<qa>  What is the task of the subject standing on a platform?- Movement task: The subject stands on a platform with markers placed at different parts of the body to record body movements. A cap with electrodes metal disks is placed on the head for electrocardiographic EEG recording of the electrical activity of the brain brain waves during the experiment. The positions of the feet on the platform are measured. While standing on the platform, the subject leans forward and backward as far as possible without losing balance. Subjects are secured in a safety harness to prevent actual falls. The task is repeated 5 times. The experiment lasts up to 2 hours. 