Effect of relaxation time on hysteresis of human tendon .

OBJECTIVES

The purpose of this study was to investigate the effect of relaxation time on tendon hysteresis.

METHODS

Subjects exerted isometric plantar flexion torque from rest to maximal voluntary isometric contractions within around 0.5 s, followed by relaxation with six different times (0.3, 0.5, 0.7, 1, 3, and 5 s). During each trial, tendon elongation in the medial gastrocnemius muscle was measured by ultrasonography. The area within the exerted torque-tendon elongation loop, as a percentage of the area beneath the curve during ascending phase, was calculated as tendon hysteresis.

RESULTS

Between the 0.3 and 1 s relaxation time conditions, the hysteresis values were significantly greater for the shorter relaxation time conditions (except between the 0.5 and 0.7 s conditions). In contrast, no significant differences in tendon hysteresis were found between 1 and 5 s of relaxation time conditions. Furthermore, the relationship between relaxation time and tendon hysteresis showed a significantly negative correlation under 1 s or less of relaxation time, but no significant correlation was observed under conditions of 1 s or more.

CONCLUSION

These results suggest that relaxation time greatly affects tendon hysteresis under condition that relaxation time was less than 1 s.