Electromyographic activity of selected trunk muscles in subjects with and without hemiparesis during therapeutic exercise.

The purpose of this study was to evaluate the trunk muscles activity of hemiparetic and control subjects during selected therapeutic exercises with surface electromyography (sEMG). The sEMG evaluation included 12 subjects presenting hemiparesis after having suffered a unilateral stroke and 12 apparently healthy subjects. A 16-channel sEMG system was used; data were band pass filtered from 20 to 450Hz. The signal was normalized through reference voluntary contraction (RVC) and presented in percentage. The exercises used in the evaluations were trunk flexion and trunk extension. Rectus abdominis presented greater activation on the paretic side of the experimental group than on the corresponding side of the control group (P=0.035) (Cohen's d¯=0.94). During leg elevation, the non-paretic obliquus externus abdominis showed greater activation than in other exercises (P=0.019) (Cohen's d¯=0.75). No inter-group differences were found for either erectus spinae activity or contraction onset. Experimental group subjects showed muscle activity alterations, principally in the rectus abdominis, indicating the occurrence of compensatory strategies.