DOMS

Sore muscles after physical activity, known as delayed onset muscle soreness (DOMS), can occur when you start a new exercise program, change your exercise routine, or increase the duration or intensity of your regular workout.

Delayed onset muscle soreness (DOMS) is the pain and stiffness felt in muscles several hours to days after unaccustomed or strenuous exercise. The soreness is felt most strongly 24 to 72 hours after the exercise.

Theo: How are you so weak? I thought you go to the gym.
Nicholas: I do go to the gym! I just have DOMS.