Kinetic Compensations due to Chronic Ankle Instability during Landing and Jumping.

Introduction: Skeletal muscles absorb and transfer kinetic energy during landing and jumping, which are common requirements of various forms of physical activity. Chronic ankle instability (CAI) is associated with impaired neuromuscular control and dynamic stability of the lower extremity. Little is known regarding an intra-limb, lower-extremity joint coordination of kinetics during landing and jumping for CAI patients. We investigated the effect of CAI on lower-extremity joint stiffness, and kinetic and energetic patterns across the ground contact phase of landing and jumping. Methods: 100 CAI patients and 100 matched able-bodied controls performed five trials of a landing and jumping task (a maximal vertical forward jump, landing on a force plate with the test leg only, and immediate lateral jump toward the contralateral side). Functional analyses of variance (FANOVA) and independent t-tests were used to evaluate between-group differences for lower extremity net internal joint moment, power and stiffness throughout the entire ground contact phase of landing and jumping. Results: Relative to the control group, the CAI group revealed (i) reduced plantarflexion and knee extension, and increased hip extension moments, (ii) reduced ankle and knee eccentric and concentric power, and increased hip eccentric and concentric power, and (iii) reduced ankle and knee joint stiffness, and increased hip joint stiffness during the task. Conclusion: CAI patients appeared to use a hip dominant strategy by increasing the hip extension moment, stiffness, and eccentric and concentric power during landing and jumping. This apparent compensation may be due to decreased capabilities to produce sufficient joint moment, stiffness and power at the ankle and knee. These differences might have injury risk and performance implications. (C) 2017 American College of Sports Medicine

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