Effects Of Exercise-induced Respiratory Muscle Work And Hypoxemia On Quadriceps Fatigue In Men Versus Women
Bibliographic record
Abstract
Reducing work of breathing (WOB) or eliminating exercise-induced arterial hypoxemia (EIAH) during intense exercise decreases the severity of quadriceps fatigue in men. Women have a greater WOB at any given ventilation during exercise relative to men, dedicate a greater fraction of whole body V[Combining Dot Above]O2 towards their respiratory muscles, and demonstrate EIAH, suggesting women may be more susceptible to quadriceps muscle fatigue. PURPOSE:To determine the extent to which quadriceps fatigue is attenuated when WOB is reduced or EIAH is prevented during exercise in both sexes. METHODS:Six healthy subjects (V[Combining Dot Above]O2max57±2 ml/kg/min; 3 female) completed maximal incremental cycle exercise and 3 time-to-exhaustion (TTE) tests over 4 days. During the first (control) TTE test, subjects exercised at constant work rate (>85% of max work) while temperature-corrected arterial blood gases, cardiorespiratory variables and WOB were assessed. Subsequent TTE tests were iso-time and iso-work rate, but with EIAH prevented by inspiring hyperoxic gas (24-27% O2) or WOB reduced via a proportional assist ventilator (PAV). Locomotor muscle fatigue was assessed by measuring potentiated quadriceps twitch force in response to supramaximal magnetic stimulation of the femoral nerve before and 3 min after exercise. RESULTS:Men exercised at a higher absolute work rate (273±9 vs. 203±12 W,p>.05) as women. During the control TTE (data pooled), nadir arterial oxyhemoglobin saturation (SaO2) was 95±0.4% and pHa was 7.18±0.03. Hyperoxia prevented EIAH in all subjects (SaO2>98%). PAV reduced WOB to 58±6% of control (range 35-75%). Quadriceps twitch force was reduced after the control exercise trial by 26±3% and was significantly attenuated after exercise on the hyperoxia and PAV trials (19±3 and 19±3%, p>.01, respectively). The subject with the largest increase in SaO2 (+9%) with hyperoxia and the greatest reduction in WOB (35% of control) with PAV had the greatest attenuation of locomotor fatigue. CONCLUSIONS:Preventing EIAH and reducing WOB attenuate post-exercise quadriceps fatigue to a similar extent in both sexes. Subjects with the highest WOB or lowest SaO2 during the control trial demonstrated the greatest attenuation of quadriceps fatigue during the PAV and hyperoxic trials. Funding: NSERC
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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) | 0.003 | 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".