Characteristics of walking pattern in subjects with incomplete spinal cord injury and their adaptations to changes in walking speed

Among spinal-cord-injured (SCI) subjects with an incomplete motor function loss that are able to walk, most have an altered walking pattern and a reduced walking speed. This doctoral project had two main objectives. One was to characterize the gait pattern of SCI subjects and compare it to that of normal subjects walking at the same speed. The other objective was to measure the adaptability of their walking pattern to changes in speed, and to find the factors that are limiting their maximal walking speed. The main gait characteristics in SCI subjects found in the first study were: a longer cycle duration, a greater hip excursion, a flexed knee at foot contact and during stance, and changes in the timing and the amplitude of muscle activity. It was showed that SCI subjects could adapt to different speeds, but that their range of speeds is limited. The hip-knee angle cyclographs showed that SCI subjects' intralimb coordination patterns were altered. In normal subjects, even at low speed, the soleus muscle showed a peak of electromyographic (EMG) activity synchronized with push-off, and this peak of activity increased with speed. SCI subjects showed a lower and a flatter profile than that of normal subjects and a diminution of a peak of activity in the soleus muscles at push-off. Increases in treadmill speed in SCI subjects resulted only in a small increase in the amplitude of soleus EMG activity. This increase was not specific to push-off, but rather spread over most of stance duration. The second article showed that maximal stride frequency was the predominant limiting factor of the maximal treadmill-walking speed in SCI subjects. At all speeds, SCI subjects spent longer time in stance, swing and double support phases. The relative time spent in single support is greater at higher walking speed and the difficulty to reduce double support time is a limiting factor. It was concluded that a better understanding of the factors limiting the maximal speed in SCI subjec