Abstract
It is known that intensive physical activity alters the immune system’s functionality. However, the influence of the intensity and duration of exercise needs to be studied in more depth. We aimed to establish the changes in the innate immune response induced by two programmes of intensive training in rats compared to sedentary rats. A short training programme included 2 weeks of intensive training, ending with an exhaustion test (short training with exhaustion, S-TE). A second training programme comprised 5-week training including two exhaustion tests and three trainings per week. In this case, immune status was assessed before (T), immediately after (TE) and 24 h after (TE24) an additional final exhaustion test. Biomarkers such as phagocytic activity, macrophage cytokine and reactive oxygen species (ROS) production, and natural killer (NK) cell activity were quantified. S-TE was not enough to induce changes in the assessed innate immunity biomarkers. However, the second training was accompanied by a decrease in the phagocytic activity, changes in the pattern of cytokine secretion and ROS production by macrophages and reduced NK cell proportion but increased NK cytotoxic activity. In conclusion, a 5-week intense training programme, but not a shorter training, induced alterations in the innate immune system functionality.
Highlights
It is known that intensive physical activity alters the immune system’s functionality
The first training programme included male and female rats (S-TE groups), which were intensively trained for 2 weeks and afterwards, they carried out a final exhaustion test (Fig. 1)
In the additional final exhaustion test, these animals ran a maximum distance of 1419.29 ± 100.03 m, which was lower than that run by female runner rats of the short intensive training with exhaustion (S-TE) group (p < 0.05) in the first training programme
Summary
It is known that intensive physical activity alters the immune system’s functionality. Immune status was assessed before (T), immediately after (TE) and 24 h after (TE24) an additional final exhaustion test Biomarkers such as phagocytic activity, macrophage cytokine and reactive oxygen species (ROS) production, and natural killer (NK) cell activity were quantified. The second training was accompanied by a decrease in the phagocytic activity, changes in the pattern of cytokine secretion and ROS production by macrophages and reduced NK cell proportion but increased NK cytotoxic activity. The observations regarding the amount and intensity of exercise and risk of illnesses have led to the hypothesis that their relationship fits a J-shaped curve[11] This means that very low physical activity or no training is associated with a higher risk of illness compared to moderate activity or training load, whereas very high training loads are related to a higher risk of illness[10]. Controversial results have been described by Bigley et al.[29] who observed an increase in NK cell cytotoxicity in trained humans, whereas Campbell et al.[30] showed no differences in NK cell cytotoxic activity in post-menopausal women after 12 months of exercise
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