Assessment of gait stability and preferred walking speed in virtual reality

Purpose Analysis of human gait as well as diagnosis of human locomotion organ should always be conducted with velocity of gait equal to Preferred Walking Speed (PWS). The literature review shows that the PWS value is not the same in real and virtual environment. The aim of this study was to determine PWS values in both environments and to specify values of parameters used in equations enabling PWS calculations on the basis of lower limb length. Methods Research-related tests involved 40 subjects walking on the treadmill and wearing HMD goggles. The spatial scenery made participants feel like during a walk in the park. The tests included measurements of displacements of the COP, allowing for the calculation of the Lyapunov exponent and Floquet Multiplier. Both coefficients were used to identify stability at various gait velocities. Results The analysis revealed that the PWS in relation to gait on the treadmill with VR was lower than the PWS without VR. The final stage of research involved the determination of new values of coefficients of the formula enabling the identification of the velocity of comfort of gait in VR. Conclusions Obtained results proved that PWS in real and virtual environment are different. The lower values were obtained for measurements in VR. On the basis of these results, value of the "a" coefficient, used in PWS calculations on the basis of lower limb length, was re-determined. The new value makes it possible to assess PWS for gait conducted on treadmill in virtual environment, what can be very important in gait evaluation.