Effects of interventions on normalizing step width, during self-paced dual-belt treadmill walking with virtual reality, a randomised controlled trial.

Background: Step width increases during dual-belt treadmill walking, in self-paced mode with virtual reality. Generally a familiarization period is thought to be necessary to normalize step width.

Aim: The aim of this randomised study was to analyze the effects of two interventions on step width, to reduce the familiarization period.

Methods: We used the GRAIL (Gait Real-time Analysis Interactive Lab), a dual-belt treadmill with virtual reality in the self-paced mode. Thirty healthy young adults were randomly allocated to three groups and asked to walk at their preferred speed for 5 minutes. In the first session, the control-group received no intervention, the ‘walk-on-the-line’-group was instructed to walk on a line, projected on the between-belt gap of the treadmill and the feedback-group received feedback about their current step width and were asked to reduce it. Interventions started after 1 minute and lasted 1 minute. During the second session, 7-10 days later, no interventions were given.

The aim of this randomised study was to analyze the effects of two interventions on step width, to reduce the familiarization period.

Retention test after 7-10 days.

• Control-group: no extra instruction.

• ‘Walk on the line’-group: subjects are instructed to walk on a straight line, which was projected on the middle of the between-belt gap of the treadmill. The width of the projected line was 8 cm.

• Feedback-group: in the first minute, before intervention, step width was measured. During the intervention period a number was shown on a screen in front of the subject, indicating the step width in meters. During the intervention period a decreasing percentage of initial, individual, step width resulted in positive feedback (90% during the first 15 sec; 70% during 15-30 sec; 60% during 30-45 sec; 40% during 45-60 sec). A green number indicated a step width smaller than the corresponding percentage (positive feedback), a red number indicated a step width larger than the corresponding percentage (negative feedback). Subjects were instructed ‘to keep, the number shown on the screen, green instead of red, by narrowing their step width’.