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