Slack length of gastrocnemius medialis and Achilles tendon occurs at different ankle angles

Reliable Protocol for Shear Wave Elastography of Lower Limb Muscles at Rest and During Passive Stretching

“…This result was expected, given the mechanical nonlinear behaviour of the muscle, and is in accordance with previous studies by Maïsetti et al (2012) and Hug et al (2013), who have found an increase of muscle shear modulus during passive stretching once the threshold of the slack length was passed. Soleus muscle is not involved in knee motion, the non-significant difference confirmed that altough the ankle joint angle was not strictly controlled, muscle stiffness varied little between positions.…”

“…Moreover, subject position affects the measurement: an increase of the shear modulus was observed when muscle is passively stretched, both in vitro (Shinohara et al, 2010;Maïsetti et al, 2012;Koo et al, 2013) and ex vivo (Eby et al, 2013). Maïsetti et al (2012) and Hug et al (2013) determined in vivo the slack length of the muscle, corresponding to a range of motion in which the muscle does not produce any passive force and in which shear modulus was constant.…”

Muscle-specific acute changes in passive stiffness of human triceps surae after stretching

“…The ankle joint angle was passively dorsiflexed from 50° plantar flexion [neutral position (i.e., the sole of the foot at right angles to the tibia axis) defined as 0°, with larger values for dorsiflexion] to the end ROM which was defined as the angle that the subjects felt pain, at an angular velocity of 1°/s. The very slow angular velocity was used to obtain a better resolution for the muscle stiffness via ultrasound shear wave elastography and to avoid or minimize the stretch reflex (Hirata et al 2015;Hug et al 2013;Morse et al 2008), which could stiffen the muscles. The angular displacement of the ankle joint was measured with an electronic goniometer (SG110/A, Biometrics, UK) fixed to the ankle joint with double-sided adhesive tape.…”

Evidence for intermuscle difference in slack angle in human triceps surae

“…However, this does not necessarily hold for other muscle groups. Hug et al (2013) have reported that slack angle for MG was less plantarflexed position than that for the Achilles tendon in the knee extended position. This tempts us to hypothesize that the slack angle of the soleus (Sol) is more plantarflexed than that of MG. By the use of ultrasound shear wave Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/jbiomech www.JBiomech.com elastography, therefore, the purpose of the present study was to clarify whether the slack angle differs among each muscle of the human triceps surae at the knee extended position.…”