Biomechanics and Medicine in Swimming XI

more cytotoxic capacity, and NK bright ( 10%) with a higher affinity to
IL-2 and a large capacity to produce cytokines: IFN-γ, TNF-β, GM-
CSF, IL-10, IL-13 after monokine stimulation (Cooper et al. 2001). The
striking sensivity of NK cells to exercise stress provides strong support
that these cells may be implicated as a potential link between regular
physical activity and overall health status (Timmons & Cieslaak, 2008).
However the results are not without some controversy, as a large
number of studies are conducted using in-vitro assays, and when peripheral
blood samples were used, it was not possible to determine the true
nature of the alterations observed in the immune parameters: whether
it is a decrease in immune function or an adaptive mechanism such as
changes in the cells redistribution patterns.
The aim of this study was to analyze the variation of hormonal and
immunological parameters and the incidence of URTIS, during the first
7 weeks of a winter training season in a group of national level Portuguese
male swimmers.
Methods
This study sample consisted of 13 male swimmers of Portuguese national
level (17.2± 1.3 years old, 174.9 ±5.8 cm, 65.8±6.8 kg of height and
weight respectively). All subjects gave their written informed consent.
Training volume and intensity were controlled as well as the time
spent in dry land activities. Blood samples were collected: 1) in the beginning
of the winter season, after an off training period of 6 weeks (t0),
2) after 7 weeks of training (t1), by venopuncture, always at the same
time of the day (between 15 and 17h. At (t1) a time lapse of 48 hours of
rest after the last training session was respected.
Total leukocyte counts and percentage were measured on a Coulter
counter diff TM Analyser. The lymphocyte populations and subsets
(CD3+, CD4+, CD8+, CD19+ and CD56+) were accessed by flow cytometry
(FACSCalibur; BD, San Jose, C.A., USA).
The serum concentration of cortisol and free testosterone were determined
by electrochemiluminescence (Immulite 2000) at the same time
points. The URTIS were assessed by self-report in daily log books. Statistical
analysis using the non-parametric Wilcoxon test was conducted
(p