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Muscle Soreness After Exercise

What causes sore muscles after exercise and sports activities?

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Updated May 31, 2014

The condition known as delayed onset muscle soreness (DOMS) is a common complaint of many athletes. Muscle soreness after exercise has been extensively studied, but even now, the exact cause of sore muscles is not perfectly understood. Furthermore, many of the commonly recommended treatments for muscle soreness after exercise has not been shown in scientific studies to be terribly effective in relieving symptoms.

What Causes Sore Muscles After Exercise?

The cause of muscle soreness after exercise is not precisely understood. While injury to the muscle occurs as a result of repetitive and strenuous use, the exact cause of muscle pain is still being investigated.

Muscle soreness associated with exercise is thought to be most significantly related to inflammation within the muscle. We know that damage to the muscle fibers does not itself create the pain of sore muscles. There are hereditary conditions that cause muscle damage (such as muscular dystrophy), but do not cause muscle pain. Therefore, the cause of exercise-related muscle soreness is thought to be due to the inflammation that is the result of muscle damage.

When the muscle fibers are stretched too far, and stretched repeatedly, small tears called "microtears" can occur within the muscle fibers. When these tears occur, the injured muscle releases various substances that stimulate an inflammatory response. These "inflammatory mediators" are useful in creating a healing response, but also cause painful symptoms experienced as muscle soreness. While this may not be the only cause of sore muscles, it is thought to be a major contributor.

Do certain types of exercise tend to cause sore muscles?
The most frequent cause of muscle soreness after exercise is related to activities that cause repetitive eccentric contractions of the muscle. An eccentric contraction occurs when the muscle is contracting but being lengthened by another force. Some activities that often involve eccentric contractions include certain types of weight-lifting and running/hiking downhill. Activities that involve eccentric contractions of the muscle have a much higher rate of athletes developing muscle soreness.

What are the symptoms of muscle soreness?
The typical symptoms of delayed onset muscle soreness develop about 24 to 48 hours after the exercise activity. The common symptoms include:

  • Aching pain
  • Muscle stiffness
  • Tenderness of the muscle
The symptoms of muscle soreness usually peak after about 3 days and gradually taper off. Most athletes with muscle soreness will get back to normal within 5 to 7 days, even with no specific treatment.

What treatments can help sore muscles?
The best and most reliable treatment is allowing time to pass, and the body will heal itself. As stated, most people are completely back to normal within 5 to 7 days from the activity that caused the muscle soreness. The treatment of sore muscles is controversial, because most treatments have been shown to provide little, if any, benefit in large studies. That said, many athletes swear by certain treatments they have found beneficial. Whether or not these athletes would have improved with simple rest is difficult to say, but we do know that most treatments for sore muscles are not harmful, and therefore reasonable to try.

Can muscle soreness after exercise be prevented?
Muscles learn to adapt to the forces that are exerted by the body. Therefore, the best prevention of delayed onset muscle soreness is a gradual buildup whenever starting a new sport or exercise routine. Sudden increases in intensity or duration of activity can increase the chance of developing sore muscles.

Many people advocate stretching to prevent the problem of sore muscles. Unfortunately, scientific studies have failed to show any benefit of stretching in the prevention of muscle soreness. While stretching has not been shown to increase the chance of developing muscle soreness, it probably has little effect in preventing the problem.

Sources:

Lieber RL, Fridén J "Morphologic and Mechanical Basis of Delayed-Onset Muscle Soreness" J. Am. Acad. Ortho. Surg., January/February 2002; 10: 67 - 73.

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