Acute Effect of Heat Exposure on Brachial Artery FMD: Impact of Modality and Measurement Timeline
Bibliographic record
Abstract
Introduction Heat exposure is receiving a lot of attention for its potential to improve endothelial function, as measured by brachial artery flow‐mediated dilation (FMD). Although most intervention studies have observed an improvement in brachial artery FMD, the acute effect of heat exposure has been inconsistent. This observation likely stems from the various modalities employed (local limb heating to whole‐body heating) and the timing of FMD measurement following the heating intervention (immediately after up to 60 min post‐heating). Identifying a heating modality that consistently improves brachial artery FMD and establishing the timeline of the response would facilitate investigations into potential mechanisms mediating heat‐induced improvements in brachial artery FMD without the need of more challenging intervention studies. The aims of this study are to 1) determine the acute effect of four heating interventions on brachial artery FMD, and 2) characterize the time‐dependent changes in brachial artery FMD following each intervention. Methods On separate days, 11 young and healthy adults (3F/8M; 29±6 y; 66.5±9.4 kg; 1.7±0.1 m) were exposed to: i) 10 minutes of forearm heating using an electric blanket (EB); ii) 30 minutes of forearm heating in 40˚C water (WI); iii) 60 minutes of whole‐body heating where the arm used to assess brachial artery FMD was not covered by the water perfused suit (WHB‐U), or; iv) was covered for the entire 60 minutes of whole‐body heating with the suit (WBH‐C). During each trial, brachial artery FMD was measured prior to the heating intervention (baseline), within 5 minutes following the end of the intervention, and every 30 minutes for two hours following the intervention. Results Mean shear rate increased from baseline during the WI (+78±43 s ‐1 , P=0.02), WBH‐U (+177±99 s ‐1 , P<0.01) and WBH‐C (+140±43 s ‐1 , P<0.01) interventions, but not during EB (+18±35 s ‐1 , P=0.37). Brachial artery FMD was unaffected by the EB intervention (P=0.39). Conversely, there was a main effect of time for FMD during the WI (P=0.03), WBH‐U (P<0.01), and WBH‐C (P<0.01) interventions. Specifically, FMD was greater relative to baseline, 90 minutes following the WI intervention (+3.7±3.3%, P=0.03, increase in 8/11 participants). A lower FMD relative to baseline was observed within 5 minutes of the end of the WBH‐U (‐4.5±3.7%, P<0.01, decrease in 9/11 participants) and WBH‐C (WBH‐C: ‐6.1±3.5%, P<0.01, decrease in 10/11 participants) interventions. Conclusion These results suggest that 10 minutes of local heating with an electric blanket may not modulate brachial FMD, whereas whole‐body heating with or without local heating of the arm causes a temporary reduction in FMD. Forearm immersion in 40°C water for 30 minutes was the only intervention that consistently improved brachial artery FMD, but only when measured 90 minutes following the intervention.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 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 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 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".