Neuroendocrine Response In Trained Versus Untrained Individuals During Exertional Heat Stress
Bibliographic record
Abstract
Understanding the neuroendocrine changes that occur during heat stress in trained (TR) versus untrained (UT) individuals may assist in identifying the mechanisms behind improved thermotolerance in trained individuals. Present knowledge suggests that an increase in core temperature is necessary for certain hormonal changes to be evident during acute exercise. However, the impact of core temperature on the neuroendocrine response in TR and UT individuals is unclear. PURPOSE: The purpose of this study was to examine how the neuroendocrine response to acute heat stress in UT individuals compared to TR individuals at the same core temperature levels. METHODS: Five UT males (Mean±SE: VO2peak= 48 ± 2 mL·kgLBM·mm−1, 14 ± 3% fat, 20.8 ± 5.8y) and ten TR males (VO2peak= 68 ± 4 mL-kgLBM−1min−1, 10 ± 4 % fat, 24.2 ± 4.3y) walked to exhaustion on a treadmill (4.5 km·h−1, 2% grade) in 40°C and 30% RH while wearing combat clothing and a protective overgarment with hood. Rectal temperature (Tre) reached 39.1 ± 0.1°C (UT) and 39.7 ± 0.1°C (TR). Venous blood samples were obtained at baseline (prior to the heat stress trial), and at T of 38.0, 38.5, 39.0°C, and exhaustion. Blood was centrifuged, separated, and serum stored frozen until analyzed for prolactin (PRL), growth hormone (GH), dehydroepiandrosterone (DHEA), cortisol (COR), and adrenocorticotrophic hormone (ACTH) using a chemiluminescent immunoassay (Immulite®). RESULTS: Despite different relative intensities of exercise during the acute heat stress (TR = 27 ± 1, UT = 37 ± 2% of VO2peak), there were no differences between TR and UT for PRL, DHEA, COR, and ACTH at the same T and at exhaustion. In contrast, GH was elevated at 38.0, 38.5, and 39.0°C in TR (15.9 ± 2.9, 17.3 ±2.2, and 15.7 ±2.6 μg·mL−1, respectively) versus UT (8.4 ± 1.9, 6.4 ± 1.3, and 5.5 ± 1.1 μg·mL−1, respectively) but there was no difference at exhaustion (12.0 ±3.4 and 7.6 ± 2.5 μg·mL1, respectively). PRL, DHEA, COR, and ACTH increased significantly across exercise duration, where GH peaked at a Tre of 38.0°C. CONCLUSION: In summary, PRL, DHEA, COR, and ACTH responses during acute heat stress were related to the level of Tre and independent of fitness level, whereas growth hormone response was influenced by both Tre and fitness level. Research was funded by a DRDC technology Investment Fund.
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 | 0.000 | 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".