Cerebral Water and Ion Balance Remains Stable when Humans Are Exposed to Acute Hypoxic Exercise
Bibliographic record
Abstract
BACKGROUND: Intense physical activity increases the prevalence of acute mountain sickness (AMS) that can occur within 10 h after ascent to altitudes above 1500 m and is likely related to development of cerebral edema. This study evaluated whether disturbed cerebral water and ion homeostasis can be detected when intense exercise is carried out in hypoxia and monitored the influence of muscle metabolism for changes in arterial variables. METHODS: On two separate days, in random order, 30 min cycling exercise was performed in either hypoxia (10% O2) or normoxia at an intensity that was exhaustive in the hypoxic trial (∼120 W; n=9). RESULTS: Exercise in hypoxia affected muscle metabolism, as evidenced by higher (p<0.05) leg lactate release at 7.5 min and a continuous decline in arterial pH (p<0.001) that was not observed in normoxia. Middle cerebral artery flow velocity increased (p<0.01) with exercise under both circumstances. No cerebral net exchange of Na(+) or K(+) was evident. Likewise, no significant net-exchange of water over the brain was demonstrated and the arterial and jugular venous hemoglobin concentrations were similar. CONCLUSION: Challenging exercise in hypoxia for 30 min affected muscle metabolism and increased an index of cerebral blood flow, but cerebral net water and ion homeostasis remained stable. Thus, although AMS develops within hours and may be related to exercise-induced disturbance of cerebral ion and water balance, such changes are not detectable when subjects are exposed to acute 30 min maximal exercise in hypoxia.
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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".