Reliability of ankle dorsiflexor muscle strength, rate of force development, and tibialis anterior electromyography after stroke

Abstract

Background: Measures of hemiparetic ankle dorsiflexor muscle strength and rate of force development (RFD) are often used to determine the efficacy of rehabilitation interventions after stroke. However, evidence supporting the reliability of these measures is limited. This brief report provides a secondary analysis investigating the between-session reliability of isometric ankle dorsiflexor muscle strength, rate of force development (RFD), and tibialis anterior electromyography (TA EMG), in people with chronic stroke. Method: Participants (n=15) completed three maximal isometric contractions of the ankle dorsiflexor muscles as fast as possible using a rigid dynamometer. Tests were repeated seven days later. Outcomes included ankle dorsiflexor isometric maximal voluntary contraction (MVC), RFD in the first 200ms (RFD200ms), time to reach 90% MVC, and peak TA EMG. Data were analysed for 13 participants using intra-class correlation coefficients (ICC) and standard error of the measure (SEM). Results: When the mean of three trials was analysed, there was excellent reliability for isometric dorsiflexor MVC (ICC 0.97 [95% CI 0.92-0.99]), moderate reliability for TA EMG (ICC 0.86 [0.60-0.96]) and time to reach 90% MVC (ICC 0.8 [0.53-0.93]) and poor reliability for dorsiflexor RFD200ms (ICC 0.79 [0.48-0.92]). Conclusion: Given the functional significance of the ankle dorsiflexors, future research should investigate more reliable methods for measuring rapid force production in the dorsiflexor muscles after stroke.