Immune System Response to Changes in Training Intensity and Volume in Runners

Abstract

This study 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-day phases over a 40 day training period. Phase 1 and phase 3 were "baseline" phases of low volume/low intensity running (LV/LI). Phase 2 and phase 4 consisted of either high volume/low intensity (HV/LI) or high volume/high intensity (HV/HI) training. Subjects were randomly assigned to one of 2 different crossover training group orders: 1) LV/LI, HV/LI, LV/LI, HV/HI or 2) LV/LI, HV/HI, LV/LI, HV/LI. HV/LI training involved doubling the LV distance run at the same LI of 60-70% V02 max. The HV/HI phase consisted of the same volume as the HV/LI phase, but alternate days were replaced with a series of high intensity 1000 m intervals (95-100% V02 max). Venous blood samples were drawn at rest on days 1, 4 and 7 and 5 minutes post-exercise on days 1 and 7 of each 10-day phase. Lymphocyte subsets were determined by flow cytometry using monoclonal antibodies for total T (CD3+), T-helper (CD4+), T-suppressor (CDS+) lymphocytes and HLA-DR+ (a B cell and "activated" T-lymphoid cell marker). IgA, IgG and IgM levels were obtained by ELISA analysis. This study revealed remarkable stability of humoral (antibody) immune components during and after runs of various intensities and volumes. Immunoglobulin levels were not significantly affected by alterations in volume or intensity over the 4 training phases. A transient decrease was observed in the T-lymphocyte percentages of CD3+, CD4+ and the CD4/CD8 ratio 5 minutes post-exercise which was significant (p <.05) during the HV/LI and HV/HI phases. Adaptation of lymphocyte subpopulations occurred with repeated exposure to increases in volume and intensity. A training order effect was suggested whereby an initial HI phase, was more immunosuppressive and possibly negated the effects of subsequent HV phases. Results indicate that the exercise-induced lymphocyte subset reduction is transient and suggest that the extent of the reduction is more dependent upon training intensity than volume, and the order of exposure to the high-intensity stimulus may determine the magnitude of subsequent responses.