Characteristics associated with improved knee extension after strength training for individuals with cerebral palsy and crouch gait

Abstract

Muscle weakness may contribute to crouch gait in individuals with cerebral palsy, and some individuals participate in strength training programs to improve crouch gait. Unfortunately, improvements in muscle strength and gait are inconsistent after completing strength training programs. The purpose of this study was to examine changes in knee extensor strength and knee extension angle during walking after strength training in individuals with cerebral palsy who walk in crouch gait and to determine subject characteristics associated with these changes. A literature review was performed of studies published since January 2000 that included strength training, three-dimensional motion analysis, and knee extensor strength measurements for individuals with cerebral palsy. Three studies met these criteria and individual subject data was obtained from the authors for thirty crouch gait subjects. Univariate regression analyses were performed to determine which of ten physical examination and motor performance variables were associated with changes in strength and knee extension during gait. Change in knee extensor strength ranged from a 25% decrease to a 215% increase, and change in minimum knee flexion angle during gait ranged from an improvement of 9° more knee extension to 15° more knee flexion. Individuals without hamstring spasticity had greater improvement in knee extension after strength training. Hamstring spasticity was associated with an undesired increase in knee flexion during walking. Subject-specific factors such as hamstring spasticity may be useful for predicting which subjects will benefit from strength training to improve crouch gait.

Figure 1

Histograms of (A) percent change in knee extensor strength and (B) change in minimum knee flexion angle during gait after completing a strength training program. Subjects from each of the three studies are shown separately – Damiano (white), Eek (gray), and Unger (black). A negative change in minimum knee flexion angle indicates a more upright posture, or a positive outcome, after strength training. Note that in all three studies the outcomes were variable between subjects.

Figure 2

Average hip, knee, and ankle flexion angles for (A) all subjects, (B) the three subjects with the largest increase in knee extension (best outcomes), and (C) the three subjects with the largest increase in knee flexion (worst outcomes) before and after completing strength training program. Note that although there was no significant change in knee flexion for the group as a whole, there were subsets of subjects with significant positive and negative changes.

Figure 3

Hamstring spasticity (A) and walking speed (B) were associated with change in minimum knee flexion angle (KFA) during stance with a p-value < 0.05.