Different types of disturbed motor control in gait of hemiparetic patients

The pattern of muscle activation in walking was studied in a group of 26 hemiparetic patients. Electromyograms were taken with surface electrodes from 6 muscle groups of the paretic leg and analysed after rectification and time averaging. The sagittal rotations in hip, knee and ankle joint were determined with intermittent light photography. The muscle activation pattern of each patient was compared to that in healthy subjects as well as to the movements performed by the patient and to the normal movement pattern. The normal patterns of movement and muscle activation were assessed from compiled data from 10 healthy female volunteers and average values of angular displacements and amplitude of intergrated EMG were determined at each 5 per cent of the gait cycle. Change of muscle length was determined with a length recording transducer. Gait capacity varied highly in the group of patients studied and the movement pattern also varied markedly. Three types of abnormal muscle activation pattern were disclosed in the patients. In 9 patients, the calf muscles were prematurely activated in the stance phase, probably due to enhanced stretch reflexes (Type I). In another 9 patients, EMG activity was abolished or extremely low in 2 or more of the muscles examined (Type II). In 4 patients, there was a pathological coactivation of several or all of the muscles during part of the gait-cycle, thus disrupting the normal sequential shift of activity in antagonistic muscles (Type III). In the remaining 4 patients, the muscle activation pattern was more complex and no common pattern was discerned.