If you overdo training, you may experience soreness 24 hours later. According to current thinking, this delayed-onset muscle soreness (DOMS) has several possible causes: slight tears in connective tissue, damage to muscle fiber, accumulation of fluid (edema), uncontrolled contractions of muscle fibers, or lingering effects of metabolic by-products—though not, contrary to what many think, lactic acid, which is eliminated within an hour after your workout. And we know that exercise involving eccentric contraction—as in downhill running or lowering a heavy weight—is more likely to cause soreness that persists for days and reduces your enjoyment of subsequent activity.
You can minimize soreness by practicing patience. Avoid maximal lifting; instead, begin with light weights and progress gradually. Also steer clear of all-out running and ballistic movements such as hard throwing when you begin or renew an activity. At the same time, since experience shows that we are seldom patient enough, we also need a way to reduce soreness, and stretching has been shown to reduce muscle discomfort. It is worth your while to stretch before and after exercise, or anytime that you feel tight or sore.
If your muscles are sore, you may experience reduced strength for as long as 2 weeks. You’ll find that you recover faster and have less soreness after successive bouts of exercise. Fortunately, DOMS occurs only during the start-up phase, and the symptoms disappear within a few weeks, reappearing only after a long layoff or the vigorous start of a new activity. Indeed, exercise-induced muscle soreness seems to inoculate the body against subsequent discomfort for up to 6 months following the initial soreness.