People with chronic ankle instability benefit from brace application in highly dynamic change of direction movements.

BACKGROUND: The application of ankle braces is an effective method for the prevention of recurrent ankle sprains. It has been proposed that the reduction of injury rates is based on the mechanical stiffness of the brace and on beneficial effects on proprioception and neuromuscular activation. Yet, how the neuromuscular system responds to the application of various types of ankle braces during highly dynamic injury-relevant movements is not well understood. Enhanced stability of the ankle joint seems especially important for people with chronic ankle instability. We therefore aimed to analyse the effects of a soft and a semi-rigid ankle brace on the execution of highly dynamic 180° turning movements in participants with and without chronic ankle instability. METHODS: Fifteen participants with functional ankle instability, 15 participants with functional and mechanical ankle instability and 15 healthy controls performed 180° turning movements in reaction to light signals in a cross-sectional descriptive laboratory study. Ankle joint kinematics and kinetics as well as neuromuscular activation of muscles surrounding the ankle joint were determined. Two-way repeated measures analyses of variance and post-hoc t-tests were calculated. RESULTS: Maximum ankle inversion angles and velocities were significantly reduced with the semi-rigid brace in comparison to the conditions without a brace and with the soft brace (p ≤ 0.006, d ≥ 0.303). Effect sizes of these reductions were larger in participants with chronic ankle instability than in healthy controls. Furthermore, peroneal activation levels decreased significantly with the semi-rigid brace in the 100 ms before and after ground contact. No statistically significant brace by group effects were found. CONCLUSIONS: Based on these findings, we argue that people with ankle instability in particular seem to benefit from a semi-rigid ankle brace, which allows them to keep ankle inversion angles in a range that is comparable to values of healthy people. Lower ankle inversion angles and velocities with a semi-rigid brace may explain reduced injury incidences with brace application. The lack of effect of the soft brace indicates that the primary mechanism behind the reduction of inversion angles and velocities is the mechanical resistance of the brace in the frontal plane.

Ankle Joint Control in People with Chronic Ankle Instability During Run-and-cut Movements.

Despite a considerable amount of research, the deficits causing recurrent sprains in people with chronic ankle instability are still unclear. Changes in frontal plane kinematics and decreased peroneal activation have been proposed as potential underlying mechanisms, but whether people with ankle instability show deficits in control of injury-relevant movements is not well understood. Therefore, the purpose of the present study was to analyse ankle joint kinematics and kinetics as well as neuromuscular activation during dynamic change-of-direction movements. Eighteen participants with functional instability, 18 participants with functional and mechanical instability and 18 healthy controls performed 45° sidestep-cutting and 180° turning movements in reaction to light signals. During sidestep-cutting both instability groups displayed significantly lower inversion angles than controls when the trials with the highest maximum inversion angle of each participant were compared. In turning movements, participants with functional instability presented significantly lower average maximum inversion angles than controls as well as higher peroneal activation before foot strike than participants with both functional and mechanical instability. We theorize that the observed changes in movement kinematics of participants with chronic ankle instability are the result of a protective strategy to limit frontal plane ankle joint loading in potentially harmful situations.

Preparation time influences ankle and knee joint control during dynamic change of direction movements.

The influence of preparation time on ankle joint biomechanics during highly dynamic movements is largely unknown. The aim of this study was to evaluate the impact of limited preparation time on ankle joint loading during highly dynamic run-and-cut movements. Thirteen male basketball players performed 45°-sidestep-cutting and 180°-turning manoeuvres in reaction to light signals which appeared during the approach run. Both movements were executed under (1) an easy condition, in which the light signal appeared very early, (2) a medium condition and (3) a hard condition with very little time to prepare the movements. Maximum ankle inversion angles, moments and velocities during ground contact, as well as EMG signals of three lower extremity muscles, were analysed. In 180°-turning movements, reduced preparation time led to significantly increased maximum ankle inversion velocities. Muscular activation levels, however, did not change. Increased inversion velocities, without accompanying changes in muscular activation, may have the potential to destabilise the ankle joint when less preparation time is available. This may result in a higher injury risk during turning movements and should therefore be considered in ankle injury research and the aetiology of ankle sprains.