A one arm push up is a compound exercise that requires far more strength and balance than a standard push up using two arms. To perform the exercise, the athlete starts in a plank position but supports himself or herself with only one arm. The athlete then lowers the body toward the ground, then pushes it back up again. This exercise primarily strengthens the chest and triceps muscles. It also benefits the stabilizer muscles in the arms, chest and abdomen, and it provides a slight benefit for the legs.
There are two variations of the one arm push up. The first and most common is a one arm push up with the arm out. In this variation, the arm that is performing the push up will be farther away from the body than it would be in a standard push up. It is not directly underneath the body, so it will provide less support for the upper torso. To counteract this, the legs will be much wider than shoulder width apart.
With the legs in this position there will be a tension that runs from the supporting arm through the body and into the opposite leg. The other leg helps to provide balance, but the opposite leg and hand will support most of the weight during the one arm push up. Feeling this tension is crucial because it is the athlete's ability to use his or her arm and opposite leg to counteract this tension that will provide the necessary balance to perform the exercise.
Once an athlete achieves this balance, he or she can bend the arm to lower the body toward the floor. Once the chest is close to the floor, the athlete pushes with the arm to raise the body back to the original position. The athlete can then repeat the process for any number of repetitions before switching to the other arm.
The other variation of the one arm push up is to keep the arm close to the body in a manner that is similar to a two arm push up. This will allow the legs be closer together, too. The tension between the arm and the opposite leg will still exist. The legs are closer together, though, so they do not combine with the hand to form as broad of a triangle as they did in the previous variation. As a result, the balancing leg is not able to help the athlete's balance as much.
The result is that this version of the one arm push up is more difficult than the arm-out version. Both variations work the same muscles, but the stabilizing muscles in the arm-in variation have to work a lot harder. Both versions, though, provide a far more intense workout than two arm push ups, because the individual arm essentially has to push twice as much weight.