As the number of aged and female users increase, vehicle ingress/egress ease is becoming important. Our survey revealed that the muscular load has a significant effect on users' subjective evaluation of ingress/egress ease. In this study, we used EMG (electromyogram) technique to quantitatively analyze the muscular load. First, EMG data were collected at 8 muscle points to analyze muscular activity during ingress/egress motion. Then, the maximum-voluntary-contraction (%MVC) for each muscle was calculated by dividing the measured EMG by the maximum EMG the subject can exert and used as the indicator of the muscular load. The results show that peak overall muscular loads were observed during sitting and standing up motions. Individual muscular loads are maximized in the calf during standing motion and in the thighs during knee-stretching motion. Next, using a reconfigurable mock-up cabin, the relationship between the structural parameters: hip-point-height, seat-depth, and side-support-gap, and the muscular loads on the calf and thighs were analyzed. It is shown that from these experimental data, structural parameters can be chosen to obtain a minimum muscular load, and the muscular load in users with different body sizes can be predicted.
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