Changes in joint, muscle, and tendon stiffness following repeated hopping exercise

This is the first study to demonstrate that active muscle stiffness with and without the stretch reflex and joint stiffness significantly decreased after repeated stretch ‐shortening cycle exercises, although tendon stiffness measured during ramp and ballistic contractions and neuromuscular activities during the measurement of joint stiffness did not. These results suggested that decline in joint stiffness was related to changes in the active muscle stiffness, but not those in tendon properties or neuromuscular activities. AbstractThe purpose of this study was to elucidate the mechanisms of decline in joint stiffness after repeated stretch ‐shortening cycle exercises according to changes in both muscle‐tendon properties and neuromuscular activities. Eleven males performed fatigue task (5 sets of 50 hopping). Ankle joint stiffness and electromyographic activities (mEMG) of plantar flexor and tibial anterior muscles during drop jump were measured before and after fatigue task. Active muscle stiffness with (100 deg·sec−1) and without (250  deg·sec−1) stretch reflex were calculated according to changes in estimated muscle force and fascicle length during fast stretching after submaximal isometric contractions. Tendon stiffness was measured during ramp and ballistic contractions. After fatigue task, joint stiffness significantly decreased by 20.7 %, whereas mEMG of measured muscles during drop jump did not. After fatigue task, active muscle stiffness with and without...

Source: Physiological Reports - October 11, 2019 Category: Physiology Authors: Keitaro Kubo, Toshihiro Ikebukuro Tags: Original Research Source Type: research