Affiliations: Department of Medical and Social Care Education, Maurice Shock Medical Sciences Building, University of Leicester, University Road, Leicester, UK
Corresponding author: Seth O’Neill, Physiotherapy Lecturer, Department of Medical and Social Care Education, University of Leicester, Maurice Shock Medical Sciences Building, University Road, Leicester, LE1 9HN, UK. Tel.: +44 0116 2523305; E-mail: firstname.lastname@example.org.
Abstract: STUDY DESIGN: Longitudinal test re-test. OBJECTIVES: To investigate the reliability of isokinetic dynamometry at measuring concentric and eccentric plantarflexion torque in knee flexion and extension. BACKGROUND: Plantarflexor muscle deficits are associated with Achilles tendon disorders. Isokinetic testing is often completed in knee extension to assess force production from both Gastrocnemius and Soleus but testing can also be completed in higher degrees of knee flexion to inhibit Gastrocnemius biasing testing to Soleus in relative isolation. The reliability of these methods of testing has not been robustly determined. METHODS: Thirty-seven physically active healthy volunteers underwent bilateral testing using concentric speeds of 90°/s and 225°/s, and an eccentric speed of 90°/s, in knee extension and 80° knee flexion. A test re-test methodology was employed. Peak Torque, Work and Average Power were assessed using best repetition data. Intra-class correlation coefficients (ICC), absolute standard error of measurements (SEM) and minimal detectable change (MDC) where calculated for all variables. RESULTS: ICC data for peak torque values were 0.73–0.87, work per repetition values 0.73–0.86 and average power per rep values of 0.72–0.85, whilst ICC values for peak torque data represented as a percentage of body weight (% BW) were 0.61–0.83, 0.62–0.84 and 0.59–0.82 respectively. MDC ranged from 2.1–35.9. These results suggest a relatively low to moderate change is required to be confident of an actual change in force output. Five parameters fell below 0.7 ICC threshold, all were measures of the left leg in a flexed knee position. CONCLUSION: Isokinetic dynamometry was reliable for testing plantarflexor torque in knee extension and flexion. Expressing data as a % BW is slightly less reliable when testing the non-dominant leg. The reported MDC is around the observed change reported in intervention studies.