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 (k_d) and tendon (k_i) 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.

Many studies of baseball pitching have been conducted, but few of have focused on the sidearm and underhand pitching styles. To describe kinematic and kinetic characteristics of sidearm and underhand baseball pitching, four professional pitchers (two for sidearm, two for underhand) and a comparison group of thirteen overhand and three-quarter-hand pitchers were videotaped with the use of two high-speed cameras (200 Hz)_. After a small reliability study, the fastest throws that struck the strike was chosen for analyses. An inverse dynamic approach was used to determine joint kinetics of the upper extremity. If both data from a particular group were more than one standard deviation from the comparison mean, then it was assumed that there was a trend towards the data being different from the comparison group. The underhand pitchers bent their trunks to the throwing arm side and the sidearm pitchers kept their trunk relatively erect. The underhand pitchers abducted their shoulders lower than 75 degrees during the arm acceleration phase and the sidearm pitchers kept their shoulder perpendicular to the trunk. Maximum elbow medial forces for the sidehand pitchers and maximum shoulder anterior forces for the underhand pitchers were greater than the comparison group. Maximum shoulder horizontal adduction torques for the underhand pitchers were less than the comparison group. The sidearm pitching and the underhand pitching had different kinematic and kinetic characteristics from the overhand and three-quarter-hand pitching. The knowledge from the previous studies should not be always applied to these pitching styles.