Electromyographic activity of voluntarily activated trunk flexor and extensor muscles in post-stroke hemiparetic subjects

Abstract

Objective: To study the EMG activity of selected trunk muscles during self-initiated voluntary flexion and extension of the trunk in post-stroke hemiparetic subjects, and to compare measurement results to corresponding findings in control subjects.

Methods: Using a sample of 50 patients and 30 control subjects, bilateral EMG activity of the rectus abdominis (RA) and external oblique (EO) muscles was studied during direct trunk flexion, and activity of the lumbar erector spinae (ES) and latissimus dorsi (LD) was studied during straight trunk extension. Variables of timing, magnitude, and temporal synchronization between muscle activity on the paretic and non-paretic sides of the body in the patient group were compared with the same measurements taken from the left and right sides of the body in the control group.

Results: Activity of the RA and LD muscles on the affected side of the body was reduced and delayed relative to the unaffected side in the patients and relative to the control subjects. Some deterioration was also observed in the function of the EO muscle, whereas the lumbar ES displayed normal activity on both sides of the body. Trunk velocity during both flexion and extension was slower in the patients than in the controls.

Conclusions: Despite the existence of ipsilateral as well as contralateral higher inputs to axial and to a lesser extent also to more lateral trunk muscles, the function of the superficial abdominal muscles and of the LD muscle is adversely affected by a contralateral stroke. Conversely, the lumbar ES, which can be categorized as local trunk extensors, seem to normally fulfill their anti-gravitational task on both sides of the body.