Neuromuscular behaviour of the triceps surae muscle-tendon complex during running and jumping.

The present study examined the behaviour of the Achilles tendon (AT) - triceps surae (TS) muscle complex during running and long jump take-off. High AT forces were measured in the push-off phase in running even with very low EMG activity. In the long jump, high rate of stiffness development was a characteristic of the braking phase of the jump. The results suggest that high and well-coordinated activation patterns of the leg extensor muscles during the preactivation and eccentric phases together with high stretching velocities of muscle-tendon complex provide basis for appropriate tendomuscular stiffness. This together with high force at the end of the eccentric phase enables an effective push-off (concentric) phase.