Abstract
PurposeIt remains unknown how different training intensities and volumes chronically impact circulating lymphocytes and cellular adhesion molecules. First, we aimed to monitor changes in NK and T cells over a training season and relate these to training load. Second, we analyzed effects of training differences between swimmers on these cells. Finally, we examined if changes in lymphocytes were associated with sICAM-1 concentrations.MethodsWe analyzed weekly training volume, training intensity, proportions of T and NK cells and serum sICAM-1 in eight sprint (SS) and seven middle-distance swimmers (MID) at three points over a 16-week training period: at the start (t0), after 7 weeks of increased training load (t7) and after 16 weeks, including 5-day taper (t16).ResultsTraining volume of all swimmers was statistically higher and training intensity lower from t0–t7 compared to t7–t16 (p = 0.001). Secondly, training intensity was statistically higher in SS from t0–t7 (p = 0.004) and t7–t16 (p = 0.015), while MID had a statistically higher training volume from t7–t16 (p = 0.04). From t0–t7, NK (p = 0.06) and CD45RA+CD45RO+CD4+ cells (p < 0.001) statistically decreased, while CD45RA−CD45RO+CD4+ cells (p = 0.024) statistically increased. In a subgroup analysis, SS showed statistically larger increases in NK cells from t7–t16 than MID (p = 0.012). Lastly, sICAM-1 concentrations were associated with changes in CD45RA−CDRO+CD4+ cells (r = − 0.656, p = 0.08).ConclusionThese results indicate that intensified training in swimmers resulted in transient changes in T and NK cells. Further, NK cells are sensitive to high training volumes. Lastly, sICAM-1 concentrations may be associated with the migration and maturation of CD4+ cells in athletes.
Highlights
Bouts of intensive exercise and strenuous periods of training have previously been shown to lead to changes in the populations of circulating lymphocytes in the bloodstream, while periods with reduced training load may reverse some of these changes (Cosgrove et al 2012; Gleeson et al 1995; Mujika et al 1996; Rama et al 2013; Teixeira et al 2014)
Proportions of natural killer (NK) cells statistically decreased from t0 to t7 (p = 0.006, effect size r (ES) = 0.52) and statistically increased from t7 to t16 (p = 0.006, ES = 0.53)
Changes in soluble ICAM-1 (sICAM-1) were associated with changes in proportions of memory CD4+ (CD45RA− CD45RO+ CD4+) cells from t7 to t16 (r = − 0.589, p = 0.002) and over the entire training period (r = − 0.656, p = 0.008, Fig. 3)
Summary
Bouts of intensive exercise and strenuous periods of training have previously been shown to lead to changes in the populations of circulating lymphocytes in the bloodstream, while periods with reduced training load may reverse some of these changes (Cosgrove et al 2012; Gleeson et al 1995; Mujika et al 1996; Rama et al 2013; Teixeira et al 2014). Previous training studies have consistently shown a decrease in numbers of natural killer (NK) cells as a result of long periods of training (> 12 weeks) (Gleeson et al 1995, 2000; Rama et al 2013). Numbers of Treg cells were shown to statistically increase after 1 week of highintensity training in adult hockey players (Weinhold et al 2016). The distribution and function of different subclasses of lymphocytes are essentially altered in response to exercise
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