Ust 5710

Ultrasonographic measurement (SSD-3500; Aloka, Tokyo, Japan) was performed simultaneously during the above three trials to examine whether changes in architectural characteristics (i.e. fascicle length and pennation angle) were related to the SSC effect. A linear array probe (7.5 MHz, field of view: 6 × 6 cm, UST-5710; Aloka, Tokyo, Japan) was used to obtain images of the belly of the medial gastrocnemius muscle. The ultrasonographic probe was fixed onto the skin by using underwrap and surgical tape. Fascicle length was defined as the distance between the intersection of the superficial aponeurosis and fascicle and the intersection of the deep aponeurosis and fascicle, while pennation angle was defined as the acute angle formed by the fascicle and deep aponeurosis. Sampling frequency of ultrasonography was 30 Hz. Synchronization of joint torque and joint angle was done by inserting a pulse into the ultrasonographic recording machine. Acquired images were analysed by ImageJ 1.47v software (National Institute of Health, Bethesda, MD, USA).

Ultrasonography (SSD-3500; Aloka, Tokyo, Japan) with a linear array probe (UST-5710; Aloka, Tokyo, Japan) was used to obtain images of the muscle belly of the medial gastrocnemius (Fig. 4) with a sampling frequency of 30 Hz. Muscle fascicle length and pennation angle during each twitch contraction were obtained. Muscle fascicle length was defined as the distance between the intersection composed of the superficial aponeurosis and muscle fascicle, and the intersection composed of the deep aponeurosis and muscle fascicle. Pennation angle was defined as the angle between the muscle fascicle and deep aponeurosis. The magnitude of muscle fascicle shortening during twitch contractions (i.e., muscle fascicle length at rest minus muscle fascicle length at the moment when peak twitch torque occurred) was calculated. This value was corrected by considering the pennation angle obtained at the moment when peak twitch torque occurred (i.e., muscle fascicle length × cos θ). This muscle fascicle shortening is considered to correspond to the tendon elongation when the joint angle (i.e., muscle-tendon complex length) is constant^{5 (link)–8 (link)}. In our previous study, coefficient of variations of fascicle length and pennation angle were confirmed to be 1.1% and 1.6%, respectively, while the intraclass correlation of those were confirmed to be 0.993 and 0.989, respectively²⁴ .