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The exact cause of Delayed Onset Muscle Soreness (DOMS) is unknown. It is described as a consequence of mechanical and metabolic stress placed on skeletal muscle fibres. DOMS occurs as a result of microscopic tearing (micro trauma) of the muscle fibres and connective tissues. The extent of the tearing depends on the type of exercise and how vigorously the exercise is performed. Any new movements that a person is not accustomed to, may lead to DOMS. However eccentric muscle contractions seem to cause the most pain. Eccentric muscle movement is any movement that forces the muscle to contract while it lengthens.
Contrary to popular belief, DOMS is not related to the buildup of lactic acid in the muscle that occurs after strenuous exercise. Even though lactic acid is a by-product of muscle metabolism, it is removed within the first hour after exercise and does not contribute to the symptoms of DOMS.
During a workout, the skeletal muscle swells. The swelling is a result of an influx of white blood cells, prostaglandins, nutrients and fluids that flow into the muscle to repair any damage after a strenuous workout. This damage to the muscle occurs in the myofibrils and the influx of fluids is part of the normal process of repair and growth in the body.
Metabolic stress seems to be to most plausible cause of DOMS, but what are these metabolic stresses and are the presence of these molecules necessarily the cause of DOMS? Is it reasonable to believe that the by-products of these cells can be related to the onset of muscle soreness?
There is growing evidence that "free radicals" are a major contributing factor of DOMS. They are an unavoidable by-product of cellular metabolism. These molecules are highly reactive and unstable. The uncertainty of their role comes from the fact that they may not be present in high enough concentrations when DOMS is at its worst. The extreme increase of free radicals seems to occur after the peak decline in muscle function.
A study done on the relationship between dehydration and DOMS, (Cleary, 2005), showed that increased body and muscle temperatures during exercise due to lack of fluid intake and dehydration, play a contributing role in micro trauma to the muscle fibres. The high muscle temperatures and resistance exercise result in the denaturing of proteins, and may affect the mechanical properties of the myofibrils, making them more susceptible to damage during eccentric activity.
Dehydration and hyperthermia of the muscles may also lead to a disruption of the intercellular calcium regulation and overproduction of adenosine triphosphate (ATP), which may also be a contributing factor to the micro-damage during exercise.
Delayed Onset Muscle Soreness (DOMS) can potentially be perceived as a love / hate relationship by many. A love relationship because DOMS can be viewed as a sign that yesterday's workout was rather effective, but a hate relationship because exercising again within the next day or two won't be comfortable. It can turn a simple walk up a flight of stairs into a painful five minute ordeal.
DOMS is a phenomenon experienced by all individuals, no matter their fitness level. If an individual has recently begun exercising, or has just returned to exercising after a long break, they may soon become stiff and sore. This is a normal physiological response to increased exertion on any skeletal muscle.
Characterized by an aching, dull pain in the affected muscle, typical symptoms may include:
Â Muscle tenderness, stiffness and / or soreness (may increase to the level of muscle pain)
Â Localised swelling (may be considered a cause and contributor to soreness)
Â Loss of mobility, reduced range of motion and resistance to stretching
Â Loss of muscle strength
Â Acute muscle spasms and twitches
Symptoms begin to develop 24 - 48 hours after intense, unfamiliar exercise. The intensity of the symptoms will increase for the first 24 hours, reaching their peak within 72 hours. Thereafter they will begin to subside. Five to seven days after exercise, all symptoms should have disappeared. Muscle pain is not felt when the muscle is at rest, but rather when it is stretched, contracted or put under pressure.
Not all symptoms may be present and they are independent of each other. The extent and duration of DOMS may vary from person to person, and the extent of DOMS is often related to the amount of resistance placed on the muscle during the prior exercise.
Theodore Hough was the first to describe Delayed Onset Muscle Soreness in 1902. He described DOMS as "fundamentally the result of ruptures within the muscle". Today this description is still considered broadly valid, but the cellular mechanisms and etiology are still not fully known. New research shows that there are many theories behind the phenomenon of DOMS, none of which have been fully proven or disproved. It has been suggested that the muscle soreness is a result of an acute inflammatory response, but subsequent research failed to substantiate this theory conclusively.
The first theories to emerge attributed DOMS to lactic acid accumulation and oedema of the tissues due to increased hydrogen ions. This is now considered highly unlikely as there is evidence to refute this theory. It has been proven that lactic acid cannot be responsible for the development of muscle spasm and soreness. As stated earlier, it is removed from the muscle within an hour after intense exercise, and soreness only tends to develop 24 hours later.
Soreness does not involve the rupture of whole muscle fibres. DOMS results from high tension in the contractile / elastic system in muscles from eccentric exercise. This tension causes the muscle fibres (myofibrils) and connective tissue to become structurally damaged or torn. Damage normally occurs from the ultrastructural disruptions of myofilaments at the z-line, a line that marks the boundary of adjacent sarcomeres. This leads to an imbalance of calcium levels and necrosis of damaged cells and surrounding tissue.
Tissue damage and necrosis may be most directly related to the soreness that is experienced. Pain is experienced when the muscle is stretched or palpated because of the increased mechanical sensitivity of nociceptors. The onset of soreness is delayed because the mild inflammatory response that does result from nocioceptor sensitization, is a slow process.
The relationship between damage, inflammation and soreness is not yet completely understood, and the most accepted clinical correlates associate DOMS with elevated plasma enzymes, myoglobinemia, and abnormal skeletal muscle histology.
Although not fully proven, this theory is most often used to explain the relationship between the symptoms of DOMS and the mechanisms behind it.
Â High tensions in the contractile / elastic system of the muscle result in structural damage.
Â Cell membrane damage leads to disruption of calcium homeostasis causing necrosis that peaks between 24 - 48 hours after exercise.
Â Products of macrophage activity and intracellular contents accumulate in the interstitial fluid These stimulate the free nerve endings of sensory neurons in the muscles leading to the sensation of DOMS.
I. Mechanical Damage II. Inflammation & Swelling III. Free Radical Proliferation
Phospholipase A2 activation
Injury to muscle membrane
Figure 1: Schematic showing the possible mechanisms and sequence of injury of DOMS (Treatment and Prevention of DOMS - Declan A.J. et al) 5
A significantly effective treatment method has not yet been established to accelerate the recovery from DOMS. A variety of treatment strategies may assist in alleviating the symptoms and severity of DOMS.
Non-steroidal anti-inflammatory drugs (NSAIDs), such as aspirin and ibuprofen, appear to moderately inhibit the inflammatory response and thereby provide pain relief. It has, however, no positive effect on the muscle weakness associated with DOMS. The regular use of NSAIDs could also lead to adverse side effects, primarily upper gastrointestinal ulceration or bleeding due to mucosal damage.
Homeopathy is a safe, natural treatment method with very few side effects. Traumeel is an effective homeopathic preparation used as an alternative to NSAIDs for the treatment of inflammatory conditions brought on by exercise-induced micro trauma and other sports injuries. In a double blind clinical trial involving 50 athletes, Jordaan (2005) tested certain inflammation markers such as serum creatine kinase, differential white blood cell levels and serum cortisol. The treatment group showed higher levels of plasma cortisol than the placebo group for up to 96 hours post exercise. Cortisol, a glucocorticoid, will have an anti-inflammatory effect and also slow the migration of phagocytic cells into the area. This effect was illustrated by a significantly lower mean monocyte count in the treatment group in the first 96 hours after exercise, implying reduced macrophage activity. Arnica is another homeopathic remedy that is often used in the treatment of DOMS, but both oral and topical administration of Arnica has so far proven ineffective under clinical trial conditions.
Acupuncture and dry needling have also been suggested as an effective treatment for DOMS. Studies show that the best results are achieved when the acupuncture needles are applied directly to the tender points. According to Robertshawe (2009), acupuncture is effective in reducing the perception of pain, but had no significant effect on participant's mechanical pain threshold or muscle function after DOMS had been induced.
Â Therapeutic massage stimulates blood circulation to promote healing and repair. Massage has no effect on the improvement of muscle function, except to reduce muscle soreness and oedema.
Â Cryotherapy (icing) of the injured muscle seems to be the most effective way of reducing muscle pain related to DOMS.
Â Ultrasound and electrical current modalities has demonstrated little effectiveness in the reduction of symptoms.
Â Hyperbaric Oxygen therapy, (supersaturating the blood with O2), decreases the healing time of the damaged muscle fibres and connective tissue. Increasing blood oxygen levels leads to improved blood circulation, healing and repair.
Â Light exercise with reduced eccentric movements, have an analgesic effect for the temporary relief of pain.
Â Gentle stretching has been proven to have little effect on muscle pain, but many athletes have claimed that it simply makes them "feel better".
Â Research has emerged that Vitamin C plays a role in the repair of connective tissue, however this has not yet been proven in any clinical trials.
Â The use of anti-oxidants prior to exercise, in a fight against the free radical by-products of cellular metabolism, can reduce and possibility prevent DOMS.
Â Protease supplements have proved to be effective in the prevention and recovery of DOMS. Supplementation may facilitate muscle healing and promote restoration of contractile function. An experimental group demonstrated significantly superior recovery of contractile function and diminished effects of DOMS.
Any muscle injury needs rest for the muscle fibres to heal effectively. Most treatment strategies do not promote rapid healing of the damaged tissue, even though they do alleviate the muscle soreness and pain. Exercise-induced muscle damage is a normal response; muscles attempt to protect themselves against repeated exercise sessions, to avoid serious tissue damage.
It would appear that even though there are numerous therapies and treatments that are effective in reducing some of the symptoms of DOMS, none of them are able to completely alleviate all of the symptoms or successfully prevent the occurrence of DOMS. Until all the mechanisms of DOMS are better understood, the best cure would be prevention of DOMS by gradual introduction of novel exercise, especially after long periods of inactivity. 6