Stäudle Benjamin, Seynnes Olivier, Laps Guido, Brüggemann Gert-Peter, Albracht Kirsten
Faculty of Medical Engineering and Technomathematics, Aachen University of Applied Sciences, Aachen, Germany.
Institute of Movement and Neurosciences, German Sport University Cologne, Cologne, Germany.
Front Physiol. 2022 Mar 1;13:792576. doi: 10.3389/fphys.2022.792576. eCollection 2022.
Achilles tendon rupture (ATR) remains associated with functional limitations years after injury. Architectural remodeling of the gastrocnemius medialis (GM) muscle is typically observed in the affected leg and may compensate force deficits caused by a longer tendon. Yet patients seem to retain functional limitations during-low-force-walking gait. To explore the potential limits imposed by the remodeled GM muscle-tendon unit (MTU) on walking gait, we examined the contractile behavior of muscle fascicles during the stance phase. In a cross-sectional design, we studied nine former patients (males; age: 45 ± 9 years; height: 180 ± 7 cm; weight: 83 ± 6 kg) with a history of complete unilateral ATR, approximately 4 years post-surgery. Using ultrasonography, GM tendon morphology, muscle architecture at rest, and fascicular behavior were assessed during walking at 1.5 m⋅s on a treadmill. Walking patterns were recorded with a motion capture system. The unaffected leg served as control. Lower limbs kinematics were largely similar between legs during walking. Typical features of ATR-related MTU remodeling were observed during the stance sub-phases corresponding to series elastic element (SEE) lengthening (energy storage) and SEE shortening (energy release), with shorter GM fascicles (36 and 36%, respectively) and greater pennation angles (8° and 12°, respectively). However, relative to the optimal fascicle length for force production, fascicles operated at comparable length in both legs. Similarly, when expressed relative to optimal fascicle length, fascicle contraction velocity was not different between sides, except at the time-point of peak series elastic element (SEE) length, where it was 39 ± 49% lower in the affected leg. Concomitantly, fascicles rotation during contraction was greater in the affected leg during the whole stance-phase, and architectural gear ratios (AGR) was larger during SEE lengthening. Under the present testing conditions, former ATR patients had recovered a relatively symmetrical walking gait pattern. Differences in seen AGR seem to accommodate the profound changes in MTU architecture, limiting the required fascicle shortening velocity. Overall, the contractile behavior of the GM fascicles does not restrict length- or velocity-dependent force potentials during this locomotor task.
跟腱断裂（ATR）在损伤多年后仍与功能受限有关。患侧小腿通常会观察到内侧腓肠肌（GM）的结构重塑，这可能会补偿因肌腱变长导致的力量不足。然而，患者在低力量行走步态中似乎仍存在功能受限。为了探究重塑的GM肌-腱单元（MTU）对行走步态施加的潜在限制，我们检查了站立期肌肉束的收缩行为。在一项横断面设计中，我们研究了9名有单侧完全性ATR病史的男性患者（年龄：45±9岁；身高：180±7厘米；体重：83±6千克），手术时间约为4年前。使用超声检查，在跑步机上以1.5米/秒的速度行走时，评估GM肌腱形态、静息时的肌肉结构和肌肉束行为。用运动捕捉系统记录行走模式。未受影响的腿作为对照。行走过程中，双下肢的运动学在很大程度上相似。在与串联弹性元件（SEE）延长（能量储存）和SEE缩短（能量释放）相对应的站立子阶段，观察到了与ATR相关的MTU重塑的典型特征，GM肌肉束较短（分别为36%和36%），羽状角较大（分别为8°和12°）。然而，相对于产生力量的最佳肌肉束长度，双腿的肌肉束在相当的长度下运作。同样，当相对于最佳肌肉束长度表示时，除了在串联弹性元件（SEE）长度峰值的时间点，患侧的肌肉束收缩速度在两侧没有差异，在该时间点患侧比健侧低39±49%。同时，在整个站立期，患侧肌肉束在收缩过程中的旋转更大，并且在SEE延长期间结构传动比（AGR）更大。在当前测试条件下，既往有ATR病史的患者已经恢复了相对对称的行走步态模式。观察到的AGR差异似乎适应了MTU结构的深刻变化，限制了所需的肌肉束缩短速度。总体而言，在这项运动任务中，GM肌肉束的收缩行为不会限制长度或速度依赖性的力量潜力。
