Figure 2

Perturbation platform used during balance training. Photographs of the training platform, configured for training of: A. stepping reactions, and B. grasping reactions. The surface of the platform is controlled to move 30 cm either forward, backward, left or right by means of pneumatic cylinders; the perturbation magnitude (platform velocity and acceleration) is altered by changing the pressure of the air delivered to the cylinders. A dual-axis accelerometer measures the magnitude and timing of the platform acceleration. During grasping training, handrails (equipped with force-sensing resistors to provide information about the timing of the reactions) are mounted on the platform, on one or both sides of the subject. These handrails are positioned at varying heights (87–101 cm) and distances from the subject (37–42 cm from midline) to simulate variability in handrail placement in daily life. Foam blocks are used to prevent foot movement and promote reliance on grasping reactions. A safety harness is worn at all times during training. (Image used with the consent of the model.)