Johndavid Maes, and Len Kravitz, Ph.D.
Delayed onset muscle soreness (DOMS) is a phenomenon that has long been associated with increased physical exertion. DOMS is typically experienced by all individuals regardless of fitness level, and is a normal physiological response to increased exertion, and the introduction of unfamiliar physical activities. Due to the sensation of pain and discomfort, which can impair physical training and performance, prevention and treatment of DOMS is of great concern to coaches, trainers, and therapists. In a recent review, Szymanski (2001) provides an extensive evaluation of the mechanisms and treatments for DOMS. Although science has not established a sound and consistent treatment for DOMS, previous interventions include pharmaceuticals, pre-exercise warm-up, stretching, massage, and nutritional supplements, just to name a few. The pain and discomfort associated with DOMS typically peaks 24-48 hours after an exercise bout, and resolves within 96 hours. Generally, an increased perception of soreness occurs with greater intensity and a higher degree of unfamiliar activities. Other factors, which play a role in DOMS, are muscle stiffness, contraction velocity, fatigue, and angle of contraction. In order to minimize symptoms and optimize productivity in a physical training program it is vital to understand the proposed mechanisms of injury, which occur in DOMS. In another recent review, Connolly, Sayers, and McHugh (2003) present an explanation for the mechanisms of injury, as well as various modalities for prevention and treatment of DOMS. The purpose of this article is to provide a review of the mechanisms of injury associated with DOMS as well as an evaluation of the recommendations of various proposed treatments.
MECHANISMS of INJURY
For many years the phenomenon of DOMS has been attributed to the buildup of lactate in the muscles after an intense workout. However, this assumption has been shown to be unrelated to DOMS. The perceptions of pain and soreness that result from intense eccentric exercise are not related to lactate buildup at all. Szymanski’s review (2001) notes that blood and muscle lactate levels do rise considerably during intense eccentric and concentric exercise, however values for blood and muscle lactate return to normal within 30-60 minutes post exercise. Szymanski also notes that concentric exercise produces two-thirds more lactate than does eccentric exercise. If DOMS was brought on by the accumulation of lactate in the muscles, there would me more of an incidence of DOMS after concentric exercise than that of eccentric exercise. Furthermore, blood lactate levels drop to normal values within 60 minutes of an intense exercise bout. The symptoms of DOMS peak within 24-48 hours after an intense eccentric exercise bout when blood lactate levels have been at normal levels for a considerable amount of time.
DOMS is often precipitated predominantly by eccentric exercise, such as downhill running, plyometrics, and resistance training. In their review, Connolly et al. (2003) explain that the injury itself is a result of eccentric exercise, causing damage to the muscle cell membrane, which sets off an inflammatory response. This inflammatory response leads to the formation of metabolic waste products, which act as a chemical stimulus to the nerve endings that directly cause a sensation of pain. These metabolic waste products also increase vascular permeability and attract neutrophils (a type of white blood cell) to the site of injury. Once at the site of injury, neutrophils generate free radicals (molecules with unshared electrons), which can further damage the cell membrane. Swelling is also a common occurrence at the site of membrane injury, and can lead to additional sensations of pain. Connolly et al. also note the importance of differentiating DOMS from other injuries such as muscle strains. This difference is important to appreciate because when muscle strain is sustained from vigorous exercise, particularly eccentric exercise, it can severely worsen the injury. In contrast, in a muscle that is experiencing DOMS, continued eccentric exercise is still possible without further muscle damage. When dealing with DOMS it is important to differentiate it from muscle strains, recognizing that continued exercise is still possible with DOMS, but not with muscle strain.
Symptoms Associated With DOMS
Both Connolly et al.(2003) and Szymanski (2001) agree that typical symptoms often associated with DOMS include strength loss, pain, muscle tenderness, stiffness, and swelling. Loss of strength usually peaks within the first 48 hours of an exercise bout, with full recovery taking up to 5 days. Pain and tenderness peak within 1-3 days after exercise and typically subside within 7 days. Stiffness and swelling can peak 3-4 days after exercise and will usually resolve within 10 days. It is important to note that these symptoms are not dependant on one another and do not always present at the same time.
Although there has been a considerable amount of research on the treatment of DOMS, to date no one treatment has proved dominant in consistently preventing or treating DOMS. Among popular interventions are pharmacological treatments using non-steroidal anti-inflammatory drugs (NSAIDs), therapeutic treatments utilizing physical modalities such as stretching and warm-up, and interventions using nutritional supplements. The following is a discussion and evaluation of these proposed mechanisms of treatment and the prevention of DOMS.
Benefits of NSAIDs
Nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin, ibuprofen, and flurbiprofen have long been considered as a treatment for alleviating the symptoms of DOMS. Theoretically, NSAIDs have a strong case for helping to combat the inflammation and swelling which occurs with exercise induced muscle damage. Despite this strong theoretical backing, research done on the effectiveness of NSAIDs has provided mixed and conflicting results. Due to inconsistencies among studies between type, dose, and timing of various NSAIDs, as well as associated negative side effects such as gastrointestinal distress, and hypertensive effects, NSAIDs do not appear to be an optimal choice for treatment of DOMS.
Benefits of Nutritional Supplementation
Nutritional supplements have also emerged as a potential treatment for DOMS. Anti-oxidant’s, such as vitamins C and E, are known to reduce the proliferation of free radicals, which are thought to be generated during the inflammatory response potentially causing more damage to an affected muscle. Connolly et al. report that the effectiveness of anti-oxidant therapy has been shown to be inconsistent among several studies examining it’s potential for treatment. Other nutritional supplements which have been investigated for treatment of DOMS include coenzyme–Q and L-carnitine, however neither supplement has been shown to effectively treat DOMS, and may even worsen symptoms.
Benefits of Warm-up
Unlike the use of NSAIDs and nutritional supplements, pre-exercise warm-up has been shown to be effective in reducing symptoms of DOMS. In his review, Szymanski (2001) notes that traditional warm-up before exercise has been suggested as a means of preparing the body for exercise, improving athletic performance, and reducing DOMS and associated muscle damage. Using a warm up to increase muscle temperature is thought to improve muscle function by leading to greater muscle elasticity, an increased resistance of muscle tissue to tearing, more relaxed muscles, an increased extensibility of connective tissues within muscle, and decreased muscle viscosity. This in turn allows for more efficient muscle contractions, which deliver increased speed and force. Szymanski also reports that several studies provide evidence of concentric warm-up before eccentric exercise, thus preparing the body for the stress caused by overloading the muscles with eccentric activity.
Szymanski (2001) adds that pre-exercise warm-up can be placed into two categories, general and specific. General warm-up is aimed at increasing core body temperature by performing movements that require the use of large muscle groups, such as calisthenics and running. Specific warm-up, mimicking the movement patterns of the actual exercises, is aimed at increasing the local muscle temperature in the muscles, which will be used in the specific sport or physical activity. Due to the benefits of warm-up it is advisable to precede an intense exercise bout with an adequate general and specific warm-up. Warm-up duration can vary greatly, depending of the intensity of physical activity, environmental conditions, and fitness level of clients (less fit people may need a longer warm-up).
In addition to warming up, Szymanski (2003) introduces the repeated-bout effect as a meaningful means of reducing DOMS. The repeated bout effect is a progressive adaptation to eccentric exercise. It has been reported that repeated bouts of lower intensity eccentric exercise performed 1-6 weeks before the initial higher intensity eccentric bouts have been shown to consistently reduce DOMS and exercise induced muscle damage. Thus, a gradual introduction of eccentric exercise, over a period of weeks, is encouraged. Szymanski states that the repeated bout effect is proposed to allow for a faster recovery of strength and range of motion in effected muscles, providing for increased resistance to damage after the first bout. It is also thought that muscle and connective tissue gradually adapt to increasing intensities of eccentric exercise, minimizing incidence and severity of DOMS.
With a better understanding of the causes of DOMS, the health and fitness professional is better equipped to help clients avoid it’s complications. It is hoped that the information in this article will add to the ‘tool box’ of knowledge from which personal trainers can draw from in an effort to optimize the health and fitness results obtained by their clients.