Constructing A Makeshift Heat Chamber Suitable For Thermoregulatory Research And Heat Acclimation Training

Environmental chambers (HEC) are crucial for thermoregulation and heat acclimation research, but cost burdens drive the creation of cost-effective makeshift heat chambers (MHC). While MHC’s offer affordability, doubts persist about a MHC's ability to maintain stable TEMP and %RH, potentially confounding physiological responses in human thermoregulation. PURPOSE: Build a MHC to maintain temperature and humidity suitable (±1.1-1.7 °C and ± 2-3 %) for thermoregulatory research and heat acclimation protocols. METHODS: A 10’x10’x8’ PVC frame with plastic sheeting, and 5 heaters and 3 humidifiers, was set to maintain 40 °C and 40% RH. 6 young adults, across BMI categories, underwent 4 exercise protocols (Resting, V̇O2max, Cycling, Heat Tolerance) in the MHC, recording TEMP and %RH every 3 minutes. The V̇O2max, cycling, and heat tolerance protocols were repeated for repeatability analysis. The heat tolerance protocol was performed a third time in a HEC for comparison. Descriptive statistics analyzed deviations from hypothetical means of 40 °C and 40%, while approximate F-tests and 95% confidence intervals assessed COV differences between trials and MHC-HEC. A linear mixed model explored factors (metabolic heat, outside temperature, equipment heat, BMI) affecting the deviation from the hypothetical mean TEMP (40 °C). Correlation analyses investigated links between independent factors and TEMP/%RH variations. RESULTS: Mean TEMP was consistently below the hypothetical 40 °C (39.90 ± 0.32 °C), while %RH was consistently higher than 40% (40.86 ± 0.59). TEMP COV range was 1.56-1.77%, and %RH COV was 4.66-5.62%. Repeated trials showed no differences in TEMP, %RH, and COV (95% CI, TEMP [39.81-39.98], %RH [40.44-41.15]; all p > 0.05). In heat tolerance, MHC displayed different TEMP (39.86-40.03 °C) and %RH (40.63-41.15%) compared to HEC (39.39-39.57 °C; 42.48-43.01%; p < 0.001). However, the MHC was closer to the hypothetical 40 °C and 40% than the HEC. The linear mixed model revealed no significant influence of factors on TEMP variation (All R2 < 0.50; p > 0.05). Correlation analyses showed weak non-significant correlations between independent factors and TEMP/%RH variations (r = -0.16-0.13; all p > 0.05). CONCLUSION: The constructed MHC, priced under $2,000, is suitable for thermoregulation research at 40 °C and 40% RH. Wyoming SBIR Phase 0 Funding and University of Washington ITHS Funding