Institute of Movement Sciences, Aix-Marseille University, CNRS, ISM, Marseille, FRANCE.
Department of Movement, Sciences, Decathlon Sports Lab, Villeneuve d'Ascq, FRANCE.
Med Sci Sports Exerc. 2018 Nov;50(11):2311-2321. doi: 10.1249/MSS.0000000000001690.
Because the hand joints possess a broad range of motion, the muscle length can vary importantly which might result in significant variations of the muscle force-generating capacities. However, facing the complexity of this musculoskeletal system, no study has examined the effect of hand muscle length change on muscle force. This study aimed to characterize the force-length relationship of muscles involved in wrist and metacarpophalangeal flexion.
Eleven participants performed two sessions: (i) one for the wrist flexor muscles and (ii) one for the finger flexor muscles. For each session, the participants performed two maximal voluntary contractions and then two progressive isometric ramps from 0% to 100% of their maximal force capacity at five different wrist/metacarpophalangeal angles. Torque, kinematic, and electromyographic data were recorded. An ultrasound scanner was used to measure the myotendinous junction displacement of flexor carpi radialis (FCR) and flexor digitorum superficialis (FDS) during isometric contractions. A three-dimensional relationship between muscle length, force, and activation level was modeled using optimization procedure.
Globally, the FCR was stronger and shorter compared with FDS. The results showed that the three-dimensional relationships fitted well the experimental data (mean R = 0.92 ± 0.07 and 0.87 ± 0.11 for FCR and FDS, respectively). Using joint angle and EMG data, this approach allows to estimate the muscle force with low estimation errors (<9% of Fmax).
This study proposes a new method to investigate the force-length relationship by combining ultrasound measurement, musculoskeletal modeling and optimization procedures. The data and relationships provide a new insight into hand biomechanics and muscle function that could be useful for designing hand tools or surgical operations.
由于手部关节具有广泛的运动范围，肌肉长度可能会发生重要变化，这可能导致肌肉产生力量的能力发生显著变化。然而，面对这个复杂的肌肉骨骼系统，还没有研究检查手部肌肉长度变化对肌肉力量的影响。本研究旨在描述腕关节和掌指关节屈曲的肌肉的力-长度关系。
11 名参与者完成了两个阶段的实验：（i）腕屈肌阶段，（ii）指屈肌阶段。对于每个阶段，参与者进行了两次最大自主收缩，然后在五个不同的腕关节/掌指关节角度下，以 0%到 100%的最大力量能力进行两次递增的等长斜坡。记录扭矩、运动学和肌电图数据。使用超声扫描仪在等长收缩过程中测量桡侧腕屈肌（FCR）和指浅屈肌（FDS）的肌肌腱结合部位移。使用优化程序对肌肉长度、力量和激活水平的三维关系进行建模。
总体而言，FCR 比 FDS 更强壮且更短。结果表明，三维关系很好地拟合了实验数据（FCR 和 FDS 的平均 R 值分别为 0.92 ± 0.07 和 0.87 ± 0.11）。使用关节角度和肌电图数据，这种方法可以以较低的估计误差（<9%的 Fmax）估计肌肉力量。
本研究提出了一种新的方法，通过结合超声测量、肌肉骨骼建模和优化程序来研究力-长度关系。这些数据和关系为手部生物力学和肌肉功能提供了新的见解，这对于设计手部工具或手术操作可能是有用的。
