Eccentric/concentric ratios at selected velocities for the invertor and evertor muscles of the chronically unstable ankle.

Abstract

The use of muscle balancing by the clinician to determine return to activity or discharge of a patient is not a well understood measure. Because of the lack of information on the poorly understood concept of eccentric/concentric (E/C) ratios at the ankle, the purpose was to determine the E/C ratios for the invertor and evertor muscles at various velocities in healthy and chronically unstable ankles. Ten subjects with healthy ankles and 14 with chronically unstable ankles performed five maximal effort reciprocal eccentric/contraction contractions on an isokinetic dynamometer at four velocities (60, 120, 180, and 240 degrees/s) and for each physiological movement of inversion and eversion. Data were analysed using a two way mixed model analysis of variance with repeated measures, with Tukey's test used for post hoc analysis. Although the chronically unstable ankle was significantly weaker (p < 0.05) eccentrically and concentrically for inversion and eversion, the main effect of the E/C ratios for the ankle was not significant for either joint motion. The main effect of velocity was significant (p < 0.05) for each joint motion, but no significant interaction effects were observed. As velocity increased, the E/C ratio increased, except at 180 and 240 degrees/s for either ankle group. Chronic ankle instability and muscle weakness co-exist. Adequate E/C ratios in the chronically unstable ankle may exist in the absence of normal strength values.