Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, UK.
Alder Hey Children's NHS Foundation Trust, Liverpool, UK.
J Anat. 2021 Oct;239(4):839-846. doi: 10.1111/joa.13464. Epub 2021 Jun 9.
Children who idiopathically toe-walk (ITW) habitually operate at greater plantarflexion angles and thus, at shorter muscle-tendon unit (MTU) lengths than typically developing (TD) children. Therefore, it is often assumed that habitual use of the gastrocnemius muscle in this way will cause remodelling of the muscle-tendon architecture compared to TD children. However, the gastrocnemius muscle architecture of children who ITW has never been measured. It is essential that we gain a better understanding of these muscle-tendon properties, to ensure that appropriate clinical interventions can be provided for these children. Five children who ITW (age 8 ± 2 years) and 14 TD children (age 10 ± 2 years) participated in this study. Ultrasound was combined with isokinetic dynamometry and surface electromyography, to measure muscle architecture at common positions and passive lengthening properties of the gastrocnemius muscle and tendon across full range of motion. Regardless of which common condition groups were compared under, both the absolute and normalised to MTU muscle belly and fascicle lengths were always longer, and the Achilles tendon length was always shorter in children who ITW than TD children (p < 0.05; large effect sizes). The passive lengthening properties of the muscle and tendon were not different between groups (p > 0.05); however, passive joint stiffness was greater in children who ITW at maximum dorsiflexion (p = 0.001) and at a joint moment common to all participants (p = 0.029). Consequently, the findings of this pilot study indicate a remodelling of the relative MTU that does not support the concept that children who ITW commonly experience muscle shortening. Therefore, greater consideration of the muscle and tendon properties are required when prescribing clinical interventions that aim to lengthen the MTU, and treatments may be better targeted at the Achilles tendon in children who ITW.
习惯性踮脚走（ITW）的儿童习惯性地以更大的跖屈角度活动，因此，与正常发育（TD）的儿童相比，肌肉-肌腱单位（MTU）长度更短。因此，人们通常认为，习惯性地以这种方式使用腓肠肌会导致与 TD 儿童相比，肌肉-肌腱结构发生重塑。然而，从未测量过 ITW 儿童的腓肠肌肌肉结构。我们必须更好地了解这些肌肉-肌腱特性，以确保为这些儿童提供适当的临床干预。本研究纳入了 5 名 ITW 儿童（年龄 8±2 岁）和 14 名 TD 儿童（年龄 10±2 岁）。超声结合等速测力和表面肌电图，测量了常见位置的肌肉结构以及整个运动范围内的腓肠肌和肌腱的被动伸长特性。无论比较哪种常见的条件组，ITW 儿童的肌肉腹和肌束的绝对长度和标准化到 MTU 的长度总是更长，跟腱长度总是更短（p<0.05；大效应量）。肌肉和肌腱的被动伸长特性在组间无差异（p>0.05）；然而，在最大背屈时 ITW 儿童的被动关节刚度更大（p=0.001），在所有参与者共同的关节力矩时也更大（p=0.029）。因此，这项初步研究的结果表明，相对 MTU 的重塑并不支持 ITW 儿童通常经历肌肉缩短的概念。因此，在为旨在延长 MTU 的临床干预措施开处方时，需要更全面地考虑肌肉和肌腱特性，并且在 ITW 儿童中，治疗可能更针对跟腱。
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