INTRODUCTION

Everyday millions of parents injure their backs by simply picking up their children. As mentioned in, "Back Pain and Parenthood," parenthood is a risk factor for back pain (Finkelstein, 1995). Considering the harmful repetitive lifting that goes along with care- giving, this doesn't come as a surprise (Dolan and Adams, 1998). The most efficient way to reduce this risk of back pain would be to use a lifting technique that produces the least amount of strain on the back. What is this position that induces minimal strain while lifting a child?

The purpose of this motion study was to compare and analyze the biomechanical differences that occur in the torso angle, shoulder joint, hip joint and the center of mass-to-hip moment arm when performing a stooping vs. squatting lift. The two motions we chose for the comparison are commonly performed motions. We defined the stoop motion as bending at the waist and not bending at the knee. Squat, we defined as bending at both the knee and waist. A digital analysis was done for the key body joints and segments during these motions. The shoulder joint was examined to confirm the position of the subject while performing the lift. The trunk angle and hip joint were analyzed to determine the impact of the lifting kinematics. The length of the center of mass-to-hip moment arm is important because it was a key factor in determining how much force was actually being applied to the strain area. We predict this moment arm will be the longest for the stoop lift, and it is this difference between the movements that will make the stoop lift the most detrimental.