INTRODUCTION

Today, exercise has become more important and prevalent in the daily routine of Americans. Different types of work-out routines result in different benefits to the individual. Push-ups are a common type of exercise that do not require the use of any exercise equipment; this means that it can be done virtually anywhere. Push-ups are an excellent exercise to strengthen the upper body because they are safe, effective, and require the action of several muscle groups to be performed properly. Push-ups are performed in a prone position, using only the hands and toes to support the body weight. While in this position, the individual pushes off the floor with the hands to lift their body, maintaining a straight line between the shoulders, hips, and feet. Once full elbow extension is reached, the individual then slowly lowers themselves to the floor.

When performing a push-up, the horizontal adductors and the elbow extensors will be active throughout both the ascent and descent of the push-up. During the ascent phase, these muscles must work against gravity in order to produce elbow extension and horizontal adduction of the shoulder. During the descent phase, gravity works in the same direction as the movement. Because gravity applies a flexor torque on the elbow and a horizontal abductor torque on the shoulder, the muscle torques must be applied in the opposite directions. This means that the elbow extensors and shoulder horizontal adductors must contract in order to produce a controlled lowering of the body during the descent phase.

Performing a push-up requires the use of various chest, back, shoulder, and upper arm muscles- including the elbow extensors and the shoulder horizontal adductors, working concentrically and eccentrically. Varying the hand placement when doing push-ups produces distinct differences in joint and muscle loads. By looking at the two types of push-ups, without looking at the data, we can see that the relative joint angles of the shoulder and elbow differ between the close-hands and far-hands push-up. Because the relative angles will be different between the two types of push-ups, we can infer that the muscles will be active through different ranges of motion. Our group is interested in studying how the hand position affects the performance of a push-up. We will compare the kinematics between two different push-ups: a push-up with the hands positioned closely together (close-hands), and a push-up with the hands positioned farther apart (far-hands). We aim to answer several questions: How are the joint angles and ranges of motion different between the two push-ups? What type of implications might these differences have on muscle strength development?