Does Body Surface Area Independently Alter Whole‐body Sweat Loss during Exercise at a Fixed Absolute Evaporative Requirement for Heat Balance?
Bibliographic record
Abstract
The absolute evaporative requirement for heat balance (E req ) is the principal determinant of whole‐body sweat loss (WBSL) during fixed‐duration exercise in ambient conditions that permit complete sweat evaporation, regardless of body size. However, exercise at a fixed absolute E req in hot/humid conditions may lead to disproportionately greater WBSL among individuals of smaller body surface area (BSA) due to a lower absolute maximum evaporative capacity and thus higher skin wettedness required for heat balance (ω req ) and lower sweating efficiency (S eff ). To test this hypothesis, young adult males of small (SM: 1.81±0.07 m 2 ; n=4) or large (LG: 2.28±0.15 m 2 ; n=3) BSA cycled for 70 min at 34±0.3°C, 71.8±1.3% RH at an exercise intensity set to elicit a fixed VO 2 of 1.5 L/min, and therefore a metabolic heat production of ~450 W and an E req of ~430 W (indirect calorimetry). Body mass was measured at 0, 45, and 70 min to estimate WBSL during non‐steady‐state (0–45 min) and steady‐state (45–70 min) exercise. S eff was calculated as the quotient of the WBSL required to attain E req with complete evaporation and the observed WBSL during the steady‐state period, and expressed as a percentage. The attainment of a steady state (i.e., the actual rate of evaporation equaled the required rate of evaporation) from 45 to 70 min was confirmed by stable esophageal and skin temperatures (±0.1°C throughout steady state). During non‐steady‐state exercise, ω req was not different between groups (SM: 0.81±0.05 g; LG: 0.73±0.08 g; P=0.17), and no between‐group difference in WBSL was observed (SM: 522±81 g; LG: 476±115 g; P=0.56). In contrast, steady‐state ω req was greater in SM (SM: 0.81±0.03; LG: 0.71±0.04; P=0.02), leading to significantly higher WBSL (SM: 361±49 g; LG: 260±54 g; P<0.05) and diminished S eff (SM: 74.1±12.7%; LG: 96.3±6.4%; P=0.04) in the SM group. In summary, our preliminary data suggest that in hot/humid ambient conditions, a large between‐group difference in BSA may lead to disproportionately greater steady‐state WBSL in smaller individuals despite exercising at the same absolute E req due to an independent effect of BSA on S eff . Support or Funding Information Supported by an NSERC Discovery Grant (O. Jay)
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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 | 0.000 | 0.000 |
| 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) | 0.002 | 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".