Force depression following muscle shortening of voluntarily activated and electrically stimulated human adductor pollicis
Notice bibliographique
Résumé
The purpose of this study was to investigate steady-state force depression following active muscle shortening in human adductor pollicis during voluntary and electrically induced contractions. Subjects (n = 12; age 28 +/- 5 years; 7 males and 5 females) performed isometric reference contractions and isometric-shortening-isometric contractions, using maximal voluntary effort and near-maximal electrical stimulation. Force depression was assessed by comparing the steady-state isometric forces produced following active muscle shortening with the purely isometric reference forces obtained at the corresponding muscle length. In order to test for effects of the shortening conditions on the steady-state force depression, the amplitude and speed of shortening were changed systematically in a random order but balanced design. Thumb adduction force and carpometacarpal joint angle were continuously measured using a custom-designed dynamometer. During voluntary contractions, muscle activation was recorded using electromyography and the superimposed twitch technique. During electrically induced contractions, muscle stiffness was assessed using a quick-stretch method. Force depression during voluntary contractions, with a constant level of muscle activation, was similar to that obtained during electrically induced contractions. Force depression increased with increasing amplitudes of shortening (9.9 +/- 1.6%, 15.6 +/- 2.4% and 22.4 +/- 2.4% for 10, 20 and 30 deg of shortening, respectively) and decreased with increasing speeds of shortening (27.1 +/- 2.5%, 19.3 +/- 1.6% and 15.6 +/- 1.8% for 20, 60 and 300 deg s(-1) of shortening, respectively), regardless of the activation method. Muscle stiffness was significantly lower in the force-depressed state (5.9 +/- 0.2 N deg(-1)) compared with that of the isometric reference contractions (7.2 +/- 0.3 N deg(-1)), and decreased with increasing force depression (6.6 +/- 0.5, 6.0 +/- 0.5 and 5.3 +/- 0.4 N deg(-1) for the 10, 20 and 30 deg of shortening test contractions, respectively). Force depression appeared to be fully established at the end of the shortening phase. The results of this study suggest that steady-state force depression for voluntary movements is similar to that observed using electrical stimulation. Furthermore, it appears that force depression is established at the end of the shortening phase and is associated with a reduction in muscle stiffness and thus, presumably, a decrease in the proportion of attached cross-bridges.
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Comment cette classification a été obtenuedéplier
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 | 0,000 | 0,000 |
| 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) | 0,000 | 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 ».