Exercise-induced muscle damage (second phase)

In the second phase of exercise-induced muscle damage, an inflammatory process takes place in which certain genetic variants may contribute to more or less muscle damage.

Certain gene variations, or polymorphisms, have been associated with exercise-induced muscle damage, i.e., individuals with certain genotypes experience greater muscle damage and require longer recovery after strenuous exercise.

In the initial phase of muscle damage, mechanical damage occurs. The second phase is a consequence of the first and consists of an inflammatory response. The products originating from the damaged muscle tissue attract immune cells (a process known as chemotaxis) which will initiate the inflammatory process. In addition, the release of certain molecules, known as cytokines (mainly IL1B, IL6 and TNF) that enhance the inflammatory process occurs.

Variants in the genes coding for these cytokines appear to be involved in the development of this second inflammatory phase of muscle damage.

The fact that a greater amount of muscle damage occurs due to the second phase of exercise depends on the intensity of the inflammatory response carried out by the immune system. Three markers associated with the production of inflammatory activity compounds produced by the immune system and located in the TNF, IL1B and IL6 genes have been identified.

One of the genes found is the TNF gene, responsible for the production of tumor necrosis factor, an inflammatory activity factor associated with insulin levels and predisposition to metabolic disorders, as well as activation of muscle protein degradation (via proteasome). This is why this factor is important in the processes of injury and remodeling of muscle tissue.

The other two markers are found in the IL1B gene, which produces interleukin 1B, whose expression in muscle fibers is elevated a few days after physical exercise, also inducing the expression of other proinflammatory genes; and in the IL6 gene, which produces interleukin 6, with proinflammatory activity. It has been observed that, after eccentric exercise, muscle can induce local expression of the cytokine IL-6.

Number of observed variants

13.5 million variants

Number of variants analyzed in the study

3 variants

Bibliography

Baumert P, Lake MJ, Stewart CE, Drust B, Erskine RM. Genetic variation and exercise-induced muscle damage: implications for athletic performance, injury and ageing. Eur J Appl Physiol, 2016; 116(9):1595–625.

Pereira DS, Mateo ECC, de Queiroz BZ, Assumpção AM, Miranda AS, Felício DC, et al. TNF-?, IL6, and IL10 polymorphisms and the effect of physical exercise on inflammatory parameters and physical performance in elderly women. Age (Omaha), 2013; 35(6):2455–63.

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