Sex-Related Differences in Dynamic Heat Balance: Metabolic Heat Production Considerations
Bibliographic record
Abstract
Sex-related differences in thermoregulatory responses during exercise in the heat have typically been attributed to anthropometric characteristics. After accounting for such characteristics, and when working at the same relative oxygen consumption (VO2), females have been shown to sweat less than males, while maintaining similar core temperatures. However, workloads based upon relative maximal VO2 do not take into consideration differences in rates of metabolic heat production (M-W). Therefore, we evaluated the hypothesis that sex-related differences in rates of evaporative heat loss (EHL) during exercise at the same relative VO2 are due to differences in M-W. PURPOSE: To determine if different rates of M-W elicited by workloads of the same percentage of maximal VO2 would result in proportional differences in EHL between sexes. METHODS: 8 males and 7 females cycled for 60-min at 40% VO2 in a hot dry environment (40°C, 30% RH) within the modified Snellen whole-body air calorimeter. Subjects were matched for body surface area to mass ratio and for maximal VO2 relative to lean body mass. EHL and dry heat gain (DHG), as well as changes in body heat content (ΔHb) were determined by direct calorimetry. M-W was concurrently measured using indirect calorimetry. Rectal temperature (Tre) was measured continuously. RESULTS: Throughout exercise, M-W was higher in males compared to females (209±26 vs 249±35 W·m−2, p=0.05). Consequently, rates of EHL (225±28 vs 253±37 W·m−2, p=0.05) were proportionally higher. This resulted in a greater ΔHb (306±71 vs 455±127 KJ, p=0.05). This body heat storage resulted in a larger rise from baseline in Tre (0.82±0.20 vs 1.21±0.29°C, p=0.05) for males despite their greater total body mass and mean specific heat of body tissues. When accounting for differences in total heat load (M-W+ DHG) however, there were no differences in EHL between sexes (p>0.05). CONCLUSION: Despite working at the same percentage of VO2, the higher metabolic heat load in males throughout exercise resulted in a higher absolute EHL but also a greater ΔHb. Therefore, it is important to consider metabolic heat production when comparing possible thermoregulatory sex-related differences during exercise. Supported by Natural Sciences and Engineering Research Council and US Army Medical Research Acquisition Activity Grants.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.005 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".