Exercise Endurance is Increased by Slowed Peripheral Fatigue in Older Subjects Breathing Heliox
Bibliographic record
Abstract
Despite a number of studies on healthy humans investigating the role of unloading the respiratory muscles with heliox (He-O2), there is no agreement as to what extent exercise endurance is affected. Furthermore, the role of He-O2 on the components of fatigue (central vs peripheral) has not been investigated. PURPOSE: This study was aimed at investigating the role of He-O2 on exercise endurance and neuromuscular function following exercise in healthy humans. METHODS: Nine younger males (30-40 years old) and ten older males (55-70 years old) participated in the study. After screening tests (pulmonary function test and incremental exercise test), each subject performed two constant power output (75% of peak power output) cycling tasks to exhaustion in random order, breathing either medical air (Air) or He-O2 and, finally, the same test while breathing He-O2 for the same duration as the exercise with Air breathing (ISO). RESULTS: In younger subjects, exercise duration was not different (P>0.71) with He-O2 599±55 s relative to Air 617±55 s and the amount of peripheral quadriceps fatigue, indicated by reduced twitch amplitude, was similar for all conditions. In older subjects, in contrast, exercise duration was significantly increased (P<0.05) during He-O2 (960±175 s) relative to Air (837±168 s) and peripheral quadriceps fatigue was similar for He-O2 and Air in spite of different exercise durations. However, the amount of peripheral fatigue was less for ISO (P<0.05), indicating a slower rate of decline when these subjects breathed He-O2. CONCLUSIONS: These findings suggest that in older subjects, He-O2 probably unloaded the respiratory muscles (reduced work of breathing) so they were able to exercise longer at the required intensity. The slower rate of fatigue with He-O2 indicates that subjects were better able to perfuse their exercising muscles when breathing He-O2. In contrast, we think that the effect of heliox was absent at the 75% of peak power output in younger subjects because it either did not unload the respiratory muscles, or the cardiac output capability was not taxed to the same extent as the older subjects. In both groups, EMG activity did not reveal impairment of muscle activation showing that the central nervous system was still capable of activating the muscles. However, the muscle response to this activation was less than it had been prior to the exercise, confirming the presence of peripheral fatigue. We interpreted these findings to mean that peripheral muscle fatigue plays an important role in regulating exercise endurance in these individuals performing cycling exercise at 75% of maximal power output. Research supported by NSERC, Canada
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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 | 0.002 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.003 |
| Science and technology studies | 0.000 | 0.002 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".