Influence of different knee and ankle ranges of motion on the elasticity of triceps surae muscles, Achilles tendon, and plantar fascia

Abstract

Stiffness is a valuable indicator of the functional capabilities of muscle-tendon-fascia. Twenty healthy subjects participated in this study in which the passive elastic properties of the medial gastrocnemius (MG), lateral gastrocnemius (LG), soleus muscles (SOL), Achilles tendon (AT, at 0 cm, 3 cm and 6 cm proximal to the calcaneus tubercle, corresponding to AT0cm, AT3cm and AT6cm, respectively) and plantar fascia (PF) were quantified when their knee was fully extended or flexed to 90° using shear wave elastography at 25° of dorsiflexion (DF25°), 0° (neutral position) of flexion, and 50° of plantar flexion (PF50°) of the ankle joint. The stiffnesses of the AT, MG, LG, SOL and the fascia with the knee fully extended were significantly higher than those with the knee flexed to 90° (p < 0.05), while the stiffness of the PF showed the opposite relationship (p < 0.05). When the knee was fully extended, the stiffness was higher in the LG than in the MG at PF50° and 0° (p < 0.01), and it was higher in the MG than in the LG at DF25° (p = 0.009). Nevertheless, regardless of the knee angle, the stiffness decreased from AT3cm > AT0cm > AT6cm at PF50° and 0° (p < 0.001), while the stiffness decreased from AT0cm > AT3cm > AT6cm at DF25°. Regardless of the knee and ankle angles, the stiffness of the PF increased in a proximal-to-distal direction (p < 0.001). These insights can be used to gain a more intuitive understanding of the relationships between the elastic properties of the muscle-tendon unit and its function. Achilles tendon (AT) injuries and plantar fasciitis can cause chronic pain and impairment 1. In the clinic, the type of treatment administered depends in part on the region and intensity of pain. For example, eccentric exercises are more effective in the treatment of mid-substance tendinopathy than in the treatment of insertional tendinopathy 1. However, because of the complexity of the anatomy and mechanics of the AT and plantar fascia (PF), it can be challenging to identify the region and severity of the damage. In terms of anatomy, the AT, which is the conjoined tendon of the medial gastrocnemius (MG), the lateral gastrocnemius (LG), and the soleus (SOL), is an important bridge for walking, running and jumping in daily life, and each of the contributing muscles exhibit unique structural features 2,3. The twisted structure of the AT is formed by the MG tendons, LG tendons and SOL tendons. These muscle tendons rotate as they descend but do not run parallel to each other 4. In addition, the superficial layer of the AT is formed by the MG tendons, while the deep layer consists of the LG tendons and SOL tendons 5. Furthermore, the LG is shorter and smaller than the MG, so the MG and LG differ in terms of muscle strength and their contribution to the AT 6. In other words, these regional structural features (including those of the MG, LG, SOL, AT and PF) have great inherent variability, which may affect the position and severity of damage in an individual 6. Therefore, it is necessary to further understand the relati...

Effect of prolonged sitting immobility on shear wave velocity of the lower leg muscles in healthy adults: A proof-of-concept study

“…The subject was seated in a reclining chair and maintained 20 degrees of flexion at the ankle joint, 70 degrees of flexion at the knee joint, and 80 degrees of flexion at the hip joint as measured by a goniometer. In this limb position, the ankle is more flexed than the slack angle, which relaxes the triceps surae muscle [6][7][8]. In this limb position, the ankle joint was flexed for the tibialis anterior muscle to keep slightly elongated.…”

“…An attempt to estimate the resting muscle tension during passive motion of the ankle and knee joints was made mainly in the medial and lateral gastrocnemius and soleus muscles, where the slack angle was determined. The elastic modulus was increased by the muscle elongation, in which the muscle was stretched from the slack length [6][7][8].…”

“…On the contrary, if the density of muscles is not uniform, in case of measurement along transverse or oblique muscle fiber direction, it is expressed in terms of the anisotropic modulus (E = ρVs 2 ) [2,7]. In researches of the shear wave velocity in the leg muscles at a resting state (ankle position around the slack angle without muscle contraction), the muscle tissue was measured regarding as the isotropic modulus (E = 3ρVs 2 ) [2,5,[7][8][9].…”

Elasticity of the Achilles Tendon in Individuals With and Without Plantar Fasciitis: A Shear Wave Elastography Study

“…This may be related to the different activity patterns and exercise intensity between the PF group and healthy group. According to previous studies, the more activity or exercise intensity, the greater the stiffness of AT (Engkananuwat et al, 2018;Schneider et al, 2018;Zhou et al, 2019a,b;Liu et al, 2020;Siriphorn and Eksakulkla, 2020).…”

“…Reduction of the AT force may decrease the plantar fascia load (Chen et al, 2015). Moreover, previous studies have demonstrated that stretching can decrease tendon stiffness (Zhou et al, 2019a,b;Liu et al, 2020). Therefore, lengthening or tension relief of the AT, especially in participants with tight AT, may be beneficial in terms of plantar fascia stress relief (Cheng et al, 2008).…”