The mechanism behind the anti-inflammatory effect of exercise is not fully understood. In some cases physical activity has proven almost/completely ineffective in reducing systemic inflammation. Thus, evaluating factors, which modify this response, is of particular significance. One of them may be related to iron metabolism. It is has been suggested that regular training reduces body iron stores, which can contribute to the anti-inflammatory response. Consequently, one of the anti-inflammatory effects of exercise can be related to changes in iron metabolism. Nevertheless, our preliminary data demonstrated that eight months of Nordic Walking training did not reduce body iron stores in approx. 25% of subjects, even if some of them were characterized by high blood ferritin (good indicator of body iron stores). This may be related to the effect of exercise on the concentration of hepcidin (main regulator of iron absorption, which acts as a negative regulator of iron efflux). It is well documented that a single bout of exercise induces an increase in blood hepcidin; however, data on the effect of regular training on the hepcidin concentration are limited.

Vitamin D is another factor, which could influence the anti-inflammatory effect of exercise. It has been suggested that individuals involved in physical activity have higher concentrations of 25OHD (indicator of vitamin D status). Vitamin D inhibits the expression of pro-inflammatory cytokines, which is considered the main mechanism of its anti-inflammatory action. It is worth noting that population in Poland is characterized by low status of vitamin D. Thus, it is possible that the anti-inflammatory effect of exercise will be modified by the vitamin status. Moreover, vitamin D has been shown to protect against muscle atrophy both in elderly and younger people. Its concentration has been correlated with muscle strength.

Inflammation has been observed to be associated with an increase of the autophagy-inducing stress protein, HMGB1, which mediates muscle atrophy. Measurement of plasma amino acid profile will be helpful to assess the impact of exercise on muscle proteolysis. Moreover, the link between exercise, vitamin D status and HMGB1 has not yet been established. In addition, a range of interactions induced by exercise involves the release of the newly discovered protein, irisin, form the muscle and its improving effect on the cognitive function through the synthesis of brain-derived neurotrophic factor (BDNF). Data on the effect of regular training on irisin concentration in elderly people is lacking.

Overall, our research interest focuses on the role of the factors mediating the anti-inflammatory effect of exercise and the way they stimulate or inhibit adaptive changes. The proposed project draws on our long experience in investigating the effects of exercise on iron metabolism as well as other physical methods supporting the anti-inflammatory action of physical activity. Latest published papers indicate that the concentration of vitamin D, also in training adaptation, can modulate immunological response to exercise. Therefore, verifying our hypothesis would also allow us to determine if the concentration of vitamin D can limit adaptation to physical activity.