MARTINO, M., N. GLEDHILL, and V. JAMNIK. High &OV0312;O2maxwith no history of training is primarily due to high blood volume.Med. Sci. Sports Exerc., Vol. 34, No. 6, pp. 966–971, 2002.PurposeTo investigate the high &OV0312;O2maxobserved occasionally in young men who have no history of training.Methods&OV0312;O2max, blood volume (BV), maximal stroke volume (SVmax), maximal cardiac output (&OV0422;max), and related measurements (reported as mean ± SEM) were studied in six men (mean age 20.0 ± 0.5 yr) with no history of training, who all had a &OV0312;O2maxbelow 49 mL·kg−1·min−1(LO group) and six age- and weight-matched men (mean age 19.5 ± 0.5 yr) with no history of training, who all had a &OV0312;O2maxabove 62.5 mL·kg−1·min−1(HI group).ResultsCompared with the LO group, the HI group had a higher SVmax(149 ± 5 vs 102 ± 5 mL), higher &OV0422;max(28.9 ± 0.9 vs 20.0 ± 1.0 L·min−1) and higher BV (88.1 ± 3.8 vs 76.7 ± 0.9 mL·kg−1). The BV of four participants in the HI group (mean = 92.3 ± 4.3 mL·kg−1) was substantially higher than the BV of all participants in the LO group, but two participants in the HI group had a BV (mean = 79.7 ± 0.8 mL·kg−1) that was similar to the mean BV of the LO group.ConclusionThe primary explanation for the high &OV0312;O2maxobserved occasionally in young men who have no history of training is a naturally occurring (perhaps genetically determined) high BV that brings about a high SVmaxand &OV0422;max. However, some young men with no history of training have a high &OV0312;O2max, SVmax, and &OV0422;maxpossibly because a greater portion of their BV is hemodynamically active.