Short-Term Warm Water Immersion for Improving Whole-Body Heat Loss in Older Men
Bibliographic record
Abstract
PURPOSE: Exercise-induced heat acclimation can mitigate age-related reductions in heat loss capacity, although performing repeated bouts of strenuous exercise in the heat may be untenable for many older adults. Although short-term passive heat acclimation (e.g., ≤7 days of warm water immersion) enhances whole-body heat loss in young adults, evidence of its efficacy in older adults is lacking. Thus, we examined whether 7 days of warm water immersion would improve whole-body heat loss in older adults. METHODS: Twelve habitually active older men (median [interquartile-range] age, 68 [64-73] years; peak oxygen uptake (V̇O 2peak ), 34.1 [29.4-36.1] mL O 2 ·kg -1 ·min -1 ) completed 7 consecutive days of ~90-min warm water immersion (~40°C) with core (rectal) temperature clamped at ~38.5°C for the final 60 min. Before and after the warm water immersion intervention, whole-body total (evaporative + dry) heat loss was measured via direct calorimetry during three, 30-min bouts of cycling at increasing fixed rates of metabolic heat production (150, 200, and 250 W·m -2 ), each separated by 15-min rest, in a hot-dry environment (40°C, ~13% relative humidity). Rectal temperature and heart rate were measured continuously. RESULTS: Following 7 days of warm water immersion, whole-body total heat loss was elevated by 23 [95% confidence interval; 14, 31] W·m -2 across exercise bouts (acclimation effect: P < 0.001; interaction: P = 0.598). This was paralleled by reductions in core temperature and heart rate of 0.3 [0.2, 0.4] °C and 11 [8, 14] beats·min -1 (both, acclimation effect: P < 0.001; interaction: P = 0.288), respectively. CONCLUSIONS: Seven consecutive days of warm water immersion improved whole-body heat loss and reduced core temperature and cardiovascular strain across light-to-vigorous intensity exercise in habitually active older men. Passive heat acclimation may be an efficacious alternative to exercise heat acclimation to improve heat loss capacity. Studies are warranted to assess effectiveness in more heat-vulnerable populations.
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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".