Prolactin, Tryptophan, and Branch Chain Amino Acids, and Relationships with Psychomotor Performance during Heat Stress
Bibliographic record
Abstract
Changes in Prolactin (PRL) and the ratio of Tryptophan (TRYP) to Branch Chain Amino Acids (BCAA) during stress have been identified as indicators of central fatigue. Research suggests that an increase in rectal temperature (Tre) impairs psychomotor function, due to increased perceived discomfort and fatigue; however the relationship to the changes in purported neuroendocrine markers of central fatigue is unclear, particularly during uncompensable heat stress. PURPOSE: The purpose was to examine the relationship between psychomotor performance and neuroendocrine markers of central fatigue during acute uncompensable heat stress to exhaustion. METHODS: Twelve trained and eleven untrained males (Mean±SE: VO2peak=70±2 and 50±1 mL·kgLBM−1·min−1, 11±1 and 16±1% fat, respectively) walked to exhaustion (Tre= 39.7 and 39.0°C, respectively) on a treadmill (4.5 km·h−1, 2% grade) in 40°C and 30% R.H., wearing combat clothing and a protective hooded overgarment. At a Tre of 38.0, 38.5, 39.0°C, and exhaustion (EXH) venous blood samples were obtained and subjects performed a Psychomotor Vigilance Task (PVT) for reaction time (RT), false starts, and lapses (RT>0.5s). Serum was analyzed for PRL using a chemiluminescent immunoassay, and plasma analyzed for BCAA and TRYP using gas chromatography/mass spectrometry. Perceptual Strain Index (PeSI) was calculated based on thermal comfort and perceived exertion ratings. RESULTS: PRL, TRYP, and PeSI increased with Tre from 38°C to EXH (p<0.05) but were not related to changes in reaction time, lapses, or false starts for either group. BCAA decreased (38°C to EXH: 374 ± 23 to 348 ± 21 nmol/mL) with increasing Tre and was related to the increase of reaction time for UT (r=−0.62, p<0.05). There was a trend toward slower reaction times in TR and UT from 38°C (257 ± 9 and 277 ± 21 msec, respectively) to EXH (270 ± 9 and 314 ± 29 msec, respectively) (p<0.06). No relationship was observed between the change in TRYP/BCAA and measures of psychomotor performance for either group. CONCLUSIONS: Changes in PRL or TRYP/BCAA, as indicators of central fatigue, were not related to measures of psychomotor performance in TR or UT, however changes in BCAA alone were related to changes in psychomotor performance for UT. Funded by a Defence R&D Canada 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 | 0.001 |
| 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".