Immune response to changes in training intensity and volume in runners.

We examined the acute and chronic effects of changes in training volume and intensity on the blood lymphocyte percentages and immunoglobulin levels in runners. Twelve runners participated in four 10-d phases of low volume/low intensity (LV/LI), high volume/low intensity (HV/LI), or high volume/high intensity (HV/HI) running. Subjects were assigned to one of two different training group orders: 1) LV/LI, HV/LI, LV/LI, HV/HI; or 2) LV/LI, HV/HI, LV/LI, HV/LI. Venous blood was drawn at rest on days 1, 4, and 7; and 5 min post-exercise on days 1 and 7 of each 10-d phase. Lymphocyte subsets were determined by flow cytometry for CD3+, CD4+, CD8+, and HLA-DR+. IgG, and IgM levels were obtained by ELISA analysis. Immunoglobulin, CD8+ and HLA-DR+ levels, and pre-exercise plasma cortisol concentrations were not significantly affected by alterations in volume or intensity. A transient decrease (P < 0.05) was observed in CD4+ and the CD4/CD8 ratio 5 min post-exercise during the HV/LI and HV/HI phases. Results indicate that the exercise-induced lymphocyte subset reduction is transient and suggest that it is more dependent upon training intensity than volume, and the training order of exposure to the high-intensity stimulus may determine the magnitude of subsequent responses.