Abstract: Locations of a person's hand, shoulder and hip in three-dimensional space are received from a three-dimensional position sensing device. A shortest distance from the location of the person's hand to a line between the location of the person's shoulder and the location of the person's hip is determined. The shortest distance is compared to a threshold to determine if the person is overreaching. When it is determined that the person is overreaching, a user interface is provided to indicate that the person was overreaching. Additional location information for points on the person's body are used to determine if the person is performing a high lift, a low reach or a twist.