Effects of a low-intensity single-leg exercise on fatigue and muscle oxygenation in patients with chronic obstructive pulmonary disease (COPD)
Bibliographic record
Abstract
In COPD, single-leg exercises allow to study muscle dysfunction mechanisms in isolation from exagerated ventilatory demand and dyspnea. Therefore, we studied the effect of a knee-extension exercise on quadriceps fatigue and its possible association with cardiorespiratory demand and oxygen extraction at the muscle level. Methods: Eight patients with moderate-to-severe COPD (FEV 1 = 45 ± 13% of predicted) performed an isokinetic knee-extension exercise at 40% of their maximal peak torque. Quadriceps isometric maximal voluntary contraction (MVC) and magnetic-stimulated twitch (Tw pot ) were measured before and after exercise to characterize muscle fatigue. Cardiorespiratory demand and muscle oxygenation (deoxyhemoglobin/myoglobin concentration, [HHb], by near-infrared spectroscopy) were assessed during exercise. Results: Patients performed a total of 7.4 ± 1.0 kJ of muscle work, which resulted in a reduction of both MVC and Tw pot of -11 ± 8 % and -22 ± 25 %, respectively. Five patients presented muscle fatigue (> 15 % reduction in Tw pot ). At the end of exercise, dyspnea and leg-fatigue Borg scores were 2.0 ± 1.0 and 0.7 ± 0.8, respectively. No significant changes in muscle oxygenation (Δ[HHb] = 13 ± 12%, p = 0.08) were seen. Changes in muscle oxygenation were not associated with muscle strength loss. Peak minute ventilation and oxygen uptake represented, on average, 50% and 41% of peak value achieved during a symptom-limited maximal exercise test. Conclusion: Despite low cardiorespiratory demand and exercise load, a single-leg exercise induced muscle fatigue in the absence of muscle deoxygenation in some patients with moderate-to-severe COPD.
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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".