Harkness-Armstrong Carla, Debelle Héloïse A, Maganaris Constantinos N, Walton Roger, Wright David M, Bass Alfie, Baltzopoulos Vasilios, O'Brien Thomas D
Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, United Kingdom.
Alder Hey Children's NHS Foundation Trust, Liverpool, United Kingdom.
Front Physiol. 2020 May 19;11:407. doi: 10.3389/fphys.2020.00407. eCollection 2020.
To study the causes of locomotor dysfunction, estimate muscle forces, or understand the influence of altered sarcomere and muscle properties and behaviours on whole body function, it is necessary to examine the leverage with which contractile forces operate. At the ankle joint, current methods to quantify this leverage for the plantarflexors do not account for curvature of the Achilles tendon, and so may not be appropriate when studying equinus gait. Thus, novel methodologies need to be developed and implemented to quantify the Achilles tendon moment arm length during locomotion. Plantarflexor internal moment arm length and effective mechanical advantage of 11 typically developed young adults were calculated throughout stance, while heel-toe walking and voluntarily toe-walking on an instrumented treadmill. Achilles tendon moment arm was defined in two-ways: (1) assuming a straight tendon, defined between the gastrocnemius medialis myotendinous junction and Achilles tendon insertion point, and (2) accounting for tendon curvature, by tracking the initial path of the Achilles tendon from the calcaneal insertion. When accounting for tendon curvature, Achilles tendon moment arm length and plantarflexor effective mechanical advantage did not differ between walking conditions ( > 0.05). In contrast, when assuming a straight tendon, Achilles tendon moment arm length ( = 0.043) and plantarflexor effective mechanical advantage ( = 0.007) were significantly greater when voluntary toe-walking than heel-toe walking in late stance. Assuming a straight Achilles tendon led to a greater Achilles tendon moment arm length and plantarflexor effective mechanical advantage during late stance, compared to accounting for tendon curvature. Consequently, plantarflexor muscle force would appear smaller when assuming a straight tendon. This could lead to erroneous interpretations of muscular function and fascicle force-length-velocity behaviour , and potentially inappropriate and ineffective clinical interventions for equinus gait.
为了研究运动功能障碍的原因、估计肌肉力量，或了解肌节和肌肉特性及行为改变对全身功能的影响，有必要研究收缩力起作用的杠杆作用。在踝关节处，目前用于量化跖屈肌这种杠杆作用的方法没有考虑跟腱的曲率，因此在研究马蹄内翻足步态时可能不合适。因此，需要开发和实施新的方法来量化运动过程中跟腱力臂长度。在配备仪器的跑步机上进行足跟到足尖行走和自愿足尖行走时，计算了11名发育正常的年轻成年人在整个站立期的跖屈肌内力矩臂长度和有效机械优势。跟腱力矩臂通过两种方式定义：(1) 假设跟腱是直的，定义在内侧腓肠肌肌腱结合处和跟腱插入点之间；(2) 通过跟踪跟腱从跟骨插入点的初始路径来考虑肌腱曲率。考虑肌腱曲率时，行走条件之间的跟腱力矩臂长度和跖屈肌有效机械优势没有差异（>0.05）。相比之下，假设跟腱是直的时，在站立后期自愿足尖行走时的跟腱力矩臂长度（=0.043）和跖屈肌有效机械优势（=0.007）显著大于足跟到足尖行走时。与考虑肌腱曲率相比，假设跟腱是直的会导致站立后期跟腱力矩臂长度和跖屈肌有效机械优势更大。因此，假设跟腱是直的时，跖屈肌力量看起来会更小。这可能导致对肌肉功能和肌束力-长度-速度行为的错误解释，并可能导致对马蹄内翻足步态的不适当和无效的临床干预。
