11 Preparation time influences ankle joint control during dynamic change of direction movements

Abstract

BackgroundThe influence of preparation time on ankle joint biomechanics during highly dynamic movements is largely unknown. In addition, limited time to prepare dynamic movements may be a factor in the aetiology of ankle joint injuries.ObjectiveTo evaluate the impact of limited preparation time on ankle joint loading during highly dynamic run-and-cut movements.DesignCross-sectional study with repeated measures (3 time conditions).SettingUniversity biomechanics laboratory.ParticipantsThirteen male athletes from a high risk sport for ankle sprains (basketball).InterventionsParticipants performed 45°-sidestep-cutting and 180°-turning manoeuvres on a force plate in reaction to light signals which appeared during the approach run. Both movements had to be executed under three different time conditions: (1) an easy condition, in which the light signal appeared very early, (2) a medium condition and (3) a hard condition in which the participants had very little time to prepare the movements.Main outcome measurementsMaximum ankle inversion angles, moments and velocities during ground contact were evaluated. In addition, EMG signals of three lower extremity muscles were analysed.ResultsIn 180°-turning movements, reduced preparation time led to significantly increased maximum ankle inversion velocities (p = 0.03; η2 = 0.246). In addition, maximum ankle inversion moments increased in the medium condition when compared to the easy condition (p = 0.03). Muscular activation levels did not change. Ankle joint loading was not affected by preparation time in 45°-cutting movements.ConclusionsThe increased inversion velocities and moments, without accompanying changes in muscular activation, are likely to put the ankle joint at a higher injury risk during turning movements. Preparation time should be considered in ankle injury research, ankle stability training programs and in the aetiology of ankle sprains.