Improved running performance in hot humid conditions following whole body precooling.

On two separate occasions, eight subjects controlled speed to run the greatest distance possible in 30 min in a hot, humid environment (ambient temperature 32 degrees C, relative humidity 60%). For the experimental test (precooling), exercise was preceeded by cold-water immersion. Precooling increased the distance run by 304 +/- 166 m (P < 0.05). Precooling decreased the pre-exercise rectal and mean skin temperature by 0.7 degrees C and 5.9 degrees C, respectively (P < 0.05). Rectal and mean skin temperature were decreased up to 20 and 25 min during exercise, respectively (P < 0.05). Mean body temperature decreased from 36.5 +/- 0.1 degrees C to 33.8 +/- 0.2 degrees C following precooling (P < 0.05) and remained lower throughout exercise (P < 0.01) and at the end of exercise (by 0.8 degrees C; P < 0.05). The rate of heat storage at the end of exercise increased from 113 +/- 45 to 249 +/- 55 W.m-2 (P < 0.005). Precooling lowered the heart rate at rest (13%), 5 (9%), and 10 min (10%) exercise (P < 0.05) and increased the end of exercise blood lactate from 4.9 +/- 0.5 to 7.4 +/- 0.9 mmol.L-1 (P < 0.01). The VO2 at 10 and 20 min of exercise and total body sweating are not different between tests. In conclusion, water immersion precooling increased exercise endurance in hot, humid conditions with an enhanced rate of heat storage and decreased thermoregulatory strain.

[1]  D. D. Bois,et al.  CLINICAL CALORIMETRY: TENTH PAPER A FORMULA TO ESTIMATE THE APPROXIMATE SURFACE AREA IF HEIGHT AND WEIGHT BE KNOWN , 1916 .

[2]  A. C. Burton,et al.  Human CalorimetryII. The Average Temperature of the Tissues of the Body: Three Figures , 1935 .

[3]  N. B. Strydom,et al.  Circulatory and metabolic reactions to work in heat. , 1962, Journal of applied physiology.

[4]  N. Ramanathan,et al.  A NEW WEIGHTING SYSTEM FOR MEAN SURFACE TEMPERATURE OF THE HUMAN BODY. , 1964, Journal of applied physiology.

[5]  B. Saltin,et al.  Esophageal, rectal, and muscle temperature during exercise. , 1966, Journal of applied physiology.

[6]  R A Bruce,et al.  Reductions in cardiac output, central blood volume, and stroke volume with thermal stress in normal men during exercise. , 1966, The Journal of clinical investigation.

[7]  B. Saltin,et al.  Body temperatures and sweating during exhaustive exercise. , 1972, Journal of applied physiology.

[8]  I Holmér,et al.  Metabolic and thermal response to swimming in water at varying temperatures. , 1974, Journal of applied physiology.

[9]  J A Dempsey,et al.  Effects of metabolic hyperthermia on performance during heavy prolonged exercise. , 1974, Journal of applied physiology.

[10]  W. C. Adams,et al.  Thermoregulation during marathon running in cool, moderate, and hot environments. , 1975, Journal of applied physiology.

[11]  E R Nadel,et al.  Circulatory regulation during exercise in different ambient temperatures. , 1979, Journal of applied physiology: respiratory, environmental and exercise physiology.

[12]  B. Ekblom,et al.  Physical performance and peak aerobic power at different body temperatures. , 1979, Journal of applied physiology: respiratory, environmental and exercise physiology.

[13]  K. Brück,et al.  Effect of a precooling maneuver on body temperature and exercise performance. , 1981, Journal of applied physiology: respiratory, environmental and exercise physiology.

[14]  G. Borg Psychophysical bases of perceived exertion. , 1982, Medicine and science in sports and exercise.

[15]  V. Hessemer,et al.  Effect of slightly lowered body temperatures on endurance performance in humans. , 1984, Journal of applied physiology: respiratory, environmental and exercise physiology.

[16]  J. Greenleaf,et al.  Hypothalamic, rectal, and muscle temperatures in exercising dogs: effect of cooling , 1985 .

[17]  J. Greenleaf,et al.  Exercise hyperthermia as a factor limiting physical performance: temperature effect on muscle metabolism. , 1985, Journal of applied physiology.

[18]  P. Webb Afterdrop of body temperature during rewarming: an alternative explanation. , 1986, Journal of applied physiology.

[19]  T T Romet,et al.  Mechanism of afterdrop after cold water immersion. , 1988, Journal of applied physiology.

[20]  K. Brück,et al.  Thermoregulatory, cardiovascular, and muscular factors related to exercise after precooling. , 1988, Journal of applied physiology.

[21]  I. Jacobs,et al.  Muscle glycogen utilization during shivering thermogenesis in humans. , 1988, Journal of applied physiology.

[22]  I. Jacobs,et al.  Muscle glycogen availability and temperature regulation in humans. , 1989, Journal of applied physiology.

[23]  W. L. Kenney,et al.  Control of skin blood flow during exercise. , 1992, Medicine and science in sports and exercise.

[24]  M. Febbraio,et al.  Muscle metabolism during exercise and heat stress in trained men: effect of acclimation. , 1994, Journal of applied physiology.

[25]  T M McLellan,et al.  Variability of time to exhaustion during submaximal exercise. , 1995, Canadian journal of applied physiology = Revue canadienne de physiologie appliquee.

[26]  D. T. Lee,et al.  Exercise duration and thermoregulatory responses after whole body precooling. , 1995, Journal of applied physiology.

[27]  A Jeukendrup,et al.  A new validated endurance performance test. , 1996, Medicine and science in sports and exercise.

[28]  B. Nielsen Olympics in Atlanta: a fight against physics. , 1996, Medicine and science in sports and exercise.