Why is my chest sore after doing push-ups?

Your chest may be sore after doing push-ups because the exercise puts stress on the muscles in your chest, causing tiny tears in the muscle fibers. This is a normal part of the muscle-building process, and the soreness is known as delayed onset muscle soreness (DOMS). It typically occurs 24-48 hours after exercise and is a sign that your muscles are repairing and getting stronger.