Description and Intrarater Test-Retest Reliability of a Reverse-Action Method to Assess Ankle Evertor Muscle Performance: The I-to-V Test.

Abstract

Purpose: Reverse action (RA) of the ankle evertor muscle is when the proximal attachment moves toward the distal attachment, moving the lower leg in the frontal plane when the foot and ankle are fixed on the ground and inducing ankle eversion. The purpose of this study was to describe an RA method for measuring ankle evertor muscle performance. Method: Eighteen healthy individuals were recruited for this study. To assess the RA of their ankle evertors, the participants sat with their knees together and their feet firmly planted on the floor, then spread their knees as far apart as possible. A tester used a measuring tape to measured the distance (in cm) between the medial tibial tuberosity of the tested side and that of the non-tested side. In the end range position of the RA, ankle evertor electromyographic activity was recorded simultaneously. The intra-class correlation coefficient (ICC) and standard error of measurement (SEM) were calculated to establish the intrarater test-retest reliability. The correlation between each performance value and muscle activity was assessed using a linear correlation model. Results: The proposed method of assessing RA performance was highly reliable (ICC=0.95) and had a low SEM (1.63 cm); in addition, the performance value showed a strong positive correlation with ankle evertor muscle activity (ρ=0.90; 95% CI: 0.79, 0.95; p=0.01). Conclusions: The proposed RA method of assessing the ankle evertor muscles can be used as a simple, reliable, economical performance test. It can also be used as an alternate method of testing the peroneal muscles rather than selectively measuring ankle evertor performance because hip external rotation occurs when performing RA.