The height of the seat and the footrest is a mutually coordinated relationship, such as the seat is high, the footrest is relatively low, and vice versa, the footrest is high. In general, the disabled person sitting in a wheelchair with both lower limbs on the pedals, the lower thighs in the front 1/3 above the front edge of the cushion about 4 cm, about 2 fingers wide. If the seat is too high or the footrest is too low, it will cause both lower limbs to lose support, and the lower limbs will hang in the air, and the body will not be able to maintain balance. On the contrary, if the seat is too low or the footrest is too high, it will make the hip bear all the gravity, causing discomfort to the disabled and damage to the soft tissues of the hip for a long time, and at the same time, the disabled will struggle to operate the wheelchair. There is a third undesirable situation, that is, the seat and footrest are too high or too low at the same time, which will increase the difficulties of the disabled in operating the wheelchair, the former is the wheelchair can not be close to the desktop, affecting the functional activities, the latter is easy to collide with the ground, so that the action is obstructed.