Muscular utilization of the plantarflexors, hip flexors and extensors in persons with hemiparesis walking at self-selected and maximal speeds

Gait performance secondary to a stroke is partially dependent on residual muscle strength. However, to pinpoint more precisely the mechanism of this relationship, biomechanical models, such as the muscular utilization ratio (MUR) that integrates both muscle strength and gait parameters into the concept of level of effort, are warranted. The aim of the present study was to evaluate the MUR of plantarflexors, hip flexors and extensor muscles during their concentric action in 17 chronic hemiparetic participants walking at self-selected and maximal speeds. Results revealed that peak MUR increased with gait speed. At self-selected speed (0.73 +/- 0.27 m/s), peak MUR values on the paretic side were 64% (+/- 18.7), 46% (+/- 27.6) and 33% (+/- 25.6) for the plantarflexors, hip flexors and extensor muscles, respectively. At maximal speed (1.26 +/- 0.39 m/s), corresponding values were 77% (+/- 23.6), 72% (+/- 33.0) and 58% (+/- 32.1). Peak MUR showed negative associations (-0.33 < r > -0.68), although not all significant, with voluntary muscle strength. The results of this study indicated that the peak MUR increased with gait speed. The plantarflexors were the most used muscle group at self-selected speed, whereas at maximal speed the three muscle groups showed similar peak MUR values. This last finding suggested an important role of the hip muscles in reaching a faster speed. Lastly, because moderate associations were found between peak MUR values and the voluntary muscle strength of hip flexors and extensors, it can be concluded that the weakest paretic muscle groups show, in general, the highest level of effort during gait. (c) 2006 Elsevier Ltd. All rights reserved.