Patients with Parkinson's disease (PD) have difficulties in performing complex bimanual movements. Here we have examined acquisition and performance of a bilateral obstacle stepping task to see whether these difficulties are also present during bipedal movements. Subjects had to minimize foot clearance when repeatedly stepping on a treadmill over randomly approaching obstacles on either side. The subjects had full vision and received acoustic feedback information about task performance. Foot clearance improved in healthy and PD subjects during the acquisition of the task. However, PD subjects showed a slower improvement and achieved a poorer performance level. Thus, in contrast to unilateral obstacle stepping, where no deficits in performance after task repetition were found in PD subjects, bilateral obstacle stepping was poorer in these subjects compared to healthy subjects. The present results extend findings from upper to lower limb movements, namely that PD subjects have difficulties in the performance of bilateral motor task
