Within-subject Variation of Thermoregulatory Responses during Repeated Exercise Bouts

Abstract

Aim: To assess the within-subject variation of thermoregulatory responses during 2 consecutive 15-km road races. Secondly, we explored whether gastrointestinal temperature (T_GI) data from the first race could improve our previously established predictive model for finish T_GI in the second race.

Methods: We measured T_GI before and immediately after both races in 58 participants and determined correlation coefficients. Finish T_GI in the second race was predicted using a linear regression analysis including age, BMI, pre-race fluid intake, T_GI increase between baseline and the start of the race and finish T_GI in the first race.

Results: Under cool conditions (WBGT 11–12°C), T_GI was comparable between both races at baseline (37.6±0.4°C vs. 37.9±0.4°C; p=0.24) and finish (39.4±0.6°C vs. 39.4±0.6°C; p=0.83). Finish T_GI correlated significantly between both races (r=0.50; p<0.001). The predictive model (p<0.001) could predict 32.2% of the finish TGI in the second race (vs. 17.1% without finish TGI in race 1).

Conclusion: Our findings demonstrate that the use of previously obtained thermoregulatory responses results in higher predictability of finish core body temperatures in future races, enabling better risk assessment for those athletes that are most likely to benefit from preventive measures.

Key word

heatstroke - heat stress disorders - body temperature regulation - body temperature - exercise physiology

• References

• 1 Armstrong LE, Casa DJ, Millard-Stafford M, Moran DS, Pyne SW, Roberts WO. American College of Sports Medicine position stand. Exertional heat illness during training and competition. Med Sci Sports Exerc 2007; 39: 556-572
• 2 Bedno SA, Li Y, Han W, Cowan DN, Scott CT, Cavicchia MA, Niebuhr DW. Exertional heat illness among overweight U.S. Army recruits in basic training. Aviat Space Environ Med 2010; 81: 107-111
• 3 Binkley HM, Beckett J, Casa DJ, Kleiner DM, Plummer PE. National Athletic Trainers’ Association Position Statement: Exertional Heat Illnesses. J Athl Train 2002; 37: 329-343
• 4 Bongers CC, Thijssen DH, Veltmeijer MT, Hopman MT, Eijsvogels TM. Precooling and percooling (cooling during exercise) both improve performance in the heat: a meta-analytical review. Br J Sports Med 2014;
• 5 Bradford CD, Cotter JD, Thorburn MS, Walker RJ, Gerrard DF. Exercise can be pyrogenic in humans. Am J Physiol 2007; 292: R143-149
• 6 Byrne C, Lim CL. The ingestible telemetric body core temperature sensor: a review of validity and exercise applications. Br J Sports Med 2007; 41: 126-133
• 7 Casa DJ, Armstrong LE, Kenny GP, O’Connor FG, Huggins RA. Exertional heat stroke: new concepts regarding cause and care. Curr Sports Med Rep 2012; 11: 115-123
• 8 Casa DJ, Clarkson PM, Roberts WO. American College of Sports Medicine roundtable on hydration and physical activity: consensus statements. Curr Sports Med Rep 2005; 4: 115-127
• 9 Cheuvront SN, Haymes EM. Thermoregulation and marathon running: biological and environmental influences. Sports Med 2001; 31: 743-762
• 10 Coris EE, Mehra S, Walz SM, Duncanson R, Jennings J, Nugent D, Zwygart K, Pescasio M. Gastrointestinal temperature trends in football linemen during physical exertion under heat stress. South Med J 2009; 102: 569-574
• 11 Daanen HA, Jonkman AG, Layden JD, Linnane DM, Weller AS. Optimising the acquisition and retention of heat acclimation. Int J Sports Med 2011; 32: 822-828
• 12 DuBois DDE. A formula to estimate the approximate surface area if height and weight are known. Arch Intern Med 1916; 17: 869-871
• 13 Ely BR, Ely MR, Cheuvront SN, Kenefick RW, Degroot DW, Montain SJ. Evidence against a 40 degrees C core temperature threshold for fatigue in humans. J Appl Physiol 2009; 107: 1519-1525
• 14 Gant N, Atkinson G, Williams C. The validity and reliability of intestinal temperature during intermittent running. Med Sci Sports Exerc 2006; 38: 1926-1931
• 15 Gonzalez-Alonso J, Quistorff B, Krustrup P, Bangsbo J, Saltin B. Heat production in human skeletal muscle at the onset of intense dynamic exercise. J Physiol 2000; 524 (Pt 2) 603-615
• 16 Harriss DJ, Atkinson G. Ethical standards in sport and exercise science research: 2014 update. Int J Sports Med 2013; 34: 1025-1028
• 17 Howe AS, Boden BP. Heat-related illness in athletes. Am J Sports Med 2007; 35: 1384-1395
• 18 Martin L, Doggart AL, Whyte GP. Comparison of physiological responses to morning and evening submaximal running. J Sports Sci 2001; 19: 969-976
• 19 Mauger AR, Taylor L, Harding C, Wright B, Foster J, Castle P. Acute acetaminophen (paracetamol) ingestion improves time to exhaustion during exercise in the heat. Exp Physiol 2013;
• 20 Maughan RJ, Leiper JB, Thompson J. Rectal temperature after marathon running. Br J Sports Med 1985; 19: 192-195
• 21 Noakes TD, Myburgh KH, du Plessis J, Lang L, Lambert M, van der Riet C, Schall R. Metabolic rate, not percent dehydration, predicts rectal temperature in marathon runners. Med Sci Sports Exerc 1991; 23: 443-449
• 22 Periard JD, Cramer MN, Chapman PG, Caillaud C, Thompson MW. Neuromuscular function following prolonged intense self-paced exercise in hot climatic conditions. Eur J Appl Physiol 2011; 111: 1561-1569
• 23 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: 377-390
• 24 Tucker R, Rauch L, Harley YX, Noakes TD. Impaired exercise performance in the heat is associated with an anticipatory reduction in skeletal muscle recruitment. Pflugers Arch 2004; 448: 422-430
• 25 Veltmeijer MT, Eijsvogels TM, Thijssen DH, Hopman MT. Incidence and predictors of exertional hyperthermia after a 15-km road race in cool environmental conditions. J Sci Med Sport. 2014
• 26 Wallace RF, Kriebel D, Punnett L, Wegman DH, Wenger CB, Gardner JW, Gonzalez RR. The effects of continuous hot weather training on risk of exertional heat illness. Med Sci Sports Exerc 2005; 37: 84-90
• 27 Wendt D, van Loon LJ, Lichtenbelt WD. Thermoregulation during exercise in the heat: strategies for maintaining health and performance. Sports Med 2007; 37: 669-682
• 28 Wilkinson DM, Carter JM, Richmond VL, Blacker SD, Rayson MP. The effect of cool water ingestion on gastrointestinal pill temperature. Med Sci Sports Exerc 2008; 40: 523-528