Metabolite Accumulation And Power Output During And After Fatiguing Exercise In Young And Older Adults
Notice bibliographique
Résumé
Fatigability of limb muscles during high-intensity dynamic exercise is postulated to be determined by the accumulation of metabolites, namely hydrogen ions (H+) and inorganic phosphate (Pi). We previously showed that the increased fatigability of older adults during dynamic exercise was accompanied by a greater accumulation of metabolites compared with young adults. However, the time course of metabolite accumulation in relation to power output during and after dynamic fatiguing exercise is unknown. PURPOSE: Determine the time course of metabolite accumulation and changes in power during lower limb fatiguing exercise and recovery in young and older adults. METHODS: 9 young (20-36 yrs; 5 women) and 8 older adults (69-77 yrs; 4 women) performed a 4-min fatiguing knee extension exercise (1 maximal velocity contraction every 2 s) lifting a load equivalent to 20% of their maximal voluntary isometric contraction while prone in the bore of an MRI scanner. Recovery was measured with sets of 5 maximal dynamic contractions (1 every 2 s) at 30, 60, 150, 300, and 600 s after exercise. Intramuscular [Pi] and [H+] were measured with 31P-MRS, and statistical parametric mapping was used to evaluate the time course differences between the metabolite accumulation and power during exercise and recovery. RESULTS: Fatigability was ~1.6-fold greater in older than young adults (P < 0.001), which was accompanied by a greater decrease in pH (6.71 ± 0.07 vs. 6.62 ± 0.10, P = 0.043) and increase in Pi (24.7 ± 2.4 mM vs. 32.2 ± 5.6 mM, P = 0.002) by the end of exercise. Except for the first 32 s of exercise where pH increased while power decreased, the time course of H+ accumulation and power loss was similar. However, after exercise H+ continued to increase for 60s as power was recovering. In contrast, Pi accumulated more rapidly than the loss in power for the first 152 s of exercise, after which Pi no longer accumulated but power continued to decrease. After exercise, the recovery of power and Pi followed a similar time course. There were no age effects on the relationship between power output and metabolites at any time point during or after exercise. CONCLUSIONS: These data suggest that both H+ and Pi are essential metabolites disrupting power during and in recovery from fatiguing exercise and that the effects of these metabolites are similar in young and older adults. Supported by NIA R01 grant (AG048262) to Christopher Sundberg, Robert Fitts and Sandra Hunter.
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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,001 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 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 source (Gemma direct ou Codex distillé), 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 ».