Control of fast squatting movements after stroke

ObjectiveLittle is known about how residual motor impairments after stroke affect the motor control of fast movements, particularly those that combine postural control and limb movement. The purpose of this study was to examine the influence of stroke on the motor control of fast squatting movements.MethodsSeventeen individuals with hemiparesis and seventeen age- and sex-matched controls performed fast squatting movements. Force platform data, knee acceleration, and electromyographic activity from rectus femoris, biceps femoris, tibialis anterior, soleus, were collected.ResultsSubjects after stroke performed the squats asymmetrically, with reduced velocity and acceleration compared to controls. Subjects with low motor recovery depended on the non-paretic leg to compensate for poor paretic muscle activation whereas subjects with high motor recovery activated muscles in the paretic leg in an adaptive manner, making the movement more symmetrical. Difficulty with postural control was evident by reduced coupling of the timing of the knee movement with the center of pressure excursion.ConclusionsSlow performance of squatting movements was accompanied by altered muscle activation, coupled with impaired postural control.SignificanceFast squatting movements in standing require appropriate muscle activation and postural control, the latter of which can be measured easily with force platform and accelerometer data.

► Motor control of fast squatting movements after stroke is influenced by poor timing of muscle activity, reduced muscle activity and excessive cocontraction.
► The postural adjustments are disrupted after stroke, with the timing of peak COP displacements occurring after the timing of the peak acceleration and deceleration of the knee, compared with the tighter coupling in timing in healthy controls.
► Subjects with higher motor recovery after stroke demonstrated an adaptive strategy with an earlier initiation of the paretic leg in fast squatting movements whereas the low motor recovery group depended on the non paretic leg to compensate for the delayed onset of muscle activity.