Monitoring body temperature during moderate intensity exercise and inactive recovery in the cold

Abstract

Exposure to cold ambient conditions during outdoor recreation can lead to significant heat loss. It is unknown how fast body temperature decreases or how fast a person could become hypothermic in cold temperatures. We present a series of pilot tests involving moderate intensity exercise and inactive recovery in the cold to monitor how body temperature changes with exposure to -10°C. The primary aim of this pilot study was to test the feasibility of the proposed protocol with the intention to design a main study. The primary questions were: (i) to what degree does body temperature increase or decrease with this protocol, (ii) whether epitympanic temperature is a suitable measure of core temperature using a recently developed, non-invasive device and (iii) if participants are able to tolerate the cold during inactive recovery. This pilot series included seven participants. After an acclimatization phase (15 minutes), participants exercised at 60% peak heart rate (20 minutes) followed by a seated, inactive recovery phase (15 minutes) in the cold. The mean ambient conditions were -10.0±0.4°C and 66.1±8.6% relative humidity and no wind. The primary findings based on the feasibility criteria were that body temperature increased while exercising at an intensity of 60% HRpeak and decreased during inactive recovery by -0.3±0.1°C (epitympanic temperature). Secondly, the agreement between epitympanic and esophageal temperature (mean difference 0.2°C, 95% confidence interval -0.5 to 0.0, p=0.095) was better than in previous studies. Finally, all participants were able to tolerate the cold and complete the study despite thermal discomfort and shivering in the recovery phase. This protocol was successful in showing small changes in body temperature during exercise and recovery in the cold, though some modifications to the current protocol are recommended to elicit a larger effect size.

Keywords

• hypothermia
• core body temperature
• epitympanic temperature
• cooling rate
• cold exposure
• outdoor recreation