EFFECT OF PERIPHERIAL AFFERENT ALTERATION OF THE LATERAL ANKLE LIGAMENTS ON MUSCLE ACTIVITY DURING DYNAMIC ACTIVITY

Abstract

Published data suggest that peripheral afferent information arising from capsuloligamentous mechanoreceptors affect muscle stiffness, reflex, and motor control through influence on the gamma motor system. The purpose of this study was to assess the role that peripheral afferent feedback from the lateral ankle ligaments plays in muscle activity during walking and running. Thirteen normal, healthy subjects (7 males, 6 females) attended two testing session, At each testing session, subjects performed treadmill walking (3.2km/hr) and running (7.6km/hr) before and 20 minutes after being bilaterally injected with either a 1.5% lidocaine solution (LS) or a placebo solution (PS) (.9% sodium chloride). With the subject blinded, solutions were injected directly into anterior talofibular or calcaneofibular ligaments (1.5 cc per ligament). The order of injection was counterbalanced between subjects. During the treadmill activities, electromyographical (EMG) activity of the anterior tibialis (AT), peroneus longus (PL), peroneus brevis (PB), and gluteus medium (GM) was collected. EMG signals from 12 cycles were amplitude normalized to the mean ensemble average of the pretest for each respective condition. Cycles were time normalized and further divided into stance and swing phases. The mean amplitude and coefficient of variation for each muscle, phase, and condition were used for data analysis. Separate repeated measures ANOVA models demonstrated decreased mean amplitude of the PL during the swing phase of walking, AT during the swing phase of running, and PL and PB during the stance phase of running between pretest and posttest. No significant differences existed between the LS and PS conditions. No significant interactions were revealed for the coefficient of variation data. While these results fail to demonstrate differences in muscle activity between the LS and PS conditions, the results mimic previously published data at the knee joint. Distension of the ligamentous tissue by the injected solutions may have altered peripheral afferent information, thereby causing an inhibitory response of the dynamic ankle stabilizers. Clinically, these findings suggest that dynamic stability may be compromised following joint injury that is associated with swelling.