The purpose of this study was to examine the effect of chronic ankle instability (CAI) on eccentric peak torque of the ankle musculature. The study included fifty participants divided into two groups; the first group consisted of twenty five subjects suffering from CAI, the second group consisted of twenty five subjects with no prior history of ankle injury as control group. Eccentric peak torque of invertors, evertors, plantar-flexors and dorsiflexors was recorded for each participant at angular velocities 30 and 90o/sec by using (Biodex Medical Systems, Inc, Shirley, NY, USA). Analysis of variance (ANOVA) revealed that there was a significant deficit for eccentric inversion, eversion, and plantar flexion peak torques between CAI group and control group at both angular velocities (p< 0.05). However, no significant difference was identified for eccentric dorsiflexion peak torque at both angular velocities (p> 0.05). There was no significant increase in eccentric torque of invertors, evertors, plantar-flexors and dorsiflexors when the angular velocity increased from 30 to 90°/sec for normal and CAI group (p> 0.05). Eccentric strengthening of invertors, evertors, and plantar-flexors must be considered during rehabilitation of subjects suffering from chronic ankle instability.
Key words: Eccentric contraction, ankle muscles, chronic ankle instability
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