Study Design. The study was composed of an assessment (1), an easy (2), balanced (3) and hard (4) condition. In the easy condition, the patient had twice the amount of the estimated time for the movement. In the balanced condition the available time for the movement was equal to the estimated time and in the hard condition the patient had half the estimated time for the movement. Each condition was followed by a rest period (RP) during which the NASA-TLX questionnaire was deployed to measure subjective feeling of condition difficulty. While the assessment condition was always presented at the beginning of the experiment and comprised 50 trials, conditions 2-4 were randomly presented for 2 min each.