Figure 1.

Acute and chronic effects of moderate and vigorous exercise. Depending on the increase in heart rate (pink area), exercise can be classified as moderate exercise or vigorous exercise. The effects of exercise can be classified as acute (light blue area) or chronic (blue area). Acute moderate exercise induces a leukocytosis in the blood (a) and a transient upregulation of the intracellular vitamin D receptor (VDR) in T lymphocytes, inducing T cell phenotype switching (b). Further, moderate exercise enhances the expression of CD11b on neutrophils acutely and chronically (c). In the long term, physical exercise improves the trafficking behavior of both CD8+ cells and natural killer (NK) cells by regulating the expression of CXCR3 (d). Vigorous exercise induces alterations in lymphocyte numbers in a biphasic way: an instantaneous lymphocytosis is followed by transient lymphopenia (e). Further, non-classical monocytes are increased during exercise (f). Vigorous exercise acutely elevates the expression of CD39 and CD73 on CD4+ T lymphocytes which assist in the conversion of adenosine triphosphate (ATP)/adenosine diphosphate (ADP) into adenosine monophosphate (AMP)/adenosine, respectively (g). Vigorous exercise reduces the expression of Toll-like receptors (TLRs) 1, 2, and 4 on CD14+ monocytes in the early post-exercise period, inducing anti-inflammatory effects (h). In the long term, exercise also promotes anti-inflammatory effects by encouraging anti-inflammatory phenotype switching in lymphocytes and monocytes. The balance between T_H1 and T_H2 cells shifts in favor of T_H2 (i) and the frequency of intermediate and non-classical monocytes decreases due to diminished expression of CD16 (j). Finally, both moderate and vigorous exercise preserve thymic output (k).