Reliability of EasyForce Dynamometer for Assessment of Maximal Knee and Hip Strength, and Comparison to Rigid Isometric Dynamometers with External Fixation

This study aimed to assess intra- and inter-visit reliability of a novel EasyForce dynamometer for assessment of maximal strength in knee extension and flexion, and hip abduction and adduction tasks. Young healthy participants (n = 50; 25 males, 25 females; age: 23.4 ± 2.1 years) were measured for maximal joint torque with EasyForce dynamometer and rigid isometric dynamometers with external fixation, in two-sessions (5-10 days apart). The intra-visit reliability was high (ICC) = 0.84-0.95 knee; 0.90-0.94 hip), with absolute reliability sometimes exceeding the acceptable threshold (CV = 6.9-10.6% knee; 7.8-11.8% hip). Inter-visit reliability was excellent for all tasks (ICC = 0.95-0.97 knee; 0.95-0.96 hip). Although the EasyForce values were different compared to rigid dynamometers, the correlations between the devices were high (r = 0.64-0.75 knee; 0.70-0.75 hip). In conclusion, the EasyForce dynamometer provides reliable means of assessing knee (extension and flexion) and hip (abduction and adduction) muscle strength.