Background and Aim: Since utilization of different patterns to perform voluntary movements influence human function, the aim of this study was to compare the selected kinematic parameters of active males in voluntary and involuntary gait initiation.

Materials and Methods: In this quazi-experimental study 13 young male subjects with age (23.3±3.1) years, height (1.75±.13) m, weight (68.9±7) kg and body mass index (22.4±1.8) k/m2, performed initiation of gait in 6 trials included three voluntary and three involuntary. Kinematic parameters measured by motion analysis system. K-S test was used to ensure the normal distribution of data and dependent T- test to compare within group variable at P0.05 level.

Result: The results showed that use of perturbation that leads to the initiation of motion, increased distance (p: 0.00) and velocity (p: 0.00) and reduced the time of gait initiation (p: 0.00), swing time (p: 0.00), stance time (p: 0.00) and double support time (p: 0.00), increased the amount of hip (p: 0.00) and knee flexion (p: 0.00) and decreased the amount of ankle dorsiflexion (p: 0.00). In addition, the displacement of the center of mass in the medio-lateral and vertical directions was decreased (p=0.03) and increased (p=0.01) respectively. Conclusion: The results indicate significant changes in most of the spatio-temporal parameters of gait initiation as a result of using Perturbation that leads to the initiation of motion. The results of this study can be recommended to be used in the field of gait initiation studies as well as in clinical cases to diagnose the normal and abnormality.