TORSION OF THE LOWER EXTREMITY AND SURFACE ELECTROMYOGRAM MEASUREMENTS.

The relationship between mean rectified electromyogram signals (MREMG) from lower extremity medial and lateral rotator muscle groups and the torsional moment about the longitudinal axis of the lower leg was investigated in the laboratory and in snow skiing experiments. The MREMG was measured by six surface probes positioned over the gluteus maximus, gluteus medius, semitendinosus, biceps femoris, tibialis posterior, and peroneus longus muscles. In the laboratory, torsion was self-induced by each subject. During snow skiing, torsion of the lower extremity resulted from the normal skiing process. Analyses of the laboratory tests data showed excellent correlation between torsion at the foot and MREMG from some rotator muscle groups. Linear regressons of the MREMG from the gluteus medius and peroneus longus with measured torsion predicted the torsion with correlation coefficients as high as 0. 98 and standard deviations as small as 3. 3 N multiplied by (times) m.