Reliability of isometric muscle testing of knee flexor and extensor muscles in patients with connective tissue disease

Abstract

This two-part study evaluated the reliability of inexpensive devices for isometric muscle testing on patients. First, the relationship between gauge readings of the devices and known weights was evaluated. Coefficients of determination and regression lines were used to determine the strength and nature of this relationship, which was determined to be linear. Second, intratester reliability for force measurements of isometric knee extension and flexion motions was determined for 30 patients with connective tissue diseases. Right knee extensor and flexor muscle forces were measured during two sessions. The measurements between sessions were compared for degree of agreement using intraclass correlation coefficients. Intraclass correlation coefficients ranged from .90 to .95 for knee flexor force measurements and from .75 to .85 for knee extensor force measurements. Based on the results of this study, this measuring device can be used reliably to measure knee extensor muscle force at 50 degrees and knee flexor muscle force at 30 and 70 degrees.