Hypothalamic-pituitary-adrenal Axis And The Sympathetic-adrenomedullary System Responses During Heat Acclimation In Sedentary Males
Bibliographic record
Abstract
Previous research suggests that the release of HPA and SAS stress hormones are functionally linked to the increase in core temperature during exercise and heat stress exposure. Yet, heat acclimation is known to increase tolerance time and the core temperature tolerated during uncompensable heat stress (UHS), and reduce physiological strain. It would be of interest, therefore, to know whether the HPA and SAS hormone response following heat acclimation is reduced at any given level of thermal strain. PURPOSE: To examine the HPA and SAS stress hormone responses in sedentary males during 9 days of exposure to UHS. METHODS: Nine sedentary males (Mean±SE: VO2peak= 51.7±1.9 mL·kgLBM-1·min-1, 17±2% fat) walked to exhaustion (EXH) on 9 days (over 2 consecutive weeks) on a treadmill (4.5 km·h-1, 2% incline) in 40°C and 30% R.H., wearing combat clothing and a protective hooded overgarment. At rest (PRE; prior to heat) and at a Tre of 38, 38.5, 39°C, and EXH venous blood samples were obtained. COR, GH, and ACTH were determined by chemiluminescence and NE and E by gas chromatography/mass spectrometry. RESULTS: Although Tre EXH was not different from Day 1 (38.8±0.1°C) to 9 (39.1±0.1°C), time to EXH increased from 95±8 to 145±13 min. Significant increases were observed from PRE to EXH for COR (357.0±8.5 to 491.3±18.8 nmol·L-1), ACTH (4.7±0.2 to 21.7±1.9 pmol·L-1), NE (1.9±0.0 to 4.7±0.0 nmol·L-1), and E (208.4±3.5 to 547.5±18.9 pmol·L-1) that were unaffected by heat acclimation. No differences also were observed between Day 1 and 9 from Pre to 39°C for COR, ACTH, NE, and E (p≤0.1). However, GH EXH on Day 1 (9.9±1.7 mIU·mL-1) was significantly greater than Days 5, 6, and 9 (6.5±0.9, 6.4±0.9, and 7.7±0.2 mIU·mL-1, respectively). CONCLUSION: Nine days of exertional heat acclimation improved the GH stress response, yet COR, ACTH, NE, and E remained temperature driven. Funded by a DRDC Technology Investment Fund.
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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".