Effect Of Load On Biomechanical Characteristics During Step-down Activity

PURPOSE:The step-down activity is an important daily function, and varying weight loads can alter the gait characteristics of the human body. However, the impact of different loads on human gait during the step-down activity remains unclear. This study examines the effects of various loads on human gait during step-down activity from a biomechanical perspective. METHODS:Ten male subjects participated in the study (age range: 23-26 years; height: 176.6 ± 5.0 cm; weight: 71 ± 8.3 kg). Each subject was tested under three loading conditions: no load, 15 kg load, and 30 kg load, with weights applied via weight-bearing vests evenly distributed across the body. The test was conducted on a 30 cm high step, with participants walking continuously for 15 steps at a frequency of 90 steps/min. Gait indices were collected using the Pedar-X plantar pressure test system. Data analysis was performed using R 4.3.2, and one-way ANOVA was used to compare the effects of different loads on each gait index. RESULTS:During step-down activity, an increase in load corresponded to significant increases in peak foot force and impulse (peak force: no load = 846.2 ± 200.1 N, 15 kg = 928.4 ± 169.0 N, 30 kg = 1102.6 ± 249.3 N, P = 0.032; peak impulse: no load = 250.3 ± 66.3 Ns, 15 kg = 270.2 ± 66.8 Ns, 30 kg = 386.8 ± 92.2 Ns, P < 0.01). Although plantar pressure increased with load, this increase was not statistically significant (peak pressure: no load = 172.2 ± 32.1 kPa, 15 kg = 197.7 ± 45.9 kPa, 30 kg = 224.6 ± 65.5 kPa, P = 0.080). No significant difference was observed in the maximum contact area between the foot and the ground (no load = 134.7 ± 17.3 cm2, 15 kg = 137.1 ± 12.7 cm2, 30 kg = 142.2 ± 15.4 cm2, P = 0.543). There was a significant increase in support phase time with increased load (no load = 0.567 ± 0.081 s, 15 kg = 0.569 ± 0.062 s, 30 kg = 0.642 ± 0.066 s, P = 0.037), though no significant difference was found in the single-step gait cycle time (no load = 0.977 ± 0.039 s, 15 kg = 0.979 ± 0.047 s, 30 kg = 1.028 ± 0.089 s, P = 0.137). CONCLUSIONS:(1)During step-down activity, increasing load significantly elevates foot peak force and impulse.(2)Increased load extends the support phase time but does not affect the overall gait cycle time.