Worker heat stress prevention and work metabolism estimation: comparing two assessment methods of the heart rate thermal component.

The heart rate thermal component ( ) can increase with body heat accumulation and lead to work metabolism (WM) overestimation. We used two methods (VOGT and KAMP) to assess of 35 forest workers throughout their work shifts, then compared at work and at rest using limits of agreement (LoA). Next, for a subsample of 20 forest workers, we produced corrected WM estimates from and compared them to measured WM. Although both methods produced significantly different time-related profiles, they yielded comparable average thermal cardiac reactivity (VOGT: 24.8 bpm °C; KAMP: 24.5 bpm °C), average (LoA: 0.7 ± 11.2 bpm) and average WM estimates (LoA: 0.2 ± 3.4 ml O kgmin for VOGT, and 0.0 ± 5.4 ml O kgmin for KAMP). Both methods are suitable to assess heat stress through and improve WM estimation. We compared two methods for assessing the heart rate thermal component ( ), which is needed to produce a corrected HR profile for estimating work metabolism (WM). Both methods yielded similar estimates that allowed accurate estimations of heat stress and WM at the group level, but they were imprecise at the individual level. AIC: akaike information criterion; bpm: beats per minute; CI: confidence intervals; CV: coefficient of variation in %; CV drift: cardiovascular drift; ΔHR: the heart rate thermal component in bpm; ΔHR: the heart rate thermal component in bpm; ΔΔHR: variation in the heart rate thermal component in bpm; ΔT: variation in core body temperature in °C; HR: heart rate in bpm; HRmax: maximal heart rate in bpm; Icl: cloting insulation in clo; KAMP: Kampmann et al. (2001) method to determe ΔHR; LoA: Limits of Agreement; PMV-PPD: the Predicted Mean Vote and Predicted Percentage Dissatisfied; PHS: Predicted Heat Strain model; RCM: random coefficients model; SD: standard deviation; TC: core body temperature in °C; TCR: thermal cardiac reactivity in bpm °C; τ: rate of change in the heart rate thermal component in bpm min; τ: rate of change in core body temperature in °C min; t: Student's t statistic with level of confidence alpha and n degrees of freedom; TWL: Thermal Work Limit model; : oxygen consumption in ml O kg min; max: maximal oxygen consumption in ml O kg min; VOGT: Vogt et al. (1973) method to determine ΔHR; WBGT: Wet-Bulb Globe Temperature in °C; WM: work metabolism.