Although the saying "no pain, no gain" is as outdated as leg warmers and disco, most people have some sort of muscle soreness at some point in their workout careers. Although soreness can be a real pain in the neck, butt, back, shoulders or legs, it's usually nothing to be concerned about.

There are two kinds of exercise-related muscle soreness: One that occurs during or immediately after exercise and one that occurs several hours or even days after a harder-than-usual workout.

Muscle soreness during and immediately after exercise is caused by buildup of a chemical called lactic acid, a natural byproduct of your body's energy-producing mechanisms. When you push yourself to your limit, lactic acid floods your muscles, causing pain, soreness, and discomfort -- your body's way of telling you to stop now. This type of soreness subsides after a minute or two of rest, and you can usually continue exercising without any residual effects.

The other kind of soreness is called delayed-onset muscle soreness, or DOMS for short. Microscopic tearing of muscle fibers appears to be the culprit that causes DOMS, although scientists aren't exactly sure why your muscles have this delayed reaction. The amount of tearing depends on how hard and how long you've exercised and what type of exercise you did. The soreness is generally at its worst within the first two days after an extra effort workout and subsides within a few days.

When you experience DOMS, stretching and ice may be your fastest forms of relief. Slow, steady stretching of your sore spots helps increase blood flow to the area, speeds the healing process and reduces the localized stiffness that make moving a painful proposition. Ice numbs the pain and signals your circulatory system to whisk away any waste products that flood into those microtears (thought to be another contributor to DOMS). You might also think about getting a massage. Massage reduces soreness and allows you to work out closer to an optimal level the next day. And besides, as we told you last week, a massage feels so good that it can help you forget about any ache and pain you have.