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:
doi: 10.1249/01.mss.0000218134.74238.6a
CLINICAL SCIENCES: Clinically Relevant
Abstract

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.

Author Information

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