Interrater and Intrarater Reliability of the EasyForce Dynamometer for Assessment of Maximal Shoulder, Knee and Hip Strength

Abstract

This study aimed to determine the interrater and intrarater reliability of EasyForce dynamometer for assessing shoulder, knee, and hip muscle strength in healthy young adults. Shoulder, knee, and hip maximal isometric strength were measured using the EasyForce in healthy adults (11 women and 12 men). Three repetitions of shoulder internal rotation, abduction, knee flexion, extension, and hip abduction and adduction were performed. The tests were performed by three raters on the same day. The results showed good to high inter- and intrarater reliability (intraclass correlation coefficient range: 0.63–0.91). Moreover, the absolute reliability of the EasyForce was slightly higher than acceptable for all tests (CV > 10%) except for hip abduction on the right leg (CV = 7.2%). The EasyForce dynamometer can be considered a reliable tool for assessing shoulder internal rotation and abduction, knee extension and flexion, as well as hip abduction and adduction strength. The EasyForce dynamometer showed no differences between the raters’ measurements, which could be of great importance for professionals who want to perform the tests regardless of their strength on the values.