Interaction between gastrocnemius medialis fascicle and Achilles tendon compliance: a new insight on the quick-release method

Abstract

The insufficient temporal resolution of imaging devices has made the analysis of very fast movements, such as those required to measure active muscle-tendon unit stiffness, difficult. Thus the relative contributions of tendon, aponeurosis, and fascicle to muscle-tendon unit compliance remain to be determined. The present study analyzed the dynamic interactions of fascicle, tendon, and aponeurosis in human gastrocnemius medialis during the first milliseconds of an ankle quick-release movement, using high-frame-rate ultrasonography (2,000 frames/s). Nine subjects performed the tests in random order at six levels of maximal voluntary contraction (MVC) (30% to 80% of MVC). These tests were carried out with the ultrasound probe placed on the muscle belly and on the myotendinous junction. Tendon, muscle fascicle, and aponeurosis length changes were quantified in relation to shortening of the muscle-tendon unit during the first few milliseconds following the release. The tendon was the main contributor (around 72%) to the shortening of the muscle-tendon unit, whereas the muscle fascicle and aponeurosis contributions were 18% and 10%, respectively. Because these structures can be considered in series, the quantified contributions can be regarded as relative contributions to muscle-tendon compliance. These contributions were not modified with the level of MVC or the time range used for the analysis between 10 and 25 ms. The constant contribution of tendon, muscle fascicle, and aponeurosis to muscle-tendon unit compliance may help to simplify the mechanism of compliance regulation and to maintain the important role of tendons in enhancing work output and movement efficiency.

Muscle fascicle shortening behaviour of vastus lateralis during a maximal force–velocity test

“…After each extension, the knee was passively placed in starting position. The previous studies showed higher maximal joint velocity during unloaded plantar flexions performed with preactivation (1325° s −1 , Farcy et al 2014) compared to without pre-activation (701° s −1 , Hauraix et al 2015). However, the maximal fascicle shortening velocity was much higher without pre-activation (23.2 cm s −1 compared to 34.7 cm s −1 ).…”

In vivo maximal fascicle-shortening velocity during plantar flexion in humans

“…We deliberately chose to perform plantar-flexion contractions without preactivation so as not to be in a "quick-release" condition. Indeed, although such an experimental setup should induce an increase in angular velocity, quick-release movements largely increase the contribution of tendinous structures (17) and should notably alter the fascicle-tendon interaction (and length) at the beginning of the contraction. Consequently, these authors reported a lower maximal gastrocnemius medialis fascicle-short-ening velocity in the quick-release condition than in the present study in NLc [4.6 L O /s (17)].…”

“…The torque measured by the isokinetic dynamometer was corrected for inertia and gravity to obtain external torque at the ankle joint. On the specific ergometer system (light-load isoinertial conditions), the moment of inertia (i.e., foot, footplate, and additional loads) was estimated using quick-release protocol (17). Torque was calculated as the moment of inertia multiplied by the acceleration of the ankle angle and corrected for weight (foot and additional loads).…”

“…Although measurement of fascicle-shortening velocity is classically performed using ultrasound (13), the sampling frequency of conventional devices (i.e., the number of images per second, typically 30 -170 Hz) limits the investigations to relatively slow motion, far from the maximal velocities reached during human movements. In this context, ultrafast ultrasound (14, 55) could be used to overcome this limitation and analyze very fast movements (17,29,47). Using this technique, we measured fascicle-shortening velocity during maximal isokinetic plantar flexions performed at various submaximal preset angular velocities, from 30°/s up to 330°/s (29).…”

Muscle force loss and soreness subsequent to maximal eccentric contractions depend on the amount of fascicle strain in vivo

“…1c). When the fascicle was not fully visible, its length (L F ) was interpolated as the length of the straight line between the superficial and deep aponeurosis (Hauraix et al 2013, Farcy et al 2014. The angle between the fascicle and the deep aponeurosis corresponded to the pennation angle.…”