Purpose: To investigate the T-lymphocyte response to a period of increased training volume in trained females compared to habitual activity in female controls. Methods: Thirteen trained female (19.8 ± 1.9 yrs) soccer players were monitored during a two-week long high volume training period (increased by 39%) and thirteen female untrained (20.5 ± 2.2 yrs) controls were monitored during two-weeks of habitual activity. Blood lymphocytes, collected at rest, were isolated before and after the two-week period. Isolated lymphocytes were assessed for the cell surface expression of the co-receptor CD28, a marker of T-lymphocyte naivety, and CD57 a marker used to identify highly-differentiated T-lymphocytes. Co-expression of these markers was identified on helper CD4+ and cytotoxic CD8+ T-lymphocytes. In addition a further population of ?d+ T-lymphocytes were identified. Plasma was used to determine Cytomegalovirus (CMV) serostatus. Results: No difference was observed in the T-lymphocyte populations following the two-week period of increased volume training. At baseline the number of total CD3+, cytotoxic CD8+, naïve (CD8+ CD28+ CD57-), intermediate (CD8+ CD28+ CD57+) T-lymphocytes and the number and proportion of ?d+ T-lymphocytes were greater in the trained compared to the untrained females (p < 0.05). The proportion of CD4+ T-lymphocytes was greater in the untrained compared to the trained (p < 0.05), in turn the CD4+:CD8+ ratio was also greater in the untrained females (p < 0.05). Inclusion of percentage body fat as a covariate removed the main effect of training status in all T-lymphocyte sub-populations, with the exception of the ?d+ T-lymphocyte population. 8% of the untrained group was defined as positive for CMV whereas 23% of the trained group was positive for CMV. However, CMV was not a significant covariate in the analysis of T-lymphocyte proportions. Conclusion: The period of high volume training had no effect on T-lymphocyte populations in trained females. However, baseline training status differences were evident between groups. This indicates that long-term exercise training, as opposed to short-term changes in exercise volume, appears to elicit discernible changes in the composition of the blood T-lymphocyte pool.
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