Immune responses to training: how critical is training volume?

Background, Lf the volume of training undertaken is sufficient to induce a negative energy balance, the anticipated benefit of an enhanced immune resp onse may be reduced or lost. Methods. 33 sedentary but healthy male volunteers aged 19-29 years, recruit ed from the university community. A peak oxygen intake measurement (cycle e rgometer) and a 60-min exercise challenge at 60% of aerobic power were perf ormed before and after 12 wk of treatment, Total leukocytes, subsets, CD3(), CD4(+) CD8(+), CD16(+), CD19(+), and CD25(+) counts (FACScan), cytolytic activity (Cr-51 release) and cell proliferation (PHA and PWM) were measure d, with subjects assigned arbitrarily to one of three groups: light trainin g (18 subjects, aerobic exercise at 70-85 % HRmax 3 times/wk), moderate tra ining (9 subjects, similar programme 4-5 times/wk) and control (6 subjects) . Results, Groups were initially well-matched in physical and physiological t erms. Training increased aerobic power (8%, light, 21% moderate training), with a loss of body mass and fat in the moderate training group. Controls s howed no changes. Resting CD16+ counts increased by 27% (light training) an d CD16(+) CD56(+) counts by 21% (moderate training), with less post-exercis e suppression of counts than at recruitment. Light training also decreased CD3+ and CD4+ counts without changing the CD4(+)/CD8(+) ratio. Moderate tra ining decreased resting CD19(+) count, Conclusions. From the viewpoint of immune function, the optimal training re gimen is of low volume. Moderate training sufficient to induce a negative e nergy balance yields a smaller increase in numbers of non-MHC-restricted cy totoxic cells, and carries the negative consequence of diminished B cell co unts.