Continuous thermoregulatory responses to mass-participation distance running in heat

• Published in: Medicine and science in sports and exercise 2006-05, Vol.38 (5), p.803-810
• Main Authors: BYRNE, Christopher, KAI WEI LEE, Jason, AI NEO CHEW, Serena, CHIN LEONG LIM, YU MING TAN, Elaine
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Body Temperature Regulation - physiology; Dehydration; Fundamental and applied biological sciences. Psychology; Heart Rate; Hot Temperature; Humans; Humidity; Male; Monitoring, Physiologic - instrumentation; Running - physiology; Singapore; Space life sciences; Vertebrates: body movement. Posture. Locomotion. Flight. Swimming. Physical exercise. Rest. Sports; Water-Electrolyte Balance - physiology
• ISSN: 0195-9131; 1530-0315
• DOI: 10.1249/01.mss.0000218134.74238.6a

To continuously measure core temperature (T(c)) and heart rate(HR), and quantify fluid balance during a 21-km mass-participation road racein warm, humid environmental conditions. Eighteen heat-acclimatized male soldiers ingested a telemetric Tc sensor on the evening prior to the race and wore an ambulatory T(c) data recorder and HR monitor during the race. Pre- to postrace changes in nude body mass quantified fluid balance. Environmental wet bulb globe temperature averaged 26.5 degrees C. All runners finished the race asymptomatic of heat illness in a mean +/- SD (range) time of 118 +/- 13 (105-146) min, corresponding to an average running speed of 10.8 +/- 1.1 (8.6-12.0) km.h(-1). All runners recorded peak T(c) > 39 degrees C; 56% (N = 10) > 40 degrees C; and 11% (N = 2) > 41 degrees C. Peak T(c) was 40.1 +/- 0.7 (39.3-41.7) degrees C at 86 +/- 36 (13-130) min, with T(c) 39.9 +/- 0.8 (38.3-41.7) degrees C at race finish. The magnitude of T(c) response was unrelated (P > 0.05) to running time or fluid balance (e.g., fluid intake, % dehydration). Cumulative heat strain index was 2790 +/- 1112 (1046-5144) units at race finish. Ingestible telemetric temperature sensors demonstrated utility for continuous measurement of T(c) during mass-participation running. Successful application of this technology has highlighted the magnitude and duration of T(c) elevation that runners will voluntarily achieve during mass-participation distance races in heat and high humidity without medical consequence.