Performance
A huge aspect for ski boot design is the ergonomics of the body. During a turn, the boot can experience loads at 150% of the body weight of a person. Getting the person to exhibit proper posture and form while skiing is very important for injury prevention.

This is a diagram of the knee. When a person's knee is bent too far forwards, a downward force from the body (F1 and F2) is greatly exasperated by too much bend (T1 and T2). If the force is too great, and injury will occur.