In Vivo Elastic Properties of Human Tendon Structures in Lower Limb

Abstract

The present study was conducted to evaluate the elastic properties of human tendon structures and their influences on human movements, and to investigate the effects of resistance training on tendon properties. During isometric contraction, the elongations of tendon structures in knee extensors and plantar flexors were measured by means of real-time ultrasonography. The resulting tendon force and elongation relationship was non-linear in form, as previously reported on animal and human cadaver tendons in vitro. The estimated Young's modulus, i.e., the slope of the stress -strain curve, tended to be lower than the previously reported values. In human movements, the elastic properties of tendon structures had a favorable effects on stretch-shortening cycle exercises, possibly because of improved storage and release of elastic energy. Furthermore, the adaptation of the tendon structures to physical training varies with the combinations of intensity, contraction time during exercise as previously observed in the animal experiments. Furthermore, the elastic properties of human tendon structures could be new indices of physical resources in vivo.

Influences of tendon stiffness, joint stiffness, and electromyographic activity on jump performances using single joint

“…5). We also previously reported that tendon stiffness in knee extensors was inversely correlated with the relative difference in jump height between vertical jumps performed with and without countermovement (Kubo et al 1999;Kubo 2005). However, according to the correlation coefficient of r = -0.471 for CMJ and r = -0.502 for DJ between the two parameters, the tendon stiffness only accounted for 22-25% of the variance in the pre-stretch augmentation.…”

“…However, the previous studies (Kubo et al 1999;Kubo 2005;Bojsen-Moller et al 2005) included some flaws. First, jump tests taken in the previous studies consisted of multi-joint movements, and so it was difficult to specify the muscles mainly acting to perform the task.…”

“…It is well known that if an activated muscle is stretched prior to shortening, its performance is enhanced during the concentric phase (Alexander and Bennet-Clark 1977;Bosco et al 1982;Fukunaga et al 2001;Kawakami et al 2002;Kubo et al 1999;Kubo 2005;Svantesson and Grimby 1995). The enhancement of performance during stretch-shortening cycle exercise may be attributed to the combined effects of utilization of elastic energy and stretch reflex potentiation of muscle activity (e.g., Bosco et al 1982).…”

“…Second, the previous studies (Kubo et al 1999;Kubo 2005;Bojsen-Moller et al 2005) did not examine the effects of other factors except for tendon elasticity during stretch-shortening cycle exercises, e.g., the activation level of muscles. Kilani et al (1989) indicated that the myoelectric responses accounted for up to 85% of the increase in jump height following a countermovement.…”

Does Stretching Have Long-Term Effects on Muscle Performance? A Clinical Commentary

“…A previous investigation [34] has shown that the association of resistance and flexibility training decreases MTU hysteresis more than resistance training alone. Hysteresis is defined as the energy lost as heat during stretching of viscoelastic materials [47]. A decrease in hysteresis following chronic stretching provides an indication that adequate flexibility may improve performance in dynamic activities.…”