Feet-heating and calf-heating have opposing effects on glucose tolerance and heart rate variability: a randomized, controlled, crossover trial
Bibliographic record
Abstract
Heat exposure’s effect on glucose tolerance depends on the amount of body exposed, likely relating to autonomic nervous system balance. We assessed how partial-body heat exposure at two different levels of the lower extremities affects glucose tolerance and autonomic nervous system balance, measured via heart rate variability. We hypothesized feet-heating would improve glucose tolerance without affecting heart rate variability, while calf-heating would worsen glucose tolerance and decrease heart rate variability compared to a thermoneutral control condition. In a randomized, controlled, crossover trial, healthy participants’ ( N = 31, 23(3) years, 45% male) glucose tolerance was measured in (A) thermoneutral; (B) feet-heating; and (C) calf-heating conditions. Every 30 min for 2 h, blood glucose, heart rate, heart rate variability, tympanic temperature, thermal comfort scores, and blood pressure were measured. There were significant interactions between condition and time for blood glucose ( F (4.6,72.6) = 2.6, p = 0.036), heart rate ( F (3.4, 54.5) = 3.5, p = 0.017), heart rate variability ( F (4.3,63.2) = 7.5, p < .0001), tympanic temperature ( F (8, 268) = 2.4, p = 0.014), and thermal comfort scores ( F (8, 248) = 22.1, p < 0.0001). Calf-heating increased 90 min glucose (+12 (95% confidence interval, CI: 3–21) mg/dL, p = 0.013) and decreased heart rate variability throughout (mean decrease: 13%–22%, p < 0.007), while feet-heating lowered 90 min glucose (−7 (95% CI: −16 to +1) mg/dL, p = 0.090) without affecting heart rate variability ( p = 0.14–0.99). Blood pressure and body temperature were similar between conditions, but heart rate and thermal comfort scores increased with heating. Calf-heating worsens, while feet-heating may improve, glucose tolerance. Changes in heart rate variability coincided with changes in glucose tolerance despite unchanged body temperature. Whether heart rate variability can be used to monitor autonomic nervous system balance during heating to optimize its acute effect on glycemic indices should be further explored.
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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 | 0.003 | 0.003 |
| Meta-epidemiology (narrow) | 0.002 | 0.001 |
| Meta-epidemiology (broad) | 0.004 | 0.001 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.001 | 0.002 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.002 | 0.003 |
| Insufficient payload (model declined to judge) | 0.006 | 0.001 |
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".