Continuous Thermoregulatory Responses to Mass-Participation Distance Running in Heat

BYRNE, CHRISTOPHER; LEE, JASON KAI WEI; CHEW, SERENA AI NEO; LIM, CHIN LEONG; TAN, ELAINE YU MING

Medicine & Science in Sports & Exercise: May 2006 - Volume 38 - Issue 5 - pp 803-810
doi: 10.1249/01.mss.0000218134.74238.6a
CLINICAL SCIENCES: Clinically Relevant

Purpose: To continuously measure core temperature (Tc) and heart rate(HR), and quantify fluid balance during a 21-km mass-participation road racein warm, humid environmental conditions.

Methods: Eighteen heat-acclimatized male soldiers ingested a telemetric Tc sensor on the evening prior to the race and wore an ambulatory Tc data recorder and HR monitor during the race. Pre- to postrace changes in nude body mass quantified fluid balance.

Results: Environmental wet bulb globe temperature averaged 26.5°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 Tc > 39°C; 56% (N = 10) > 40°C; and 11% (N = 2) > 41°C. Peak Tc was 40.1 ± 0.7 (39.3-41.7) °C at 86 ± 36 (13-130) min, with Tc 39.9 ± 0.8 (38.3-41.7) °C at race finish. The magnitude of Tc 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.

Conclusion: Ingestible telemetric temperature sensors demonstrated utility for continuous measurement of Tc during mass-participation running. Successful application of this technology has highlighted the magnitude and durationof Tc elevation that runners will voluntarily achieve during mass-participation distance races in heat and high humidity without medical consequence.

Centre for Human Performance, Defence Medical and Environmental Research Institute, DSO National Laboratories, REPUBLIC OF SINGAPORE

Address for correspondence: Christopher Byrne, School of Life Sciences, Heriot-Watt University, Edinburgh, Scotland, United Kingdom, EH14 4AS; E-mail: C.Byrne@hw.ac.uk.

Submitted for publication March 2005.

Accepted for publication December 2005.

©2006The American College of Sports Medicine