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Context:Rehabilitation programs for patients with chronic ankle instability (CAI) generally involve balance-perturbation training (BPT). Anticipatory postural adjustments (APAs) and compensatory postural adjustments (CPAs) are the primary strategies used to maintain equilibrium during body perturbations. Little is known, however, about how APAs and CPAs are modified to promote better postural control for individuals with CAI after BPT.Objective: To investigate the effect of BPT that involves kicking a ball on postural-control strategies in individuals with CAI.Design: Randomized controlled clinical trial. Setting: Laboratory. Patients or Other Participants: We randomly assigned 44 volunteers with CAI to either a training group (TG; 11 women, 11 men; age ¼ 24 6 4 years, height ¼ 173.0 6 9.8 cm, mass ¼ 72.64 6 11.98 kg) or control group (CG; 11 women, 11 men; age ¼ 22 6 3 years, height ¼ 171.0 6 9.7 cm, mass ¼ 70.00 6 11.03 kg).Intervention(s): The TG performed a single 30-minute training session that involved kicking a ball while standing on 1 foot. The CG received no intervention.Main Outcome Measure(s): The primary outcome was the sum of the integrated electromyographic activity ( PR EMG) of the lower extremity muscles in the supporting limb that were calculated during typical intervals for APAs and CPAs. A secondary outcome was center-of-pressure displacement during similar intervals.Results: In the TG after training, the PR EMG decreased in both dorsal and ventral muscles during compensatory adjustment (ie, the time interval that followed lower limb movement). During this interval, muscle activity ( PR EMG) was less in the TG than in the CG. Consequently, center-of-pressure displacement increased during the task after training.Conclusions: A single session of ball-kicking BPT promoted changes in postural-control strategies in individuals with CAI. These results should stimulate new and more comprehensive studies to investigate the effect of this and other BPT techniques on postural control in patients with CAI.Key Words: recurrent sprains, reactive responses, balance training Key PointsAfter balance-perturbation training, postural sway increased during the ball-kicking activity and decreased during a static task in individuals with chronic ankle instability. Ventral and dorsal muscle activity decreased just before kicking the ball, and tibialis anterior and peroneus longus activity increased after the kick in the balance-perturbation-training group. Researchers should conduct more comprehensive studies to determine if balance-perturbation training improves postural control and simultaneously augments ankle stability in individuals with chronic ankle instability.

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The purpose of this study was to investigate the anticipatory (APA) and compensatory (CPA) postural adjustments in individuals with Parkinson’s disease (PD) during lateral instability of posture. Twenty-six subjects (13 individuals with PD and 13 healthy matched controls) were exposed to predictable lateral postural perturbations. The electromyographic (EMG) activity of the lateral muscles and the displacement of the center of pressure (COP) were recorded during four time intervals that are typical for postural adjustments, i.e., immediately before (APA1, APA2) and after (CPA1 and CPA2) the postural disturbances. The magnitude of the activity of the lateral muscles in the group with PD was lower only during the CPA time intervals and not during the anticipatory adjustments (APAs). Despite this finding, subjects with PD exhibit smaller COP excursions before and after the disturbance, probably due to lack of flexibility and proprioceptive impairments. The results of this study suggest that postural instability in subjects with PD can be partially explained by decreased postural sway, before and after perturbations, and reduced muscular activity after body disturbances. Our findings can motivate new studies to investigate therapeutic interventions that optimize the use of postural adjustment strategies in subjects with PD.