Effects of semi-immersive virtual reality and manipulation of optic flow speed on gait biomechanics in people post-stroke

Objectives: To investigate how people post-stroke and healthy people experience the addition of semiimmersive virtual reality (VR) and optic flow speed manipulation while walking on a treadmill, and if optic flow speed manipulation could be used in rehabilitation to elicit changes in post-stroke gait biomechanics.Methods: Sixteen people post-stroke and 16 healthy controls walked on a self-paced treadmill. After 2 habituation trials (without and with VR), participants walked 3 more trials under the following conditions of optic flow: matched, slow, and fast. Primary outcome measures were spatiotemporal gait parameters and lower limb kinematics. Secondary outcomes (simulator sickness and enjoyment) were assessed with the Simulator Sickness Questionnaire (SSQ) and visual analogue scales (VAS).Results: VR did not influence the gait biomechanics, and optic flow manipulation had a limited effect. Both groups significantly increased their walking speed with the slow optic flow and decreased their speed with the fast optic flow. For the other gait parameters, only small changes were found. Only people post-stroke had a significant increase on the SSQ and the enjoyment-VAS.Conclusion: Adding semi-immersive VR did not influence the gait pattern, was well tolerated, and enjoyable. Both groups altered their gait parameters when the optic flow speed was adjusted during the protocol. Incorporating such manipulations into treadmill training is feasible, but further research about the type of manipulation and level of immersion is needed.