2001 Volume 4 Issue 4 Pages 232-242
Viscoelastic properties in muscle-tendon complex (MTC) must be changed by temporary exercise and training. The purpose of the present study was to examine the change of viscoelastic properties in human triceps surae MTC caused by muscle fatigue through isometric endurance exercise. The viscoelastic properties of the human triceps surae by six subjects were assessed using the free vibration method: subjects sat with their forefoot on the edge of a force-plate and support a frame loaded with five weights (0 to 40 kg) on the knee. Oscillations of the triceps surae MTC were initiated with a hand-held hammer by tapping the weight load. Oscillations occur at frequencies of 3 - 6 Hz and are lightly damped. Five measurements were tried for each weight. The viscoelastic properties of MTC itself were estimated by considering ankle moment arm. A curvilinear increase in elasticity (k) was noted with increasing muscle force (f). The elasticity was divided into two parts: muscle (kd) and tendon (ki) elastic coefficients, based on the k-f curve. As an isometric endurance exercise, the subjects were asked to support the weight of 40 kg on their knee as long as possible sitting in the same posture described above. The average duration of isometric exercises was 6.7 (s. d. 4.8) min. The viscoelastic properties were measured before and immediately after the exercises. After the exercise, the total elastic coefficient decreased slightly in low MTC force, while it increased in high force. It can be said that the effect of exercise was different according to MTC force. In other words, tendon elasticity significantly increased after the endurance exercises, although muscle elasticity significantly decreased. On the other hand, the viscosity increased slightly after the exercises.
