bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparing for and competing in the heat: the human perspective
Authors: MAUGHAN R. J. , LINDINGER M. I. 
Published: June 2010

SummaryThis review provides an overview of the challenges that face man and horses when exercising in the heat. Some of the strategies that are used and are being developed for human atheletes exercising in the heat are reviewed. There are many similarities between human and equine physiological responses to exercise in the heat; and equine exercise science may gain some useful insights from the training, fluid replacement and heat acclimatisation strategies used by human athletes. There are, however, some important differences that impact on the ability of horses to thermoregulate and to regulate fluid and electrolyte balance. The major differences are the low surface area to body mass ratio in horses compared to man; and the high metabolic capacity of equine skeletal muscle. These 2 factors may limit the ability of horses to dissipate heat when exercise is performed under hot conditions. Some of the more important equine differences are highlighted within the context of the ‘human perspective’.
Electrolyte and total protein changes in nonheat acclimated horses performing treadmill exercise in cool (20°C/40% RH), hot, dry (30°C/40% RH) or hot, humid (30°C/80% RH) conditions
Authors: HARRIS PATRICIA A. , MARLIN D. J. , SCOTT C. M. , HARRIS R. C. , MILLS P. C. , MICHELL A. R. , ORME C. E. , ROBERTS C. A. , SCHROTER R. C. , MARR CELIA M. , BARRELET F. 
Published: June 2010

SummaryFour horses (H, J, N and M) undertook a simulated competition exercise test (CET), designed to simulate physiological and metabolic stresses of the Speed and Endurance (S & E) test of a 3‐day‐event, under 3 different environmental conditions: 20°C/40% relative humidity (RH) (cool, dry [CD] 2 sessions); 30°C/40%RH (hot, dry [HD]) and 30°C/80%RH (hot, humid [HH]) (Marlinet al.1995a). Venous blood samples for electrolyte and total protein (TP) determinations were collected from indwelling catheters at predetermined time points throughout each CET and initial 30 min recovery period. Venous blood samples were collected by jugular venepuncture at 2 h and 24 h after the end of the final 8 min canter (Phase D). The effects of exercise, environmental condition and horse on venous TP, sodium (Na+), potassium (K+), chloride (Cl−), calcium (Ca2+), magnesium (Mg2+) and phosphate (PP43‐) plasma concentrations were investigated. In addition, the effect of environmental condition on estimated cation loss was evaluated.All horses completed the full CET under the CD and HD conditions, but only one horse completed the full 8 min of the final canterPhase Dunder HH conditions. Exercise had a significant (P<0.05) effect on all parameters similar to those reported previously in field competitions. There was a significant (P<0.05) interaction between time and horse for TP, Na+and Cl−. Overall, the environmental condition had a significant (P<0.05) effect on all parameters, but the differences were not considered to be of any physiological relevance, other than for Cl−and TP. There was a significant (P<0.05) interaction between time and environmental condition for Cl−and TP only. During much of the CET and recovery period, mean Cl−values were higher with the first CD session than the second CD session or under the HH or HD conditions. For TP after 2 min ofPhase Dand during the initial recovery period, concentrations were higher under the HH conditions and returned to the Pre‐ values less quickly. There were marked individual variations in the estimated cation losses and no consistent effect of environmental condition was found. Although estimated fluid loss was similar following both HD and HH sessions, restoration of bodyweight was slower following the CET studies under HH conditions.
Physiological responses of horses competing at a modified 1 Star 3‐day‐event
Authors: KOHN CATHERINE W. , HINCHCLIFF K. W. , McCUTCHEON L. J. , GEOR R. , FOREMAN J. , ALLEN A. K. , WHITE SUSAN L. , MAYKUTH PATRICIA L. , WILLIAMSON LISA H. 
Published: June 2010

SummaryThe impending 1996 summer Olympic 3‐day‐event in Atlanta has focused attention on the need to determine what modifications to the demanding Endurance Test will be required to ensure safety of the horses competing. Three groups of horses participated in a Field Trial held in August of 1994 in northern Georgia to determine the safety and feasibility of conducting a modified 3‐day‐event in hot, humid weather. One group (TD) completed a modified 1 Star 3‐day‐event test, a control group (HT) completed a Horse Trial identical to the modified 1 Star test except for the omission ofPhases BandCand the third group (E), comprised of European horses, completed the modified 1 Star test with a longer, fasterPhase Cthan was used for TD.During the Endurance Test, the ambient temperature and relative humidity ranged from 24.3°C and 98.9% in the morning to 30.2°C and 51.6% in the afternoon. No horse failed to complete the Trial because of heat stress or fatigue. There were no significant (P<0.05) differences detected in heart rate, rectal temperature, respiratory rate or net weight loss between HT and TD horses at any observation time. The highest rectal temperature recorded at the end ofPhase Cwas 39.6°C. These findings suggest that the modified 1 Star Endurance Test was as well tolerated by American horses as the control Horse Trial test. Rectal temperature was significantly higher for E than for TD or HT at the finish ofPhase C.European horses had significantly greater decreases in weight than HT and TD at the end ofPhases CandDand the next day. These findings probably reflect the faster and longer work effort of E horses duringPhase C.Modification ofPhase Cand the rest‐pause to ensure that recovery and heat dissipation occurred before the start ofPhase Dresulted in a 3‐day‐event that was safe for horses. The Field Trial provides a model for designing a modified Olympic Endurance Test. If the 1996 Olympic 3‐day‐event is held in hotter and more humid weather than the Field Trial, additional modifications to the Endurance Test (decreased distances, speeds and numbers of jumping efforts) will probably be required to ensure safety of competing horses.
Acid:base and serum biochemistry changes in horses competing at a modified 1 Star 3‐day‐event
Authors: HINCHCLIFF K. W. , KOHN CATHERINE W. , GEOR R. , McCUTCHEON L. J. , FOREMAN J. , ANDREWS F. M. , ALLEN A. K. , WHITE SUSAN L. , WILLIAMSON LISA H. , MAYKUTH PATRICIA L. 
Published: June 2010

SummaryWe examined the effects of participation in each of 3 modifications of Day 2 of a 3‐day‐event on blood and serum variables indicative of hydration, acid:base status and electrolyte homeostasis of horses. Three groups of horses − 8 European (E) horses and 2 groups each of 9 North American horses performed identical Days 1 (dressage) and 3 (stadium jumping) of a 3‐day‐event. E horses and one group of the North American horses (TD) performed modifications of Day 2 of a 1 Star 3‐day‐event and the other group of North American horses (HT) performed a Horse Trial on Day 2. Jugular venous blood was collected from each horse on the morning of Day 2 before any warm‐up activity, between 4 min 55 s and 5 min 15 s afterPhase Dand the following morning. Eight E horses, 5 TD horses and 8 HT horses completed the trials. There were few significant differences in acid:base or serum biochemistry variables detected among horses performing either 2 variations of the Speed and Endurance day of a 1 Star 3‐day‐event, or a conventional Horse Trial. Failure to detect differences among groups may have been related to the low statistical power associated with the small number of horses, especially in the TD group, variation in quality of horses among groups and the different times of the day at which the E horses competed. Differences detected among time points were usually common to all groups and demonstrated metabolic acidosis with a compensatory respiratory alkalosis, a reduction in total body water and cation content, and hypocalcaemia. Importantly, horses of all groups did not replenish cation, chloride, and calcium deficits after 14–18 h of recovery.
Water and ion losses during the cross‐country phase of eventing
Authors: ECKER GAYLE L. , LINDINGER M. I. 
Published: June 2010

SummaryLoss of total body water and ions during prolonged exercise can predispose the horse to health and performance problems. This study examined total body water (TBW) losses and extracellular (ECF) ion losses during the crosscountry (XC) phase of Preliminary, Intermediate and Advanced Horse Trials and CCI level 3‐day‐events. Jugular venous blood samples and body mass (BM) were collected on 49 horses at rest, Pre‐XC, Post‐XC and following 30 min of recovery. Plasma was separated from blood cells within 10 min of collection. Plasma was analysed for [Na+], [K+], [Cl−], ionised [Ca++], [glucose], [lactate] and packed cell volume (PCV) and plasma [protein] ([PP]). Distances ranged from 3000–6000 m for the XC phase with speeds of 500–570 m/min. In general, losses of TBW, Na+and Cl−increased with increasing level of difficulty. Loss of TBW Post‐XC ranged from 2–6.1% of resting values or 8.9–12.6 litres for the Preliminary level to mean ± s.e. 20.4 ± 1.8 litres for CCI. Losses of ECF ions ranged from 0.5–6.4% for Na+, 1.2–7.7% for Cl−, gains of 8% to losses of 23% for K+, and gains of 7% to losses of 11.7% for Ca++at 30 min Post‐XC. There was little recovery following 30 min and deficits of 5.3 ± 2.5 litres persisted overnight in horses that were tested. Plasma protein and PCV increased Post‐XC and PCV remained elevated above resting values at 30 min recovery. It is concluded that significant water and ion losses occur and, in general, increase with increased level of difficulty. There was little change with 30 min of recovery and for some horses losses persisted overnight.
Physiological measurements in horses after strenuous exercise in hot, humid conditions
Authors: ART TATIANA , VOTION DOMINIQUE , LEKEUX R. 
Published: June 2010

SummaryThe purpose of this study was 1) to measure and compare some physiological parameters in horses during a standardised treadmill exercise performed either in temperate atmospheric conditions (TC) (ambient temperature: 15°C; relative humidity: 55%), or in hot and humid conditions (HHC) (ambient temperature: 30°C; relative humidity: 75%) and 2) to follow the recovery of the same horses during 1 h after both tests. Five healthy fit Standardbred horses were investigated twice at 8 days interval, in TC and in HHC. Some measurements were made during a standardised treadmill exercise test (SET), others during a 1 h recovery period. The SET consisted of 8 min warm‐up and 8 min exercise.During the SET, respiratory airflow and O2and CO2fraction in the respiratory gases were continuously recorded, using 2 ultrasonic pneumotachographs connected to a face mask and a mass spectrometer. Oxygen uptake (V̇O2), carbon dioxide output, respiratory quotient and expired minute volume (V̇E) were obtained on a breath‐by‐breath basis. The maximal values obtained during the highest intensity of the SET and the values obtained 2 min after the end of the test were used for the comparison between both tests. Heart rate (HR) and skin temperature were continuously recorded, using a heart rate recording system and a real time infrared thermographic unit, respectively. After both SETs in TC and HHC, the horses recovered in TC. Heart rate, respiratory frequency (f) and rectal temperature were regularly measured during 1 h after the test. Venous blood was sampled after the completion of the test for biochemical analysis, namely plasma electrolytes and enzymatic activities.Exercising in HHC induced a reduction of the aerobic metabolism to the total energy requirement, i.e. a 20% decrease of V̇O2and 55% increase in lactate, as well as a decrease in V̇E. The increase in rectal and skin temperature, the dehydration and the weight loss were higher in HHC than in TC. During the recovery period the HR and f remained higher up to 30 min after the end of the SET in HHC while the rectal temperature remained higher up to 60 min after the end of this test. Therefore, despite the fact that our horses recovered in TC after exercising in HHC, there were significant differences between their physiological parameters measured during the recovery. This means that the recovery in air‐conditioned unit would probably be an insufficient measure to ensure an adequate cooling of the horses and justify consequently the adaptations proposed by the Federation Equestre Internationale (FEI), i.e. the decrease of the distance of the run and the increase of the time devoted to the halt between phases.
The effects of tonicity, glucose concentration and temperature of an oral rehydration solution on its absorption and elimination
Authors: LEÓN L. A. SOSA , DAVIE A. J. , HODGSON D. R. , ROSE R. J. 
Published: June 2010

SummaryEffects of different tonicities, glucose concentrations and temperatures of an oral rehydration solution (ORS) on its uptake and elimination in resting horses were studied. Fluid and electrolyte deficits similar to those occurring during prolonged exercise were induced by the administration of 1 mg/kg bwt of frusemide i.m., 3 h prior to the ORS. Fluid was administered via nasogastric tube at a volume equivalent to 4% bodyweight, which approximated diuretic induced losses. The uptake of fluid was evaluated by changes in haematocrit (PCV) and plasma total protein concentration (TP). Changes in electrolyte balance were studied by measurements of plasma and urinary electrolyte concentrations while changes in bodyweight, urine volume and faecal water content were used to estimate retention of the administered fluids. Changes in acid base status were assessed from venous blood bicarbonate values. Fluid tonicity had a major effect on the uptake and elimination of the ORS. The hypertonic fluid (628 mOsm/kg bwt) was less rapidly absorbed and resulted in more rapid fluid and electrolyte excretion than the isotonic (314 mOsm/kg bwt) and hypotonic (water) fluids. The inclusion of glucose did not enhance the absorption of the ORS, although fluids containing higher concentrations of electrolytes resulted in more rapid elimination of fluid in urine. There was a direct relationship between higher concentrations of sodium in the ORS, plasma sodium values and osmolality. Fluid temperature (5, 21 and 37°C) had no demonstrable effect on absorption of the ORS and elimination of fluids post administration.We concluded that while glucose concentration and fluid temperature have minimal effects on fluid absorption and elimination, fluid tonicity was a key element in the uptake and elimination of orally administered fluid. These findings are likely to be of relevance when administering ORS in association with exercise.
Sweating rate and sweat composition during exercise and recovery in ambient heat and humidity
Authors: McCUTCHEON L. J. , GEOR R. J. , HARE M. JESSIE , ECKER GAYLE L. , LINDINGER M. I. 
Published: June 2010

SummaryThe objective of this study was to determine the composition and extent of sweat losses during submaximal exercise under hot and humid conditions and to compare these findings with the same exercise protocol conducted under cool, dry and hot, dry conditions. Five Thoroughbred horses (age 3 to 6) completed exercise tests under each of 3 environmental conditions in random order: cool, dry (CD), room temperature (T) = 20°C, relative humidity (RH) = 45–55%; hot, dry (HD), T=32–34°C, RH=45–55%; and hot, humid (HH), T=32–34°C, RH=80–85%. Horses exercised at 50% of their predetermined V̇O2maxon a treadmill set at a 10% slope until attainment of a pulmonary artery blood temperature of 41.5°C followed by a 60 min recovery. Sweat was collected from a sealed polyethylene pouch enclosing a 150 cm2area on the lateral thorax. During exercise and the first 30 min of recovery, sweat fluid losses were 7.9 ± 0.7 litres, 9.9 ± 0.5 litres and 6.6 ± 1.2 litres (mean ± s.e.m.) for CD, HD and HH, respectively. Sweating rate (SR), calculated from sweat volume per unit area of enclosed skin, was lowest in CD and similar in HD and HH during exercise such that at end of exercise in HH (16.5 min) calculated sweat losses were approximately 5% and 32% higher than in HD and CD, respectively. In recovery, SR declined in all conditions but was significantly lower in CD (P<0.05). Sweating was detectable until 30 min recovery in CD, 45 min recovery in HD and 60 min recovery in HH. Sweat composition and osmolality was different under the 3 environmental conditions and changed gradually during exercise and recovery in all conditions. Osmolality and [Na] was highest in HD and lowest in CD. During exercise, [Na] increased with increasing SR. Although exercise duration was significantly decreased in HH (16.5 ± 1 min) when compared to HD (28 ± 2 min) and CD (37 ± 2 min), fluid and ion losses in HH were comparable to those in HD as a result of a high SR and prolonged sweating during recovery.
Redistribution of cardiac output in response to heat exposure in the pony
Authors: McCONAGHY FINOLA F. , HODGSON D. R. , ROSE R. J. , HALES J. R. S. 
Published: June 2010

SummaryRadioactive microspheres were used to measure cardiac output and blood flow to most major tissues in 4 ponies at rest in thermoneutral (16°C/60% RH) and mildly hot (41°C/34% RH) environments. In response to heat stress there were increases in cardiac output (2‐fold), respiratory frequency (5‐fold), blood flow to the skin of the body (3‐fold), and limbs (50%), respiratory muscles (2‐fold) and the upper respiratory tract (3‐fold). Ponies were able to maintain body temperature in the hot environment by increasing blood flow to the tissues involved in heat dissipation, while blood flow to all other tissues remained stable. This was achieved by increasing the cardiac output without need for reduction of blood flow to other tissues.
Modified ventilated capsule for the measurement of sweating rate in the exercising horse
Authors: SCOTT C. M. , MARLIN D. J. , SCHROTER R. C. 
Published: June 2010

SummaryModification of a ventilated capsule technique for the measurement of sweating rate (SR) is described for application in an exercising horse. The plastic capsule was sealed against the coat of the horse. Dry air was blown through the capsule over the skin and the change in absolute humidity (g/m3) between air entering and leaving the capsule was used to calculate SR. The effect of flow rate on the response characteristics of the system was investigated and measured over a range of sweating rates in a group of horses completing a short exercise test. Repeatability of SR measurements made at 2 sites, one 10 cm distal to thetuber sacrale(SRS) and the other approximately overlying C4 in the neck (SRN), were compared.To encourage the rapid and complete evaporation of moisture from the area of coat enclosed by the SR capsule, it was demonstrated that the degree of saturation of the air leaving the capsule should be maintained below 15% relative humidity (RH). This was best achieved at flow rates exceeding 35 l/min. No significant difference was found between the 2 repeated tests separated by 3 days, with respect to right atrial temperature (TRA) and SR. The modified system for the measurement of SR in the exercising horse used in this study was shown to be fast responding and capable of measuring a wide range of sweating rates. A good seal was maintained throughout and the capsule was removed without causing damage to the coat.
Sweat fluid and ion losses in horses during training and competition in cool vs. hot ambient conditions: implications for ion supplementation
Authors: McCUTCHEON L. J. , GEOR R. J. 
Published: June 2010

SummaryThe objectives of this study were to: 1) determine incremental and total sweat fluid and ion losses during and following (a) exercise training and (b) a treadmill Speed and Endurance exercise test (SEET) which simulated running speeds and distances required for each phase of an Olympic level (CCI****) 3‐day‐event in cool and hot ambient conditions and 2) determine the requirement for ion supplementation based on the calculated ion losses associated with these activities. Six exercise‐trained Thoroughbred horses completed 2 weeks of exercise training in each of 2 ambient conditions: cool, dry (CD, room temperature [T] = 20–22°C, relative humidity [RH] = 45–55%), or hot and humid (HH, T = 33–35°C, RH = 80–85%). Following the 2 week period of training in either CD or HH conditions, horses completed a SEET under similar conditions (either CD, or hot and dry (HD, T = 33–35°C, RH = 45–55%). Sweating rate and sweat ion composition for each 5 min interval was determined from sweat samples collected from a sealed pouch attached to the lateral thorax. Total sweat fluid losses during training in the heat were 2‐ or 3‐fold greater when compared to CD. Similarly, sweat fluid losses associated with the SEET in HD were almost double (19.2 litres) the losses in CD (11.7 litres). Total calculated ion losses associated with 2 h of training in HH (3724 mmol; 115.2 g) were significantly greater when compared to CD (1413 mmol; 43.5 g). Following the SEET and a 30 min recovery period, total ion losses in CD were 3636 mmol (112.2 g) compared with 6519 mmol (200.6 g) in HD. The differences in ion losses represent the increased sweating rates stimulated by higher core temperatures during moderate to high intensity exercise in warmer ambient conditions and increases in sweat ion concentrations associated with higher sweating rates. Extracellular fluid (ECF) ion losses during daily exercise training and the SEET were also calculated from changes in plasma ion concentrations and ECF volume. Calculated ECF ion losses were significantly higher in hot ambient conditions but were approximately 50% less than calculated sweat ion losses. The calculated sweat ion losses incurred during daily exercise training in hot and humid ambient conditions are >3‐fold higher than losses measured following exercise training in cooler conditions. Whereas fluid regulating hormones may have reduced urinary and faecal losses of ions during 2 weeks of training in HH, the quantity of sodium, potassium and chloride calculated to have been lost in sweat during the SEET in HD exceeded the daily dietary intake of these ions and suggests the need for appropriate ion supplementation during training and competition in hot ambient conditions.