Exercise Endurance is Increased by Slowed Peripheral Fatigue in Older Subjects Breathing Heliox
Notice bibliographique
Résumé
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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Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,002 | 0,001 |
| Méta-épidémiologie (sens strict) | 0,001 | 0,000 |
| Méta-épidémiologie (sens large) | 0,001 | 0,000 |
| Bibliométrie | 0,001 | 0,003 |
| Études des sciences et des technologies | 0,000 | 0,002 |
| Communication savante | 0,000 | 0,001 |
| Science ouverte | 0,001 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,001 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,002 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».