. For the variables
      obtained once during the experiment (race time, body mass change, sweat electrolyte
      concentration, self-rated fatigue and muscle soreness, etc) the comparison between groups
      (salt vs control) was performed using Student's t test for independent samples. For the
      variables obtained twice during the experiment (body mass, blood variables, jump performance,
      etc) the comparison between groups was performed by using a mixed model ANOVA (time ×
      treatment) with repeated measures for the variable time. The data were analyzed with the
      statistical package SPSS version 19.0 (SPSS Inc., Chicago, IL). The significance level was
      set at P < 0.05. Data are presented as mean ± SD.
    

Intervention name(s): Salt administration; Placebo administration
Intervention type(s): Dietary Supplement; Dietary Supplement
Intervention description(s): Participants were provided with 3 plastic bags each one containing 4 white capsules (e.g., a total of 12 capsules). In the salt group, the capsules were filled with a commercially available product that contains buffered electrolyte salts (Saltstick caps, Saltstick, California US). The total amount of electrolytes provided in the salt group was: 2580 mg of sodium (113 mmol), 3979 mg of chloride (112 mmol), 756 mg of potassium (19.3 mmol) and 132 mg of magnesium (5.4 mmol). In the control group, participants received the same number of capsules with the exact same appearance but filled with an isocaloric placebo (cellulose). All the participants were instructed to ingest the contents of the first bag in the transition between the swimming and cycling sections, the second bag around the middle of the cycling leg and the third bag during the transition between the cycling and running sections.
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Double (Participant, Investigator)
Primary purpose: Basic Science
Keywords: Half-ironman; Triathlon; Salt; Exercise; Performance