Sport-Specific Physiological Adaptations in Highly Trained Endurance Athletes

Purpose: This study aims to compare maximal oxygen uptake (VO2max), blood volume (BV), hemoglobin mass (Hb(mass)), and brachial endothelial function, measured as flow-mediated dilatation (FMD), in international-level endurance athletes primarily exercising with the whole body (cross-country skiing), lower body (orienteering), or upper body (flatwater kayak). Methods: Seventeen cross-country skiers, 15 orienteers, and 11 flatwater kayakers were tested for VO2max, BV, Hb(mass), and FMD. Additionally, body composition and annual training (type, volume, and intensity of training) were analyzed. Results: Absolute and body-mass-normalized VO2max values were 11.3% and 9.9% higher, respectively, in skiers (5.83 0.60 Lmin(-1) and 77.9 +/- 4.2 mLmin(-1)kg(-1)) compared to orienteers (5.24 +/- 0.45 Lmin(-1) and 70.9 +/- 3.5 mLmin(-1)kg(-1)) (P < 0.01), whereas kayakers (5.78 +/- 0.56 Lmin(-1) and 73.7 +/- 6.3 mLmin(-1)kg(-1)) did not differ from skiers. BV was 9.9%-11.8% higher in skiers and orienteers compared to kayakers when normalized for total body mass and fat-free mass, and skiers had 9.2% and 9.9% higher Hb(mass) normalized for total body mass and fat-free mass compared to kayakers (all P < 0.05). Arterial diameter was 11.8%-15.0% larger in kayakers (4.38 +/- 0.63 mm) and skiers (4.22 +/- 0.36 mm) compared to orienteers (3.81 +/- 0.32 mm) (P < 0.05), whereas FMD did not differ between groups. Conclusions: This study indicates that higher VO2max in cross-country skiers and greater arterial diameters in the arms of skiers and kayakers are sport-specific physiological adaptations to chronic endurance training in whole-body and upper-body exercise modes. However, variations in these variables are not associated with BV or Hb(mass).