Abstract
BackgroundDeep body temperature is a critical indicator of heat strain. However, direct measures are often invasive, costly, and difficult to implement in the field. This study assessed the agreement between deep body temperature estimated from heart rate and that measured directly during repeated work bouts while wearing explosive ordnance disposal (EOD) protective clothing and during recovery.MethodsEight males completed three work and recovery periods across two separate days. Work consisted of treadmill walking on a 1% incline at 2.5, 4.0, or 5.5 km/h, in a random order, wearing EOD protective clothing. Ambient temperature and relative humidity were maintained at 24 °C and 50% [Wet bulb globe temperature (WBGT) (20.9 ± 1.2) °C] or 32 °C and 60% [WBGT (29.0 ± 0.2) °C] on the separate days, respectively. Heart rate and gastrointestinal temperature (TGI) were monitored continuously, and deep body temperature was also estimated from heart rate (ECTemp).ResultsThe overall systematic bias between TGI and ECTemp was 0.01 °C with 95% limits of agreement (LoA) of ±0.64 °C and a root mean square error of 0.32 °C. The average error statistics among participants showed no significant differences in error between the exercise and recovery periods or the environmental conditions. At TGI levels of (37.0–37.5) °C, (37.5–38.0) °C, (38.0–38.5) °C, and > 38.5 °C, the systematic bias and ± 95% LoA were (0.08 ± 0.58) °C, (− 0.02 ± 0.69) °C, (− 0.07 ± 0.63) °C, and (− 0.32 ± 0.56) °C, respectively.ConclusionsThe findings demonstrate acceptable validity of the ECTemp up to 38.5 °C. Conducting work within an ECTemp limit of 38.4 °C, in conditions similar to the present study, would protect the majority of personnel from an excessive elevation in deep body temperature (> 39.0 °C).
Highlights
Deep body temperature is a critical indicator of heat strain
This study aimed to assess the agreement between deep body temperature estimated from heart rate (ECTemp) and that measured directly during repeated work bouts wearing explosive ordnance disposal (EOD) protective clothing and during recovery periods
The observed level of agreement was within the criteria set for monitoring deep body temperature in a field setting and was in accordance with the assumptions underpinning current occupational guidelines
Summary
Deep body temperature is a critical indicator of heat strain. direct measures are often invasive, costly, and difficult to implement in the field. Clothing worn by technicians during explosive ordnance disposal (EOD) is vital for protecting the wearer from ballistic threats during their work The barrier it creates between the wearer and the environment, as well as the weight and bulk of the clothing, both impair body heat loss [1, 2] and increase metabolic rate [3], leading to a warmer deep body temperature. Temperature variations along the gastrointestinal tract [13] and those resulting from food and fluid ingestion [18] can obscure a true deep body temperature reading at a given time Aside from these invasive measurement techniques, a range of noninvasive measurement devices are available as surrogate measures of deep body temperature. There are continued research efforts to develop a measure of deep body temperature that is both valid, field expedient, and noninvasive
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