Trinchi Michele, Bizet Baptiste, Zamparo Paola, Monte Andrea
Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy.
Scand J Med Sci Sports. 2025 Jul;35(7):e70103. doi: 10.1111/sms.70103.
Skeletal muscle is heterogeneous in its architecture, with regional differences in fiber length and pennation angle that make up anatomically distinct regions. This study aimed to understand how these regional differences influence vastus lateralis (VL) behavior during isokinetic contractions in vivo. Knee extensor torque was measured in twelve healthy young adults using an isokinetic dynamometer during maximal contractions at different angular velocities (30° s, 75° s, 150° s, 210° s, 270° s). The fascicle length of VL was recorded by two ultrasound devices in its distal and middle regions, and muscle-belly length was calculated as the longitudinal length change in the muscle belly. Fascicle (Vf) and muscle-belly (Vm) velocities were calculated as the first derivative of the length-time curve in the phase at constant angular velocity. Muscle-belly gearing (Gb) was calculated as Vm/Vf. At rest, greater thickness and pennation angles and lower fascicle lengths were observed in the middle vs. distal regions. During contraction, Vf and Vm increased as a function of angular velocity in both the investigated regions. The distal regions showed higher Vf and Vm values at all the investigated angular velocities. Significant differences in Gb were observed between regions but not as a function of knee angular velocity. Our data indicate that the architectural differences within a muscle affect the behavior of the active components during contraction. These results could help develop new musculoskeletal models to predict the muscle's mechanical output better.
骨骼肌在结构上具有异质性，其纤维长度和羽状角存在区域差异，从而构成了解剖学上不同的区域。本研究旨在了解这些区域差异如何影响活体等速收缩过程中股外侧肌（VL）的行为。在十二名健康年轻成年人中，使用等速测力计在不同角速度（30°/秒、75°/秒、150°/秒、210°/秒、270°/秒）下进行最大收缩时测量膝关节伸肌扭矩。通过两个超声设备记录VL远端和中部区域的肌束长度，并将肌腹长度计算为肌腹的纵向长度变化。肌束（Vf）和肌腹（Vm）速度计算为等角速度阶段长度-时间曲线的一阶导数。肌腹传动比（Gb）计算为Vm/Vf。在静息状态下，中部区域与远端区域相比，观察到更厚的厚度、更大的羽状角和更低的肌束长度。在收缩过程中，两个研究区域的Vf和Vm均随角速度增加。在所有研究的角速度下，远端区域的Vf和Vm值均较高。区域之间观察到Gb存在显著差异，但与膝关节角速度无关。我们的数据表明，肌肉内的结构差异会影响收缩过程中活性成分的行为。这些结果有助于开发新的肌肉骨骼模型，以更好地预测肌肉的机械输出。
