Differences of activation pattern and damage in elbow flexor muscle after isokinetic eccentric contractions

BACKGROUND: Eccentric contractions (ECC)-induced muscle damage and activation pattern are not fully understood. OBJECTIVE: To investigate the activation level and damage in each muscle and site after ECC. METHODS: Eleven men performed 30 isokinetic ECC of the elbow flexors. Maximal voluntary isometric contraction (MVC) torque, range of motion of the elbow joint (ROM), delayed onset muscle soreness (DOMS), transverse relaxation time (T2), and cross-sectional area (CSA) were measured immediately before, immediately after, and 1, 3, 5 days after ECC. RESULTS: MVC and ROM significantly decreased while DOMS significantly increased until 3 days after ECC. The CSA of the brachialis significantly increased after ECC. The T2 in biceps brachii and middle and distal brachialis increased significantly at post (p < 0.01) day 1 (middle; p < 0.01, distal; biceps brachii, p < 0.05, brachialis, p < 0.01), and day 3 (middle; p < 0.01, distal; biceps brachii, p < 0.05, brachialis, p < 0.01). In addition, after 5 days only the distal brachialis has shown a significant increase (p < 0.01). CONCLUSIONS: Following maximal ECC the activation pattern and muscle damage differ among the elbow flexors depending upon the individual muscle and site of recording.