Age-related differences in heat loss capacity occur under both dry and humid heat stress conditions
Bibliographic record
Abstract
This study examined the progression of impairments in heat dissipation as a function of age and environmental conditions. Sixty men (n = 12 per group; 20-30, 40-44, 45-49, 50-54, and 55-70 yr) performed four intermittent exercise/recovery cycles for a duration of 2 h in dry (35°C, 20% relative humidity) and humid (35°C, 60% relative humidity) conditions. Evaporative heat loss and metabolic heat production were measured by direct and indirect calorimetry, respectively. Body heat storage was measured as the temporal summation of heat production and heat loss during the sessions. Evaporative heat loss was reduced during exercise in the humid vs. dry condition in age groups 20-30 (-17%), 40-44 (-18%), 45-49 (-21%), 50-54 (-25%), and 55-70 yr (-20%). HE fell short of being significantly different between groups in the dry condition, but was greater in age group 20-30 yr (279 ± 10 W) compared with age groups 45-49 (248 ± 8 W), 50-54 (242 ± 6 W), and 55-70 yr (240 ± 7 W) in the humid condition. As a result of a reduced rate of heat dissipation predominantly during exercise, age groups 40-70 yr stored between 60-85 and 13-38% more heat than age group 20-30 yr in the dry and humid conditions, respectively. These age-related differences in heat dissipation and heat storage were not paralleled by significant differences in local sweating and skin blood flow, or by differences in core temperature between groups. From a whole body perspective, combined heat and humidity impeded heat dissipation to a similar extent across age groups, but, more importantly, intermittent exercise in dry and humid heat stress conditions created a greater thermoregulatory challenge for middle-aged and older adults.
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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 | 0.001 |
| 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) | 0.001 | 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".