When unclassified, a muscle strain usually refers to a relatively minor injury in which muscle fibres are damaged, but there is little if any rupture of blood capillaries. However, a strain is usually classified as a first, second, or third degree strain according to the severity of damage to the muscle. A first degree strain refers to tearing of less than 25% of the muscle fibres the muscle is tender, but there is usually no impairment of muscle action. A second degree strain refers to tearing of between 25 and 75% of the fibres, usually accompanied by swelling and bruising, and some limitation of muscle mobility. A third degree strain refers to a complete rupture of the fibres with the muscle being completely torn in two; it is accompanied by extreme tenderness, severe bruising (see haematoma) and impairment of movement. Rest, ice, compression, and elevation (see RICE) is the cornerstone of primary treatment. Ice should be applied immediately after the injury (see ice treatment). A doctor should be consulted if function is impaired. Mild and moderate strains often benefit from light stretching within the pain threshold. Strains, tears, and ruptures most commonly affect those muscles, such as the hamstrings, which span two joints (see Lombard's paradox). They occur most often in cold weather when joints are stiff and coordination is impaired by nerve conduction being slow. Wearing suitable clothes and warming-up adequately can reduce the risk of muscle strains. See also muscle soreness.
Subjects: Sports and Exercise Medicine.