muscle soreness

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The muscles of exercisers often become sore. There are two main types of muscle soreness: acute muscle soreness and delayed onset muscle soreness.

Acute muscle soreness develops during and immediately after exercise. It is thought to be due to an inadequate blood flow to active muscle, resulting in the accumulation of metabolic waste products such as lactic acid.

Delayed onset muscle soreness (DOMS) develops one or two days after the completion of exercise. The discomfort associated with DOMS may be due to torn muscle fibres or muscle spasms but is most likely to be due to disruption of the connective tissue. DOMS is usually accompanied by increased levels of hydroxyproline in the urine. Hydroxyproline is a chemical similar to an amino acid and is found only in connective tissue. Its presence in the urine is, therefore, an indication of tissue damage.

DOMS typically affects those who only exercise occasionally or who perform strenuous exercises to which they are unaccustomed. It is greatest following activities that use mainly eccentric contractions in which the muscle lengthens (such as running downhill). Treatment consists of rest and nonsteroidal anti-inflammatory drugs (NSAIDS), such as aspirin or ibuprofen, to relieve the pain. The degree of muscle soreness is correlated to the amount of tissue damage. Therefore, the greater the muscle soreness after an activity, the longer the recovery time required. Slight discomfort may require only a few extra days rest, but severe pain that makes walking difficult may require a month or more of reduced training. Of course, if symptoms persist, medical advice should be sought.

Pain and tenderness in a muscle that typically occurs after strenuous exercise, particularly if the exercise involved eccentric muscle actions. The underlying cause of muscle soreness is thought to be a change in the ultra-structure of muscle cells, with a rupture of the Z-line. Metabolic waste products, such as lactic acid, have also been implicated because they can stimulate pain receptors in the cell. Muscle soreness may occur during and immediately after exercise (see acute muscle soreness) or some time after exercise has ceased (see delayed onset muscle soreness).