The concept of a pushup is simple. You place your hands and feet on the floor and raise and lower your body by bending your elbows. The exercise is not easy, as your body weight provides resistance, and it sounds more difficult when you discover how many muscles you are using and the different types of contractions these muscles produce.
The pushup is an upper-body strengthening exercise. The muscles of your chest, shoulders and arms push your body away from the floor, and they also contract to slowly lower your body so you do not fall quickly and land on your face. In addition to the muscles that move during the pushup, your body uses muscles that are tight and remain contracted throughout the entire movement. For example, if you don't contract the muscles of your core, your back will not stay straight.
The Way Down
The downward phase of a pushup focuses on eccentric muscle contractions. An eccentric contraction occurs in the same direction as the pull of gravity. The eccentric contractions of your chest, shoulders and triceps in the back of your upper arms support the elbow movement that is slow and controlled as you lower your body. Another way to identify an eccentric muscle is that it exerts force, but it lengthens instead of shortens.
Pick It Up
The upward phase of a pushup uses muscles concentrically. Concentric contractions occur in the direction opposite the pull of gravity: The chest, shoulders and triceps shorten as they contract to straighten your arms and push you away from the floor. The pushup targets the muscles of your chest and uses the assistance of your shoulders and triceps.
Muscle contractions also occur apart from the arm movement in a pushup. These are known as isometric contractions. The muscles are tensioned and exert force, but do not change in length. The muscles of your core, including your rectus abdominis and obliques, isometrically contract during a pushup. The erector spinae along both sides of your spine also statically contracts, as do the quadriceps to support your straight body position.
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