Exercise induced muscle damage and recovery assessed by means of linear and non-linear sEMG analysis and ultrasonography

This study was aimed at investigating the time-course and recovery from ecc entric (EC) exercise induced muscle damage by means of surface electromyogr aphy (sEMG), ultrasonography (US), and blood enzymes. Five subjects (EC Gro up) performed two bouts of 35 EC maximum contractions with the biceps brach ii of their non dominant arm. five subjects were tested without performing EC (Control Group: CNT). The maximal isometric force (MVC) was measured. Fo rce and sEMG signals were recorded during 80% MVC isometric contractions. I n EC and CNT subjects US assessment on non-dominant biceps brachii was perf ormed: creatin kinase (CK) and lactic dehydrogenasis (LDH) plasma levels we re also assessed. Force. sEMG and CK-LDH,measurements were performed before EC and after it periodically for 4 weeks. The sEMG was analysed in time an d frequency domains; a non-Linear analysis (Lyapunov 1st exponent, L1) of s EMG was also performed. After EC, the MVC was reduced by 40% on average wit h respect to the pre-EC values. A significant decrease in the initial frequ ency content, and in the MDF and L1 decay (13-42% less than the pre-EC valu es, respectively) was also observed. The sEMG amplitude (Root Mean Square, RMS) was unchanged after EC. The US revealed an increase in muscle belly th ickness and in local muscle blood Row after EC. A complete recovery of all the considered parameters was achieved in two weeks. In conclusion sEMG ana lysis was confirmed as an early indicator of muscle damage. Muscle recovery from damage is followed by both sEMG and US and this may have useful clini cal implications. Non linear analysis (L1) was revealed to be sensitive to early sEMG modifications induced by EC as well as able to follow the post E C changes in the sEMG. (C) 2001 Elsevier Science Ltd. All rights reserved.