Effect of eccentric training on the plantar flexor muscle-tendon tissue properties.

PURPOSE: It has been shown that eccentric training can be effective in the rehabilitation of patients with Achilles tendonopathy. The mechanism behind these results is not clear. However, there is evidence that tendons are able to respond to repeated forces by altering their structure and composition, and, thus, their mechanical properties change. In this regard, the objective of the present study was to investigate whether eccentric training affects the mechanical properties of the plantar flexor's muscle-tendon tissue properties. METHODS: Seventy-four healthy subjects were randomized into two groups: an eccentric training group and a control group. The eccentric training group performed a 6-wk eccentric training program for the calf muscles. Before and after this period, all subjects were evaluated for dorsiflexion range of motion using universal goniometry, passive resistive torque of the plantar flexors, and stiffness of the Achilles tendon. Passive resistive torque was measured during ankle dorsiflexion on an isokinetic dynamometer. Stiffness of the Achilles tendon was assessed using a dynamometer, in combination with ultrasonography. RESULTS: The results of the study reveal that the dorsiflexion range of motion was significantly increased only in the eccentric training group. The eccentric heel drop program also resulted in a significant decrease of the passive resistive torque of the plantar flexors (from 16.423 +/- 0.827 to 12.651 +/- 0.617 N.m). The stiffness of the Achilles tendon did not change significantly as a result of training. CONCLUSION: These findings provide evidence that an eccentric training program results in changes to some of the mechanical properties of the plantar flexor muscles. These changes were thought to be associated with modifications to structure rather than to stretch tolerance.

Effect of static and ballistic stretching on the muscle-tendon tissue properties.

PURPOSE: Many studies have been undertaken to define the effects of static and ballistic stretching. However, most researchers have focused their attention on joint range-of-motion measures. The objective of the present study was to investigate whether static- and ballistic-stretching programs had different effects on passive resistive torque measured during isokinetic passive motion of the ankle joint and tendon stiffness measured by ultrasound imaging. METHODS: Eighty-one healthy subjects were randomized into three groups: a static-stretch group, a ballistic-stretch group, and a control group. Both stretching groups performed a 6-wk stretching program for the calf muscles. Before and after this period, all subjects were evaluated for ankle range of motion, passive resistive torque of the plantar flexors, and the stiffness of the Achilles tendon. RESULTS: The results of the study reveal that the dorsiflexion range of motion was increased significantly in all groups. Static stretching resulted in a significant decrease of the passive resistive torque, but there was no change in Achilles tendon stiffness. In contrast, ballistic stretching had no significant effect on the passive resistive torque of the plantar flexors. However, a significant decrease in stiffness of the Achilles tendon was observed in the ballistic-stretch group. CONCLUSION: These findings provide evidence that static and ballistic stretching have different effects on passive resistive torque and tendon stiffness, and both types of stretching should be considered for training and rehabilitation programs.