Muscle activation changes during body weight support treadmill training after focal cortical ischemia: A rat hindlimb model

The study used a focal ischemia rat hindlimb model to investigate muscle activity changes during a 10-day body weight support (BWS) treadmill training program. The changes being studied included fatigue effects, EMG burst duration in the gait cycle, and the symmetry of muscle activation between affected and unaffected sides. Intramuscular EMG of medial gastrocnemius (MG) and tibialis anterior (TA) muscles in male Sprague Dawley rats at affected side (n=10) and unaffected side (n=10) were recorded during the treadmill running before a middle cerebral artery occlusion/reperfusion (MCAo/r) surgery and poststroke recovery stage. Behavioral test score and bodyweight were recorded at a daily basis after stroke. The mean power frequency (MPF) of the EMG, EMG burst duration in the gait cycle, and symmetry index between two sides were used for analysis. The drop rate of MPF of MG at the unaffected side increased (P<0.05) at poststroke day 2 and it generally decreased along the poststroke training days and almost returned to baseline value at poststroke day 6. Symmetry index of MG and TA showed a large imbalance right after stroke and tended to return to normal. Our findings of the MPF drop after stroke might indicate fatigue effects due to the compensation loading share of the ipsilateral side muscle and the increase of the symmetry index reflects abnormal gait pattern after the onset of stroke. The recovery rate after stroke could be investigated with EMG parameters together with the behavioral score, and both were improved during and after the BWS treadmill training.