Biomechanics of descending ramps

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This study investigated the biomechanics of human gait while descending ramps. Fifteen young, healthy subjects (20–30 years) walked self-paced down an instrumented ramp while ground reaction forces (GRF) and sagittal plane body movements were recorded. Ramp angles were set at 0, 5, 10, 15, and 20 degrees. Joint angles for the ankle, knee and hip were found to be most affected by ramp angle during the second half of stance. The primary change in kinematics occurred at the knee while lowering the body to the next step down the ramp. Step length and period decreased as ramp angle increased; however, gait speed did not significantly change. Shear GRFs were found to increase with ramp angle. Calculated sagittal plane joint moments at the knee, and to a lesser extent the ankle and hip, were affected by ramp angle. Knee extension moments showed large increases with increased ramp angle. An increasing dorsiflexion moment of the ankle with increasing ramp angle was found during the first 20% of stance phase. These results suggest that young, healthy individuals maintain relatively constant gait kinematics, particularly during the first half of stance phase, while descending ramps. This requires significant increases in the moment at the knee as ramp angle is increased.