ABSTRACT
Chronic ankle instability (CAI) is a common condition in athletes, which can alter the muscular activity of lower limb during jump. The objective of the study was to verify the magnitude of activation, onset timing and order of recruitment of the proximal and local muscles to the ankle of young athletes with CAI during a single leg vertical jump. Thirty-seven athletes were selected and divided into: 1) CAI group and 2) control group. An electromyographic evaluation was performed during the jump on force plate. The muscles evaluated were the proximal muscles - gluteus medius (GMed), rectus femoris (RF) and local ankle muscles - tibialis anterior (TA), peroneus longus (PL) and lateral gastrocnemius (LG). In propulsion, the CAI group showed early activation of all evaluated muscles, when compared to control group (p = 0.05). No diferences were found between groups concerning magnitude of electromyographic signal and order of muscle recruitment. During landing, an increase in magnitude of the electromyographic signal of TA in the CAI group was observed and no diferences were found between groups for onset activation and order of muscle recruitment. The results can be applied to athletes' rehabilitation through specific neuromuscular control exercises, such as reaction time and local and proximal joint stabilization to optimize muscle performance and injury incidence. Therefore, in the single leg vertical jump athletes with CAI presented higher activation of the TA in the landing and an early activation of the GMed, RF, TA, PL and LG in propulsion in relation to control group.