Exercise substitutions are required when you do not have the necessary equipment, when you want a variation or if you cannot safely perform the recommended exercise. If any of these reasons, or more, have you replacing your bench press with the pushup, you're on the right track -- but keep in mind certain considerations to reach your training goals.
A pushup is a calisthenic exercise. It is performed in a face-down position. Your hands and feet are on the ground with your body in a straight line. You bend and straighten your elbows to raise and lower your body. The bench press is a free-weight exercise. It is performed in a face-up position with your back on a weight bench and your hands on a barbell. You bend and straighten your elbows as you raise and lower the barbell.
Whether you are in a face-down, or face-up position, the movement of the arms during the pushup and the bench press are similar: your elbows bend to approximately 90-degree angles. The muscles used to do this movement are the pectorals, deltoids and triceps, which are the chest, shoulders and the backs of the upper arms. The joint movements are also the same in the elbows and the shoulders. Therefore, the pushup can replace the bench press during your workout.
A main difference between the pushup and bench press is your body position. During the pushup, your core engages to keep you in a straight line, also known as a plank position. The muscles of your abdomen, your back and your hips contract to maintain the pushup position. Compare this to the bench press in which your body weight is supported by the weight bench so the concentration is in your upper-body muscles. You build muscle tissue in more than just your upper body during the pushup, yet your effort is divided between the upper-body and the core, so the chest is not able to lift as much weight.
The amount of weight moved during a pushup is also limited by your body weight. If your goal is to bench press more than your weight, you need to advance the challenge of the pushup when using it as a replacement exercise. You do this by using pushup variations such as placing your hands higher than your feet or placing your feet higher than your hands. A single-arm pushup is another way to increase the workout challenge.
The pushup can replace the bench press during your strength-training workouts and is a nice option for an outdoor workout. Another reason to use the pushup in place of the bench press is when you are recovering from a shoulder injury. You have more control over the pushup and can limit your range of motion and adjust the resistance by placing your knees on the floor. With the bench press, gravity pulls down the bar toward your chest, which places stress on the shoulder.