Impact of preinduced quadriceps fatigue on exercise response in chronic obstructive pulmonary disease and healthy subjects
Bibliographic record
Abstract
Exercise intolerance in chronic obstructive pulmonary disease (COPD) results from a complex interaction between central (ventilatory) and peripheral (limb muscles) components of exercise limitation. The purpose of this study was to evaluate the influence of quadriceps muscle fatigue on exercise tolerance and ventilatory response during constant-workrate cycling exercise testing (CWT) in patients with COPD and healthy subjects. Fifteen patients with COPD and nine age-matched healthy subjects performed, 7 days apart, two CWTs up to exhaustion at 80% of their predetermined maximal work capacity. In a randomized order, one test was performed with preinduced quadriceps fatigue and the other in a fresh state. Quadriceps fatigue was produced by electrostimulation-induced contractions and quantified by maximal voluntary contraction and potentiated twitch force (TwQ(pot)). Endurance time and ventilatory response during CWT were compared between fatigued and fresh state. Endurance time significantly decreased in the fatigued state compared with the fresh condition in COPD (356 +/- 69 s vs. 294 +/- 45 s, P < 0.05) and controls (450 +/- 74 s vs. 340 +/- 45 s, P < 0.05). Controls showed significantly higher ventilation and end-exercise dyspnea scores in the fatigued condition, whereas, in COPD, fatigue did not influence ventilation or dyspnea during exercise. The degree of ventilatory limitation, as expressed by the Ve/maximum voluntary ventilation ratio, was similar in both conditions in patients with COPD. We conclude that it is possible to induce quadriceps fatigue by local electrostimulation-induced contractions. Our findings demonstrate that peripheral muscle fatigue is an additional important factor, besides intense dyspnea, that limits exercise tolerance in 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".