Body composition, maximal aerobic performance and inflammatory biomarkers in endurance-trained athletes Jaak J€ urim€ ae 1 , Vallo Tillmann 2 , Priit Purge 1 and Toivo J€ urim€ ae 1 1 Institute of Sport Pedagogy and Coaching Sciences, Centre of Behavioral, Social and Health Sciences, University of Tartu, and 2 Department of Paediatrics, Children’s Clinic of Tartu University Hospital, University of Tartu, Tartu, Estonia Summary Correspondence Jaak J € urim€ ae, Institute of Sport Pedagogy and Coaching Sciences, University of Tartu, 18. € Ulikooli St., 50090 Tartu, Estonia E-mail: jaak.jurimae@ut.ee Accepted for publication Received 5 May 2015; accepted 3 August 2015 Key words body composition; inflammatory profile; maximal aerobic performance; rowers This study was designed to examine the relationships between body composition, cardiorespiratory fitness and simultaneously measured inflammatory parameters in endurance-trained athletes. In 20 well-trained rowers (190  29 years; 1856  48 cm; 857  108 kg; 171  51% body fat; maximal oxygen con- sumption [VO 2 max]: 639  85 ml min 1 kg 1 ), body composition was mea- sured by dual-energy X-ray absorptiometry and cardiorespiratory fitness by direct VO 2 max test. Twelve inflammatory factors [interleukin (IL)-2, IL-4, IL-6, IL-8, IL-10, vascular endothelial growth factor, interferon-gamma (IFN-c), tumour necrosis factor-alpha, IL-1a, IL-1b, monocyte chemoattractant protein-1 (MCP-1), epidermal growth factor (EGF)] were analysed from serum samples. Serum IFN-c was related (P<005) to fat-free mass (FFM) (r = 056) and muscle mass (r = 050). The stepwise regression analysis showed that IFN-c explained 275%, and IFN-c and IL-6 together explained 398% of the variability of FFM, while IFN-c explained 211%, and IFN-c together with EGF explained 366% of the variability of muscle mass in male rowers. Serum IL-8 (r = 065) and VEGF (r = 048) correlated (P<005) with VO 2 max kg 1 . Serum IL-8 explained 385% of the variability of VO 2 max kg 1 . Significant correlations were also found among several inflammatory parameters, indicating that various inflammatory cytokines act on the body as an ensemble. In conclusion, this cross-sectional study in endurance-trained male rowers showed that FFM and muscle mass were nega- tively correlated with serum IFN-c level, whereas cardiorespiratory fitness was negatively related to serum IL-8 level. Introduction Inflammatory cytokines are intercellular signalling molecules that help to control and mediate interactions among different cells involved in inflammation and immune responses (Nieman et al., 2001; Beavers et al., 2010). There are several reports to indicate that resting serum levels of various inflammatory cytokines are higher in obese than in normal-weight children (Utsal et al., 2012) and adults (Shanely et al., 2013). It is also well known that obesity and aging are both associated with increased risk for atherosclerosis and cardiovascular diseases (Baker et al., 2007; Zoico et al., 2010), where low-grade inflammation has been shown to be a risk factor for the pro- gression of cardiovascular diseases (Beavers et al., 2010). We have shown before that many mediators of low-grade inflam- mation such as interleukin (IL)-6, IL-8, interferon-gamma (IFN-c), monocyte chemoattractant protein-1 (MCP-1) and high-sensitive C-reactive protein (hsCRP) are involved in the development of childhood obesity (Utsal et al., 2012), and higher serum pro-inflammatory cytokine IL-6 has been corre- lated with lower cardiorespiratory fitness in obese children (Utsal et al., 2013). Higher cardiorespiratory fitness has been found to be associated with lower risk of cardiovascular dis- eases (Rodrigues et al., 2007). Negative correlations between different biochemical markers of inflammation and body com- position and/or physical fitness status have been reported in people of sedentary lifestyle (Beavers et al., 2010). However, similar data in physically fit and lean population are quite lim- ited (Nieman et al., 2012; Shanely et al., 2013). Shanely et al. (2013) found that low body mass index (BMI) together with high aerobic physical fitness was strongly associated with low levels of inflammatory markers, such as hsCRP, IL-6, tumour necrosis factor-alpha (TNF-a) and granulocyte colony-stimulat- ing factor, but not to MCP-1 and IL-10 levels. Lean and highly fit endurance athletes have usually in well-rested state relatively low levels of inflammatory markers, whereas in overreached Clin Physiol Funct Imaging (2015) doi: 10.1111/cpf.12299 1 © 2015 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd