Abstract
Achilles tendon length has been measured using a straight‐line model. However, this model is associated with a greater measurement error compared with a curved‐line model. Therefore, we examined the influence of neglecting the curved path of the Achilles tendon on its length change at various ranges of motion. Ten male subjects participated in this study. First, the location of the Achilles tendon was confirmed by using ultrasonography, and markers were attached on the skin over the Achilles tendon path. Then, the three‐dimensional coordinates of each marker at dorsiflexion (DF) 15°, plantarflexion (PF) 0°, PF15°, and PF30° were obtained. Achilles tendon length in the curved‐line model was calculated as the sum of the distances among each marker. On the other hand, Achilles tendon length in the straight‐line model was calculated as the straight distance between the two most proximal and distal markers projected onto the sagittal plane. The difference of the Achilles tendon length change between curved‐line and straight‐line models was calculated by subtracting the Achilles tendon length change obtained in curved‐line model from that obtained in straight‐line model with three different ranges of motion (i.e., PF0°, PF15°, and PF30° from DF15°, respectively). As a result, the difference in Achilles tendon length change between the two models increased significantly as the range of motion increased. In conclusion, neglecting the curved path of the Achilles tendon induces substantial overestimation of its length change when the extent of ankle joint angle change is large.
Highlights
The Achilles tendon is believed to play an important role in dynamic movements, such as walking and jumping, due to its ability to store and release elastic energy during these movements (Fukashiro et al 1995; Magnusson et al 2008)
This study examined the influence of neglecting the curved path of the Achilles tendon on its length change at various ranges of motion
In 2D-straight and 3D-straight, which ignored the tendon’s curved path (Fig. 3, bar 3 and 4), Achilles tendon length change was larger than that obtained in 3D-curve and 2D-curve, which considered the tendon’s curved path (Fig. 3, bar 1 and 2). These results show that if the curved path of the Achilles tendon is not considered, the magnitude of Achilles tendon length change is overestimated
Summary
The Achilles tendon is believed to play an important role in dynamic movements, such as walking and jumping, due to its ability to store and release elastic energy during these movements (Fukashiro et al 1995; Magnusson et al 2008). Many studies have evaluated Achilles tendon length change during dynamic movements. To examine the effect of Achilles tendon length change on the aforementioned human movements, accurate measurement is required. Because direct measurement of Achilles tendon length change is difficult, especially during dynamic movements, indirect a 2014 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of the American Physiological Society and The Physiological Society.
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