Push-up

A push-up (or press-up) is a common calisthenics exercise performed in a prone position by raising and lowering the body using the arms. Push-ups exercise the pectoral muscles, triceps, and anterior deltoids, with ancillary benefits to the rest of the deltoids, serratus anterior, coracobrachialis and the midsection as a whole. Push-ups are a basic exercise used in civilian athletic training or physical education and commonly in military physical training. They are also a common form of punishment used in the military, school sport, or in some martial arts disciplines.

In the past this movement was called a floor dip.

The American English term push-up was first used between 1905 and 1910, while the British press-up was first recorded between 1945 and 1950.

According the study published in Journal of Strength and Conditioning Research, the test subjects supported with their hands, on average, 69.16% of their body mass in the up position, and 75.04% in the down position during the traditional push-ups. In modified push-ups, where knees are used as the pivot point, subjects supported 53.56% and 61.80% of their body mass in up and down positions, respectively.

While the push-up primarily targets the muscles of the chest, arms, and shoulders, support required from other muscles results in a wider range of muscles integrated into the exercise.

The rectus abdominis and transversus abdominis contract continually while performing push-ups to hold the body off the floor and keep the legs and torso aligned. The rectus abdominis spans the front of the abdomen and is the most prominent of the abdominal muscles. The transversus abdominis lies deep within the abdomen, wrapping around the entire abdominal area. Both muscles compress the abdomen, and the rectus abdominis also flexes the spine forward, although it does not execute this function when performing push-ups.

...
Wikipedia