Magnitude and variability of gait characteristics when walking on an irregular surface at different speeds

•Speed influences gait similarly when walking on a regular and irregular surface.•Joint flexion and muscle activity increases with increasing walking speed.•Increasing speed results in a decrease variability of biomechanical parameters.•Irregular walking causes altered gait characteristics compared to regular walking.•The benefits of walking on an irregular surface may be heightened at slower speeds. Different modes of perturbations have been used to understand how individuals negotiate irregular surfaces, with a general notion that increased locomotion variability induces a positive training stimulus. Individuals tend to walk slower when initially exposed to such locomotion tasks, potentially influencing the magnitude and variability of biomechanical parameters. This study investigated theeffects of gait speed on lower extremity biomechanics when walking on an irregular (IS) and regular surface (RS). Twenty physically active males walked on a RS and IS at three different speeds (4 km/h, 5 km/h, 6 km/h). Lower extremity kinematics (300 Hz) and surface electromyography (3000 Hz) were recorded during the first 90 s of gait. Two-factor repeated measures ANOVA was used to determine surface and speed effects (p