The primary cause of muscle soreness after a new workout is delayed onset muscle soreness (DOMS), which typically occurs 24 to 72 hours post-exercise. This soreness is a result of tiny muscle tears that occur during intense or unfamiliar physical activities. The body responds through an inflammatory process, leading to muscle repair and adaptation. While soreness can be uncomfortable, it signifies muscle growth and strength adaptation. Gradually increasing workout intensity can help minimize DOMS and enhance the body’s ability to recover, paving the way for improved fitness levels.