Viscoelasticity of the muscle–tendon unit is returned more rapidly than range of motion after stretching

Abstract

The purpose of this study was to clarify the time course of the viscoelasticity of gastrocnemius medialis muscle and tendon after stretching. In 11 male participants, displacement of the myotendinous junction on the gastrocnemius medialis muscle was measured ultrasonographically during the passive dorsiflexion test, in which the ankle was passively dorsiflexed at a speed of 1°/s to the end of the range of motion (ROM). Passive torque, representing resistance to stretch, was also measured using an isokinetic dynamometer. On five different days, passive dorsiflexion tests were performed before and 0, 15, 30, 60 or 90 min after stretching, which consisted of dorsiflexion to end ROM and holding that position for 1 min, five times. As a result, end ROM was significantly increased at 0, 15 and 30 min (P<0.05 each) after stretching as compared with each previous value. Passive torque at end ROM was also significantly increased after stretching. Although the stiffness of the muscle-tendon unit was significantly decreased immediately after stretching (P<0.05), this shift recovered within 15 min. These results showed that the retention time of the effect of stretching on viscoelasticity of the muscle-tendon unit was shorter than the retention time of the effect of stretching on end ROM.

Method and strain rate dependence of Achilles tendon stiffness

“…A range of methods, which are likely to result in different strain rates have been used in the literature to obtain tendon stiffness, including the passive method (Mizuno et al, 2011;Morse et al, 2008), and several variations of the active method (e.g., fast MVC manoeuvres - Kay and Blazevich, 2009;Muraoka et al, 2005or slow, ramped MVC's -Waugh et al, 2012Peltonen et al, 2010;Kubo et al, 2002). Such differences in strain rates could potentially explain the relatively large range of tendon stiffness values reported across these studies.…”

“…The force-stiffness relationship has been shown to be non-linear (Rigby et al, 1959), as at lower tendon stiffness values the un-crimping of collagen fibrils causes significant tendon elongation. As a result, tendon stiffness is greater at high compared to low force levels (Mizuno et al, 2011).…”

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“…Indeed, these parameters remained depressed and did not change further. Mizuno et al [28] presented that decreased stiffness returned to baseline within 15 min. Moreover, they assessed a lower diminution compared to the present study.…”

Acute Changes in Autonomic Nerve Activity during Passive Static Stretching

“…They had not been involved in any resistance training or stretching program before the study. The sample size was calculated on the basis of an α level of 0.05 and a power (1-β) of 0.8, with an estimated 20% difference in ROM before and after of SS using data from a previous study [11]. Their height was 175.0±6.4cm(mean ± standard error: the same below) and body weight was 68.…”

“…The study participants visited the laboratory on three occasions at the same time of day, with at least 48 h between visits; all experimental trials were completed within 3weeks. A full familiarization with the SS protocol and test procedures was provided during the first session, whereas the subsequent two visits were used to complete the following experimental protocol, in a randomized order: 1) control session (no stretching); 2) five sets of 1-min passive plantar flexor SS, as described previously [11,12]. Data were collected during a period of 30-min including these stretching sessions, a period of resting in the sitting position (the knee fully extended) for 15-min before stretching (referred to as "pre" below), and a 5-min period after stretching (referred to as "post" below).…”