DISTAL AND PROXIMAL FASCICLE LENGTH CHANGES IN ACTIVE AND PASSIVE HUMAN GASTROCNEMIUS MUSCLE
Notice bibliographique
Résumé
INTRODUCTION Skeletal muscle is composed of structural units of decreasing size, with muscle fascicles as the largest unit and sarcomeres as the smallest unit [1]. Fascicles define the overall muscle architecture. Because architecture is specific to individual muscles, knowing fascicle length is essential for understanding contraction and force production. Ultrasound imaging allows for in vivo studies of fascicle lengths. Muscle architecture has been studied extensively in the human gastrocnemius at the mid-belly region [2]. However, the mid-belly might not reflect muscle architecture accurately across the entire muscle. Therefore, the objective of this study was to measure human gastrocnemius fascicle lengths at a distal and a proximal location. METHODS Fifteen healthy male subjects were tested (age: 25±5yrs; height: 177±8cm; weight: 69±8kg). Each subject was positioned in an isokinetic dynamometer with the right knee joint at full extension. The ankle joint was fixed at -10o dorsiflexion and 0, 10o, 20o, 30o, and 40o plantar flexion. Ankle torque and fascicle length were measured at rest (passive) and for maximum voluntary isometric plantar flexion (active) contractions, with an ultrasound probe close to the myotendinous junction of the gastrocnemius (distal). All testing was then repeated with the probe positioned close to the knee joint (proximal). A three way ANOVA was used to assess fascicle length with the main factors: torque (passive and active), location (distal and proximal), and ankle joint angle (-10o, 0, 10o, 20°, 30o, 40o) at a level of significance of α=0.05. Bonferroni post-hoc testing was performed when indicated. RESULTS Passive fascicle length was greater in more dorsiflexed positions than plantarflexed positions at distal and proximal locations (P<0.001). There was significant fascicle shortening from passive to active states (P<0.001). Passive fascicle lengths were greater at 0o, 10o, and 20o plantar flexion at the distal compared to the proximal location (P<0.05; Fig. 1). Distal and proximal active fascicle lengths were the same at all ankle angles. (Fig 1).DISCUSSION AND CONCLUSIONS Active fascicle lengths were the same at distal and proximal locations across all ankle angles. Passive fascicle lengths were longer distally compared to proximally, suggesting that the relative fascicle shortening from passive to active states depends on location along the muscle. Therefore, absolute sarcomere lengths must differ between distal and proximal fascicles, at least for some conditions. This result brings into question the long-held belief that sarcomere lengths in a given muscle are the same at all locations and independent of the instantaneous contractile conditions. Careful analysis of this result is required for generalization of the current results across other muscles.
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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 | 0,001 | 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 | 0,001 |
| 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.
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