Prolonged Work in the Heat Impairs Heat Loss on the Next day in Older Men
Bibliographic record
Abstract
Performing prolonged, arduous occupational work in the heat is associated with considerable heat strain, which may be exacerbated on the next work day. Recently, we showed that whole-body heat loss was not modified by prolonged work in the heat on the preceding day in young habitually active men. However, it is unclear whether prolonged heat strain may reduce heat loss on the next day in older workers, who display impaired thermoregulatory function and who recover more slowly from exercise-induced stress compared to young adults. PURPOSE: To determine whether prolonged work in the heat impairs whole-body heat loss and exacerbates heat storage on the next day in older men. METHODS: Changes in whole-body heat exchange and heat storage were assessed in six older (60 years (SD 5)) men during heat stress tests performed on the same day prior to (Day 1), and on the day following (Day 2), a prolonged work simulation. Each heat stress test involved three, 30-min bouts of cycling performed at increasing, fixed rates of metabolic heat production of 150 (Ex1), 200 (Ex2) and 250 W/m2 (Ex3), each separated by 15-min recovery, in hot-dry conditions (40°C, 20% relative humidity (RH)). The work simulation (7.5 h) involved three moderate intensity intermittent work bouts (2 h) each separated by 30-min rest breaks in hot-dry conditions (38°C, 34% RH). Total heat loss (evaporative ± dry heat exchange) and metabolic heat production were measured using direct and indirect calorimetry, respectively. Body heat storage was quantified as the temporal summation of heat production and loss. RESULTS: Total heat loss (mean±95% CI) during Ex1 did not differ between Day 1 (149±8 W/m2) and Day 2 (143±6 W/m2; P=0.29), but decreased on Day 2 during Ex2 (181±7 W/m2) and Ex3 (219±10 W/m2) relative to Day 1 (191±7 and 230±14 W/m2, respectively; both P<0.01). As a result, body heat storage across all exercise bouts was 19% greater on Day 2 (364±74 kJ) than on Day 1 (295±50 kJ; P=0.02). CONCLUSIONS: Prolonged work in the heat impairs whole-body heat loss and exacerbates body heat storage during moderate-to-high intensity work on the next day in older men. These outcomes indicate that older workers may be more vulnerable to heat-related illness when performing consecutive, arduous work shifts. Supported by the Natural Sciences and Engineering Research Council of Canada.
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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) | 0.001 | 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".