Delayed onset muscle soreness

If you have ever trained with weights before or especially if you are just starting out, you may (or soon will) know about the common phenomenon of delayed-onset muscle soreness (DOMS). DOMS is the scientific term for not being able to move the day of or the day after a weight-training session. You might have difficulty just getting out of bed, and all day long you'll be walking as if you just got off a horse (if you can walk at all). You might even regret ever setting foot in the gym. Why do muscles get so sore when you first embark on a weight-training program, or after long layoffs, new exercises, or heavy workouts? Experts continue to debate the exact whys and hows of muscle soreness, but theories abound.

DOMS affects muscular performance temporarily because of both a voluntary reduction of effort (since the muscles are too sore to move) and an actual loss of the muscle's ability to produce force. Many studies have shown that strenuous and unaccustomed exercise damages muscle cells. Some studies have shown that eccentric exercises, in which muscles lengthen as they exert a force (as when slowly lowering a weight), cause more muscular damage than concentric exercises that shorten the muscle (as when lifting a weight). The extent of injury seems to be related more to the change in muscular length than to the force generated by the muscle. The high tension associated with eccentric exercise disrupts the muscle cell membrane. Extracellular calcium then enters the muscle cell and disturbs the delicate balance of electrolytes. This process results in tissue damage that peaks about two days postexercise. When tissue damage occurs, inflammatory cells called neutrophils infiltrate the muscle and cause inflammation. More inflammatory cells called macrophages move in to clean up and remove the cellular debris. A second wave of macrophages then comes in to assist the repair procedure, along with stress proteins. Inflammation is a necessary process in the healing of tissue. As the inflammatory process runs its course, muscle fibers are repaired and become stronger. As the muscle becomes stronger, this process may even prevent subsequent damage.

A popular theory, now refuted, was that DOMS was caused by lactic acid that accumulated in muscles after strenuous exercise. Research has now shown that lactic acid dissipates quickly and that eccentric exercise produces less lactic acid than concentric exercise.

Scientists do not know the exact reason for the pain associated with DOMS, but many hypotheses try to explain the phenomenon. One theory is that inflamed and swollen muscle fibers press on pain receptors and alert the brain to register pain. Another theory suggests that the inflammatory cells (phagocytes) that come to clean up the damaged tissue further damage the tissue, which leads to pain. Still another theory surmises that the free radicals (molecules that are highly reactive and harmful in the body) produced by the inflammatory cells aggravate the already existing damage, causing pain. Most likely a combination of all these factors contributes to the pain of DOMS.

We know that DOMS results in pain and stiffness, loss of muscular strength, loss of the ability to generate force, and an increase in muscular fatigue. But a significant, overlooked fact is that the damage from DOMS prevents proteins that transport glycogen from entering the muscle. This phenomenon results in an impairment of glycogen resynthesis, which is crucial to muscle development. Glycogen is the energy the muscle uses to work and grow. When it is depleted after exercise, it is difficult for the muscle to heal and to store up energy for its next work assignment. Excessive eccentric exercise also impairs muscle pH regulation and cellular function.

Although the pain from DOMS may have something to do with inflammation, many studies have shown that common anti-inflammatory medications taken before and after eccentric exercise do not decrease that pain. It is possible that the soreness is not entirely related to the inflammation, or that the inflammation seen in DOMS is not the typical inflammation seen in other types of muscular injuries. Regardless, it seems that taking anti-inflammatory medications may be harmful to the healing process and possibly even delay it. The same advice goes for massage. Currently there is little scientific evidence that massage can help decrease pain or increase function after DOMS-likewise with ultrasound, electrical stimulation, and ice.

How can you avoid DOMS in your training program? The most important step you can take is to have a specific training plan and gradually acclimate to exercises and weights. Don't take up where you last started if you have been away from the gym for some time. Likewise, if you have never trained with weights, starting slowly with light weights is more appropriate for muscular and joint health than moving quickly with heavy weights. Make sure that you get sufficient rest and recovery time. Muscles can get slightly damaged from weight training, and there is always an eccentric component. Waiting at least 48 hours between weight sessions for the same muscle group, or until the pain is gone, is appropriate. Also, limit your use of prolonged eccentric contractions. If you make yourself so sore that you don't want to strength train anymore, you only succeed in demotivating yourself.