Mechanomyography and electromyography force relationships during concentric, isometric and eccentric contractions

The purpose of this study was to investigate systematically if complementar y knowledge could be obtained from the recordings of electromyography (EMG) and mechanomyography (MMG) signals. EMG and MMG activities were recorded f rom the first dorsal interosseous muscle during slow concentric, isometric, and eccentric contraction at 0, 25, 50, 75 and 100% of the maximal volunta ry contraction (MVC). The combination of the EMG and MMG recordings during voluntary concentric-isometric-eccentric contraction showed significant dif ferent non-linear EMG/force and MMG/force relationships (P<0.001). The EMG root mean square (rms) values increased significantly from 0 to 50% MVC dur ing concentric and isometric contraction and up to 75% MVC during eccentric contraction (P<0.05). The MMG rms values increased significantly from 0 to 50% MVC during concentric contraction (P<0.05). The non-linear relationshi ps depended mainly on the type and the level of contraction together with t he angular velocity. Furthermore, the type of contraction, the contraction level, and the angular velocity influenced the electromechanical efficiency evaluated as the MMC to EMG ratio (P<0.05). These results highlight that E MG and MMG provide complementary information about the electrical and mecha nical activity of the muscle. Different activation strategies seem to be us ed during graded isometric and anisometric contraction. (C) 2001 Elsevier S cience Ltd. All rights reserved.