Immunologic mediators as parameters of the reaction to strenuous exercise

Delayed muscle soreness. The inflammatory response to muscle injury and its clinical implications

Delayed onset muscle soreness (DOMS) is a sensation of discomfort that occurs 1 to 2 days after exercise. The soreness has been reported to be most evident at the muscle/tendon junction initially, and then spreading throughout the muscle. The muscle activity which causes the most soreness and injury to the muscle is eccentric activity. The injury to the muscle has been well described but the mechanism underlying the injury is not fully understood. Some recent studies have focused on the role of the cytoskeleton and its contribution to the sarcomere injury. Although little has been confirmed regarding the mechanisms involved in the production of delayed muscle soreness, it has been suggested that the soreness may occur as a result of mechanical factors or it may be biochemical in nature. To date, there appears to be no relationship between the development of soreness and the loss of muscle strength, in that the timing of the two events is different. Loss of muscle force has been observed immediately after the exercise. However, by collecting data at more frequent intervals a second loss of force has been reported in mice 1 to 3 days post-exercise. Future studies with humans may find this second loss of force to be related to DOMS. The role of inflammation during exercise-induced muscle injury has not been clearly defined. It is possible that the inflammatory response may be responsible for initiating, amplifying, and/or resolving skeletal muscle injury. Evidence from the literature of the involvement of cytokines, complement, neutrophils, monocytes and macrophages in the acute phase response are presented in this review. Clinically, DOMS is a common but self-limiting condition that usually requires no treatment. Most exercise enthusiasts are familiar with its symptoms. However, where a muscle has been immobilised or debilitated, it is not known how that muscle will respond to exercise, especially eccentric activity.

How physical exercise influences the establishment of infections

During exercise, leucocytes are recruited to the blood, and if muscle damage occurs the cytokine level is enhanced. After prolonged, intense exercise the number of lymphocytes in the blood is reduced, and the function of natural killer cells is suppressed; furthermore, secretory immunity is impaired. During this time of immunodepression, often referred to as 'the open window', the host may be more susceptible to micro-organisms bypassing the first line of defence. This is of interest to top athletes who perform frequent severe exercise. Clinical observations regarding an increased risk of infections in top athletes are compatible with this model. However, in those performing regular moderate exercise the immune system will often be temporarily enhanced and this will protect these individuals from infections.

Leucocytosis as a marker of organ damage induced by chronic strenuous physical exercise

The effects of strenuous physical exercise on the serial changes in the haematological, biochemical and hormonal markers were investigated. A group of 14 soldiers, aged 24-36 years, took part in a military training course for about 13 weeks. After severe exercise stress, an increase (90%) in the number of peripheral blood leucocytes was observed. The degree of leucocytosis showed a close correlation with the values of some serum parameters, such as concentrations of aspartate aminotransferase (AST; r = 0.747), lactate dehydrogenase (LD; r = 0.748), blood urea nitrogen (r = 0.756), creatine kinase (CK; r = 0.637), manganese-superoxide dismutase (Mn-SOD; r = 0.508), alanine aminotransferase (ALT; r = 0.542) and uric acid (r = 0.538), and concentrations of urinary parameters, such as vanilmandelic acid (r = 0.429) and free cortisol (r = 0.437). The subjects showing prominent leucocytosis over 9500 cells.microliters-1 exhibited a lower concentration of serum cholinesterase than those who showed milder leucocytosis. The serum Mn-SOD concentration was closely correlated with the serial changes in serum concentrations of AST, ALT, LD and CK, indicating exercise-induced muscle and liver damage. The change in peripheral leucocyte number was assumed to be diagnostically informative and may be a prognostic marker, reflecting organ damage and restoration after strenuous physical exercise.

An in vitro investigation into the effects of repetitive motion and nonsteroidal antiinflammatory medication on human tendon fibroblasts

Soft tissue injuries due to repetitive motion are common sports injuries and are often treated with antiinflammatory therapies. We investigated the in vitro effects of repetitive motion and nonsteroidal antiinflammatory medication on human tendon fibroblasts. In addition, we studied the effects related to the presence of inflammatory cells. Repetitive motion was associated with an increased release of prostaglandin E2 and increased deoxyribonucleic acid (DNA) and protein synthesis. The presence of nonsteroidal antiinflammatory medication decreased prostaglandin E2 release and DNA synthesis but increased protein synthesis. Contact with macrophages caused a marked additional increase in prostaglandin E2 and a concomitant increase in DNA synthesis. Release of interleukin-6 by the macrophages also suggested that this cytokine plays a role in the response to repetitive motion. Our results can aid in the search for a more scientific approach to the treatment of soft tissue injuries associated with repetitive motion. They suggest that nonsteroidal antiinflammatory medication may have potentially negative effects during the proliferative phase of a healing since it was associated with decreased DNA synthesis. However, it may be beneficial in the maturation and remodeling phase since it stimulated protein synthesis.

Effects of high volume and/or intense exercise on selected blood chemistry parameters

The goal of athletic training is to provide the body with a stimulus to adapt, increasing the capacity of the various systems to perform increased work loads. However, the magnitude of the stress must be large enough to induce the synthesis of new enzymes, tissues, and yet not so large that the biochemical and physiological processes of recovery are depressed. As each individual undergoes this process at a different rate, objective evaluation of the level of fatigue and adaptation is of enormous value in directing the training program of an athlete. The role of iron in the body is such that this element can be used as a marker of both adaptation to training and as an indicator of an acute inflammatory response to exercise. The various clinical measurements of iron in transport, storage, and in hematological parameters are discussed in this paper, relative to athletic populations. In addition expected changes in the level of the acute inflammatory protein, alpha 1-antitrypsin are also discussed relative to acute and chronic training protocols. Data is presented indicating that measurement of serum iron, transferrin, serum ferritin, and alpha 1-antitrypsin can be used to differentiate between an inflammatory response to tissue damage and infection. These parameters can also provide information as to the state of recovery, or lack thereof, experienced by an athlete to both acute and chronic training programs. The use of biochemical markers can help to avoid an overstress situation.

Are similar inflammatory factors involved in strenuous exercise and sepsis?

An increasing body of data suggest that strenuous exercise triggers an inflammatory response having some similarity with those occurring in sepsis. Indices of this inflammatory response to exercise (IRE) especially include leukocytosis, release of inflammatory mediators and acute phase reactants, tissue damage, priming of various white blood cell lines, production of free radicals; activation of complement, coagulation and fibrinolytic cascades. Inflammatory responses to strenuous exercise and sepsis could in part be due to the release of endotoxin in blood as common triggering factor, but it seems that tissue damage and/or contact system activation are more important triggering mechanisms in exercising subjects. While the magnitude and duration of cellular and humoral changes associated with IRE are quite different from those observed in sepsis, recent human studies suggested that chronic and/or excessive IRE could have adverse effects. Among the possible consequences of acute and chronic IRE are delayed onset muscular soreness and loss of force, cardiovascular complications, intravascular hemolysis, hypoferraemia and increased susceptibility to infection.

Exercise and the immune system: a model of the stress response?

Exercise influences natural immunity, T- and B-cell functions, and cytokine responses, through circulatory (hemodynamic) changes and by endocrine hormones secreted in response to physical stress. The magnitude of the effects on the immune system reflects the intensity, duration and chronicity of the exercise. In this review, Laurie Hoffman-Goetz and Bente Klarlund Pedersen suggest that exercise-immune interactions can be viewed as a subset of stress immunology.