Heat Strain and Gross Efficiency During Endurance Exercise after Lower, Upper, or Whole Body Precooling in the Heat

Abstract

The maximal power that muscles can generate is reduced at low muscle temperatures. However, in prolonged heavy exercise in the heat, a high core temperature may be the factor limiting performance. Precooling has been shown to delay the attainment of hyperthermia. It is still unclear if the whole body should be cooled or if the active muscles should be excluded from cooling in order to maintain muscle power. An experiment was performed to compare thermal strain and gross efficiency following whole body or partial body cooling. Eight well-trained participants performed 40 min of 60 % V·O_2max cycling exercise in a 30 °C, 70 % relative humidity climatic chamber after four different precooling sessions in a water perfused suit: N (no precooling), CC (45 min whole body precooling), WC (45 min lower body precooling), and CW (45 min upper body precooling). The uncooled body part was warmed in such a way that the core temperature did not differ from that in session N. Gross efficiency was used to compare performance between the sessions since it indicates how much oxygen is needed for a certain external load. The gross efficiency did not differ significantly between the sessions. Differences in heat loss and heat storage were observed during the first 20 min of exercise. The evaporative heat loss in session WC (305 ± 67 W) and CW (284 ± 68 W) differed from session N (398 ± 77 W) and CC (209 ± 58 W). More heat was stored in session CC (442 ± 125 W) than in sessions WC (316 ± 39 W), CW (307 ± 63 W), and N (221 ± 65 W). It was confirmed that precooling reduces heat strain during exercise in the heat. No differences in heat strain and gross efficiency were observed between precooling of the body part with the exercising muscles and precooling of the tissues elsewhere in the body.

Heat balance - heat exhaustion - cycling

References

• 1 Arngrímsson A A, Petitt D S, Stueck M G, Jorgensen D K, Cureton K J. Cooling vest worn during active warm-up improves 5-km run performance in the heat.  J Appl Physiol. 2004;  96 1867-1874
• 2 Asmussen E, Böje O. Body temperature and capacity for work.  Acta Physiol Scand. 1945;  10 1-22
• 3 Beelen A, Sargeant A J. Effect of lowered muscle temperature on the physiological response to exercise in men.  Eur J Appl Physiol. 1991;  63 387-392
• 4 Bennett A F. Thermal dependence of muscle function.  Am J Physiol. 1984;  247 217-229
• 5 Bolster D R, Trappe S W, Short K R, Scheffield-Moore M, Parcell A C, Schulze K M, Costill D L. Effects of precooling on thermoregulation during subsequent exercise.  Med Sci Sports Exerc. 1999;  31 251-257
• 6 Booth J, Marino F E, Ward J J. Improved running performance in hot humid conditions following whole body precooling.  Med Sci Sports Exerc. 1997;  29 943-949
• 7 Borg G AV. Psychophysical bases of physical exertion.  Med Sci Sports Exerc. 1982;  14 377-381
• 8 Brück K, Olschewski H. Body temperature related factors diminishing the drive to exercise.  Can J Physiol Pharmacol. 1987;  65 1274-1280
• 9 Burton A. Human calorimetry II. The average temperature of the tissues of the body.  J Nutr. 1935;  9 261-280
• 10 Cotter J D, Sleivert G G, Roberts W S, Febbraio M A. Effect of pre-cooling, with and without thigh cooling, on strain and endurance exercise performance in the heat.  Comp Biochem Physiol A. 2001;  128 667-677
• 11 Davies C TM, Mecrow I K, White M J. Contractile properties of the human triceps surae with some observations on the effects of temperature and exercise.  Eur J Appl Physiol. 1982;  49 255-269
• 12 DuBois D, DuBois E F. A formula to estimate the appropriate surface area if height and weight be known.  Arch Intern Med. 1916;  17 863-871
• 13 Fanger P O. Thermal Comfort. New York; McGraw-Hill Book Co 1970
• 14 Febbraio M A. Does muscle function and metabolism affect exercise performance in the heat?.  Exerc Sport Sci Rev. 2000;  28 171-176
• 15 Garby L, Astrup A. The relationship between the respiratory quotient and the energy equivalent of oxygen during simultaneous glucose and lipid oxidation and lipogenesis.  Acta Physiol Scand. 1987;  129 443-444
• 16 Giesbrecht G G, Bristow G K. The convective afterdrop component during hypothermic exercise decreases with delayed exercise onset.  Aviat Space Environ Med. 1998;  69 17-22
• 17 Gisolfi C V, Mora F. The Hot Brain: Survival, Temperature, and the Human Body. Cambridge, Massachusetts London, England; The MIT Press 2000
• 18 Givoni B, Goldman R F. Predicting rectal temperature response to work, environment, and clothing.  J Appl Physiol. 1972;  32 812-822
• 19 González-Alonso J, Teller C, Andersen S L, Jensen F B, Hyldig T, Nielsen B. Influence of body temperature on the development of fatigue during prolonged exercise in the heat.  J Appl Physiol. 1999;  86 1032-1039
• 20 Havenith G, Luttikholt V GM, Vrijkotte T GM. The relative influence of body characteristics on humid heat stress response.  Eur J Appl Physiol. 1995;  70 270-279
• 21 Havenith G, Heus R, Lotens W A. Resultant clothing insulation: a function of body movement, posture, wind, clothing fit, and ensemble thickness.  Ergonomics. 1990;  33 67-84
• 22 Hessemer V, Lagusch D, Bruck L K, Bodeker R H, Breidenbach T. Effect of slightly lowered body temperatures on endurance performance in humans.  J Appl Physiol. 1984;  57 1731-1737
• 23 Hill A V. Living Machinery. New York; Harcourt, Brace & World, Inc. 1927
• 24 Houdas Y, Ring E FJ. Human Body Temperature. New York; Plenum Press 1982
• 25 Hunter J, Kerr E H, Whillans M G. The relation between joint stiffness upon exposure to cold and the characteristics of synovial fluid.  Can J Med Sci. 1952;  30 367-377
• 26 Ingen Schenau van G J, Cavanagh P R. Power equations in endurance sports.  J Biomech. 1990;  23 865-881
• 27 ISO 9886. Evaluation of Thermal Strain by Physiological Measurements. Geneva; ISO 2000
• 28 ISO 10 551. Ergonomics of the Thermal Environment - Assessment of the Influence of the Thermal Environment Using Subjective Judgement Scales. Geneva; ISO 1993
• 29 Kenny G P, Reardon F D, Zeleski W, Reardon M L, Haman F, Ducharme M B. Muscle temperature transients before, during, and after exercise measured using an intramuscular multisensor probe.  J Appl Physiol. 2003;  94 2350-2357
• 30 Kerslake D MCK. The Stress of Hot Environments. Cambridge, UK; Cambridge University Press 1972
• 31 Lee D T, Haymes E M. Exercise duration and thermoregulatory responses after whole body precooling.  J Appl Physiol. 1995;  79 1971-1976
• 32 Lotens W A. Heat Transfer from Wearing Clothing. PhD Thesis. Soesterberg, NL; TNO Human Factors 1993
• 33 Lucia A, San Juan A F, Montilla M, CaNete S, Santalla A, Earnest C, Pérez M. In professional road cyclists, low pedalling cadences are less efficient.  Med Sci Sports Exerc. 2004;  36 1048-1054
• 34 Marino F E. Methods, advantages, and limitations of body cooling for exercise performance.  Br J Sports Med. 2002;  36 89-94
• 35 Maughan R J. Exercise in the heat: limitations to performance and the impact of fluid replacement strategies.  Can J Appl Physiol. 1999;  24 149-151
• 36 Mittal B B, Sathiaseelan V, Rademaker A W, Pierce M C, Johnson P M, Brand W N. Evaluation of an ingestible telemetric temperature sensor for deep hyperthermia applications.  Int J Radiat Onc Biol Physics. 1991;  21 1353-1361
• 37 Nielsen M. Die Regulation der Körpertemperatur bei Muskelarbeit.  Skand Arch Physiol. 1938;  79 193-230
• 38 Nielsen B. Heat stress and acclimation.  Ergonomics. 1994;  37 49-58
• 39 Nielsen B, Hales J RS, Strange S, Christensen N J, Warberg J, Saltin B. Human circulatory and thermoregulatory adaptations with heat acclimation and exercise in a hot, dry environment.  J Physiol. 1993;  460 467-485
• 40 Nielsen B, Hyldig T, Bidstrup F, González-Alonso J, Christoffersen G RJ. Brain activity and fatigue during prolonged exercise in the heat.  Eur J Physiol. 2001;  442 41-48
• 41 Nybo L, Nielsen B. Hyperthermia and central fatigue during prolonged exercise in humans.  J Appl Physiol. 2001;  91 1055-1060
• 42 Olschewski H, Brück K. Thermoregulatory, cardiovascular and muscular factors related to exercise after precooling.  J Appl Physiol. 1988;  64 803-811
• 43 Price M J, Mather M I. Comparison of lower- vs. upper-body cooling during arm exercise in hot conditions.  Aviat Space Environ Med. 2004;  75 220-226
• 44 Schmidt V, Brück K. Effect of a precooling maneuver on body temperature and exercise performance.  J Appl Physiol. 1981;  50 772-778
• 45 Smith J A, Yates K, Lee H, Thompson M W, Holcombe B V, Martin D T. Precooling improves cycling in hot/humid conditions.  Med Sci Sports Exerc. 1997;  29 263 (abstract)
• 46 Sparling P B, Snow T L, Millard-Stafford M L. Monitoring core temperature during exercise: ingestible sensor vs. rectal thermistor.  Aviat Space Environ Med. 1993;  64 760-763