Cardiovascular and Thermal Responses to Repeated Head-Up Tilts Following Exercise-Induced Heat Stress
Bibliographic record
Abstract
BACKGROUND: We evaluated the acute cardiovascular and thermoregulatory responses to repeated 70 degrees head-up tilts (HUT) performed following exercise-induced hyperthermia. METHODS: Eight male subjects underwent intermittent episodes of 70 degrees HUT in either a non-exercise/ non-heat stress state (NH) or an exercise-induced hyperthermic state (EIH). Subjects remained supine for 30 min in a thermoneutral environment (22 degrees C) and were subsequently exposed to three successive 6-min 70 degrees head-up tilts (HUT1, HUT2, HUT3), each separated by 10 min of supine resting. During EIH, subjects were rendered hyperthermic by exercise in the heat (core temperature of approximately 40.0 degrees C) and were then transferred to an ambient temperature of 22 degrees C. We evaluated the relative change in hemodynamic and thermal responses from the last minute in the supine position preceding the HUT to the final minute in HUT. RESULTS: While we measured a difference in the relative change in heart rate between conditions for all HUTs, no differences were observed in mean arterial pressure (MAP), total peripheral resistance, or cardiac output. A reduced change in baroreceptor sensitivity was measured in EIH for HUT1 only (-2 +/- 1 ms x mmHg(-1) following EIH compared to -13 +/- 3 ms x mmHg(-1) during NH). A significant transient reduction in cutaneous vascular conductance (CVC) occurred during HUT1 and HUT2 following EIH (-20 +/- 5% CVCmax and -9 +/- 3 %CVCmax, respectively), despite significant elevations in core temperature above resting levels (i.e., 1.4 degrees C and 0.9 degrees C for HUT1 and HUT2). CONCLUSION: We conclude that the maintenance of MAP following exercise in the heat is mitigated by reductions in skin perfusion despite significant elevations in core temperature.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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) | 0.000 | 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 teacher head, 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".