Assessing rate of torque development using hand-held dynamometry after stroke: relationship with gait velocity.

Abstract

INTRODUCTION/BACKGROUND: Rate of torque development has shown promise to provide a stronger link with physical function compared to strength in a range of clinical populations. Current methods of assessment involve cumbersome and expensive equipment. The aim of this study was to examine the test-retest reliability of hand-held dynamometry for assessment of rate of torque development following stroke and compare the contribution of strength and rate of torque development to gait velocity. METHOD: Sixty-three adults following stroke (age: 60 years, 34 male) were recruited in this multi-site, multi-national study. Gait velocity was assessed with the fast paced 10m walk test. Assessment of strength and rate of torque development was performed for seven lower limb muscle groups of both limbs with hand-held dynamometry. Intraclass correlation coefficients were calculated for reliability, Spearman's correlations were used to examine associations and a partial F-test was used to compare strength and rate of torque development in the relationship with gait velocity. RESULTS: Good to excellent test-retest reliability was shown for the assessment of strength and rate of torque development across both lower limbs (ICCs - 0.28-0.97). Strong associations were found between strength and rate of torque development measures indicating potential redundancy (rho = 0.71-0.94). Despite the strong correlations between measures, rate of torque development failed to provide significant value over muscle strength, whereas, isometric strength of all muscle groups (except one muscle group) demonstrated stronger relationships with gait velocity compared to rate of torque development. CONCLUSION: Hand-held dynamometry is reliable for assessment of isometric strength and rate of torque development. The results suggest that muscle strength explains significantly higher amounts of variance in gait velocity following stroke compared with rate of torque development. Further research is needed to examine relationships between dynamic measures of muscle power and gait function.