Isokinetic muscle testing for weak patients suffering from neuromuscular disorders: A reliability study

Precise, sensitive muscle strength testing methods are needed to investigate muscle function in patients with neuromuscular disorders (NMD). Here, we describe an isokinetic knee flexor and extensor testing procedure using the Biodex 3®’s continuous passive motion (CPM) mode. The torque values recorded during passive isokinetic motion were subtracted from the torque values obtained for the same movement with maximal, concentric effort. The aims of the present study were to (i) evaluate the method’s reliability in NMD patients presenting mild to severe muscle weakness and (ii) study the relationship between manual muscle testing (MMT) and isokinetic dynamometry. The fifteen participating patients were tested twice; the respective intraclass correlation coefficients (ICCs) for the two sessions ranged from 0.91 to 0.99 for the peak torque, work and power and from 0.50 to 0.90 for the angle at peak torque. The Spearman rho correlation coefficients comparing isokinetic values and MMT values ranged from 0.67 to 0.74 (p < 0.01). This reliable, dynamic method appears to be of great value in NMD evaluation when sensitive strength measurement at the knee is required.