Usually, the muscles ache for about 48 hours. Then, athletes exercise less intensely the next few days, until their muscles stop aching. Exercising intensely when muscles ache causes injuries and decreases performance, whereas waiting for the muscles to stop aching before exercising intensely again strengthens muscles. Two types of muscle discomfort may be felt after exercise. On the other hand, the pain of injury is usually felt soon after it occurs, is worse on one side of the body, does not disappear 48 hours later, and becomes much more severe if a person tries to exercise.
Warm muscles are more pliable and less likely to tear than cold muscles, which contract sluggishly.
Going through the motions increases blood flow to the muscles that will be used, warming them up and readying them for more vigorous exercise. Blood flow must increase substantially to protect the muscles from injury during exercise. Stretching A person should stretch only after warming up or exercising, when the muscles are warm and less likely to tear. Stretching lengthens muscles and tendons, and longer muscles can generate more force around joints, helping a person jump higher, lift heavier weights, run faster, and throw farther. There's scant evidence that stretching prevents injuries or delayed-onset muscle soreness, which is caused by muscle fiber damage.