Test-retest Reliability of the Onset of Lower Limb Muscles’ Preactivation During Landing from A Jump in Volleyball Players With Functional Ankle Instability

The Abnormal timing of muscle preactivation during landing from a jump may be one of the main mechanisms of ankle instability in volleyball players. Thus, the purpose of this study was to investigate the test-retest reliability of the onset timing of lower limb muscles’ preactivation during landing in volleyball players with functional ankle instability (FAI).Eighteen professional volleyball players with unilateral FAI participated in this study. They performed four jump-landing trials in forward direction and the reliability of the onset time of five lower limb muscles’ preactivation including gluteus maximus(G.max), gluteus medius(G.med),vastus medialis(VM), peroneus longus(PL) and medial gastrocnemius (MG) was assessed using Intraclass correlation coefficients (ICC), standard errors of measurement (SEM) and co-efficient of variation (CV) after one week interval. During the jump-landing task, high and very high reliability was found for G.max, G.med, VM, PL, MG onset times of preactivation with ICC level of .80, .72, .92, .91 and .80 respectively. The CVs of all onset times of muscle preactivation were less than 10% except for G.med and MG (14.72% and 11.50% respectively).The EMG onsets during landing had high to very high reliability and these parameters were found to be useful in the assessment of timing patterns in subjects with FAI.