The Relationship between Eccentric and Concentric Measures of Ankle Strength and Functional Equinus in Classical Dancers

Abstract

Classically trained dancers possess a supernormal range of motion in ankle plantar flexion with a reciprocally diminished range of motion in ankle dorsiflexion. Restricted joint motion is considered homologous with diminished strength in muscle groups associated with the lost motion and is associated with compensatory hypermobility in neighboring joints. The purpose of this study was to measure clinical and functional ranges of ankle motion and to assess peak torque values for ankle plantar flexion and dorsiflexion collected both eccentrically and concentrically. Twelve professional, classical dancers (6 males, 6 females) were measured goniometrically for ankle range of motion using three different positioning techniques and for isokinetic peak torques of ankle plantar flexion (PF) and dorsiflexion (DF) at two different joint angles and two different speeds. Measured by traditional goniometric techniques, ankle dorsiflexion was limited relative to published norms and significantly lower than measures taken when the dancer assumed a functional testing position. A relationship of moderate strength between dorsiflexion range and peak torque values was obtained, although it did not meet our criterion for significance. No significant differences were seen in either gender between concentric and eccentric measures of ankle strength for any of the testing conditions. The equality of concentric and eccentric measures may reflect a training effect resulting from regularly practiced concentric relevé activities or may be a result of limitations in the laboratory setting.