When starting any new workout program it is normal for your muscles to feel stiff or sore within the first day or so after exercising. This soreness is called Delayed Onset Muscle Soreness or D.O.M.S. D.O.M.S. is believed to be the result of tiny tears in the muscle or connective tissue. When your body is adjusting to a new activity, and your muscles are being used in new and wonderful ways some degree of D.O.M.S is to be expected. Stiffness, soreness or pain in muscles or joints deserves a rest for 24-48 hours. Resting muscles prevents injury and allows muscles to repair themselves.