Push-ups train chest, shoulders, and trunk stiffness with no equipment. They also teach the bracing that heavy squats and hinges borrow.

Diagrams show the shape of the movement. Follow the written steps before you add load.
Equipment. Bodyweight
Muscles. chest. Also shoulders, triceps, core
All Cheeked Up publishes general fitness education. It is not medical advice, physical therapy, or a promise that your body will change. Stop any exercise that causes pain and talk with a qualified professional about injuries, pregnancy, or health conditions before you train.