REPRODUCIBILITY OF ELECTROMYOGRAPHIC RECORDINGS OF SUBMAXIMAL CONCENTRIC AND ECCENTRIC MUSCLE CONTRACTIONS IN HUMANS

Objectives: to determine the intratester and intertester reliability o f measures of electromyographic activity (EMG) of submaximal concentri c and eccentric contractions and to compare the reliability of normali zed and non-normalized measures of EMG. There were 10 subjects, of 22- 33 years old. Methods: Subjects performed submaximal concentric and ec centric contractions at 60 degrees/s, and maximal isometric contractio ns (MIC) of their knee extensors. The target power of the submaximal c ontractions was 90% +/- 10% of the subject's maximal concentric power. EMG was recorded via bipolar surface electrodes from 3 of the quadric eps femoris muscles. The rmsEMG for submaximal contractions that were within the target power range were determined. The rmsEMG for the subm aximal contractions were normalized to the rmsEMG of the maximal isome tric contractions. Intraclass correlation coefficients (ICC version 1. 1) were calculated to determine intratester and intertester reliabilit y. Results: For non-normalized rmsEMG, ICC values for intratester reli ability ranged from 0.62 to 0.91 for concentric and from 0.84 to 0.97 for eccentric contractions. ICC values for intertester reliability ran ged from 0.66 to 0.96 for concentric and 0.78 to 0.90 for eccentric co ntractions. Conclusions: Non-normalized rmsEMG of submaximal concentri c and eccentric isokinetic contractions were found to be reliable. Nor malization did not lead to consistently improved reliability. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.