Ramp Angle, Not Plateau Height, Influences Transition Strategies

In a previous study, we found that participants modified how they transitioned onto and off of ramp configurations depending upon the incline. While the transition strategies were originally attributed to ramp angles, it is possible that the plateau influenced the strategies since the final surface height also differed. Ultimately, for the current study, we hypothesized that an individual's transition strategies would have significant main effects for ramp angle, but not plateau height. Twelve healthy, young adults transitioned onto 3 distinct ramp configurations, a 2.4-m ramp angled at 12.5° ending at a plateau height of 53 cm, a 1.2-m ramp angled at 23.5° ending at a plateau height of 53 cm, and a 2.4-m ramp angled at 23.5° ending at a plateau height of 99.5 cm. Kinematics, kinetics, and muscle activity were measured during the stance phase before contacting the ramp. In support of our hypothesis, impact peak, active peak, and all of the muscle activity variables had a significant main effect for ramp angle, with greater vertical force peaks and muscle activity on steeper ramp transitions. These findings support our previous interpretation that individuals use estimations of ramp angle, not plateau height, to determine their transition strategies.