Relationship between Muscular Strength and Functional Balance in People Post-Stroke

Abstract

Impaired balance and weak muscle strength are common deficits associated with stroke. These deficits increase the risk of fall among people post-stroke. The relationship between muscular strength and balance was previously reported to be weak. However, the conclusion was made based on clinical balance assessments instead of biomechanical data. Limited research examined the relationship between balance and strength in people post-stroke. PURPOSE: To investigate the relationship between muscular strength and functional balance in people post-stroke. METHODS: A total of 20 people post-stroke completed balance and strength assessments over two separate visits. A computerized dynamic posturography system (NeuroCom International, Clackamas, OR, 2010) was used to perform four balance tests including limits of stability test (LOS), sit to stand test (STS), walk across test (WA), and step up and over test (SUO). In addition, participants completed isometric muscle strength tests of the trunk, hip, knee, and ankle. Peak torque was measured with a computerized dynamometer (Biodex Medical Systems Inc, Shirley, NY, 2012). Pearson’s correlation test was used for statistical analysis. RESULTS: There was a strong correlation between max excursion (LOS test) and muscle strengths of knee flexor/extensor on the affected side (r values ranged between 0.721 and 0.793, p<0.04). A strong correlation was also found between step width (WA test) and muscular strengths of trunk extensor, knee flexor, ankle plantar-flexor, hip flexor and extensor on the unaffected side (r values ranged between 0.797 and 0.902, p<0.01). STS and SUO did not show any significant correlation with muscle strength. CONCLUSIONS: Our findings suggest that strengthening of the knee flexor/extensor may help people post-stroke to shift the weight to maximum range without losing balance. Also, our results indicate that the strength of the core and lower extremities muscles is strongly associated with gait stability.