Objectives: To study electromyographic characteristics of anticipatory postural adjustment in axial and lateral, posterior and anterior trunk muscles during the performance of upper-and lower-limb flexion tasks, in subjects with hemiparesis after stroke and to determine the relationship between anticipatory activity and subjects' motor and functional status.
Design: A nonrandomized control study.
Setting: Geriatric rehabilitation center in Israel.
Participants: Fifty poststroke hemiparetic patients and 30 healthy control subjects.
Intervention: Electromyographic activity of the lumbar erector spinae and of the latissimus dorsi muscles was recorded bilaterally during flexion of either arm and from the 2 rectus abdominis and obliquus externus muscles during flexion of either hip.
Main outcome measures: Muscles' onset latency, cross-correlation values between the temporal activation profile of corresponding pairs and between ipsilateral muscular pairs, symmetry in activation magnitude of corresponding muscles, and relation between electromyographic activity and motor and functional performance
Results: Onset latencies of trunk muscles were partially delayed in the patients with longest hindrance displayed by the erector spinae ipsilateral to the flexing arm (P<.04). Temporal synchronization between pertinent muscular pairs was lower in the patients than in the healthy subjects, with significant group differences (P<.05 or lower) in the correlations between ipsilateral pairs of trunk muscles. Activation of the corresponding lateral trunk muscles in the patients was significantly less symmetrical than in the controls (P<.03 or lower) because of reduced activity on the paretic body side, especially on flexing of the paretic limbs. Conversely, in the controls as well as on the nonparetic side of the patients, limb flexion was associated with increased activity in the ipsilateral lateral trunk muscle. The erector spinae muscle in both groups and on both sides was more active on the contralateral side than on the ipsilateral side to the flexing arm. The reduced activity level in trunk muscles on the paretic body side was associated with deficiencies in motor and functional abilities.
Conclusions: Major impairments in the activity of trunk muscles in hemiparetic subjects were manifested in the reduced activity level of the lateral trunk muscles, in delayed onset, and in reduced synchronization between activation of pertinent muscular pairs. These problems were associated with motor and functional deficits and warrant specific consideration during physical rehabilitation of post stroke hemiparetic patients.