Nicolas Bourdillon

Purpose : Total hemoglobin mass (tHb mass ) and blood volume (BV) are important determinants of maximal oxygen uptake and endurance capacity. Higher-caliber endurance athletes usually possess higher tHb mass and BV values. This study aimed to compare tHb mass and BV among swimmers of diverse competitive calibers and distances. Methods : Thirty swimmers (16 female and 14 male) participated in the study: 3 were tier 5, world class (869 [59] FINA points); 15 were tier 4, elite/international (853 [38] points); and 12 were tier 3, highly trained/national (808 [35] points). They specialized in competition distances ranging from 200 m to open-water 10 km. Between February 2019 and February 2020, all swimmers had their tHb mass and BV measured by carbon monoxide rebreathing 1 to 6 times and participated in multiple competitions and race events. Results : Relative tHb mass and BV were not different ( P > .05) between tiers among women or among men (pooled tHb mass values 14.5 [0.5], 12.5 [1.5], 12.6 [2.3] g/kg for tier 5, tier 4, and tier 3, respectively). No differences were observed in relative tHb mass ( P = .215) and BV ( P = .458) between pool and open-water swimmers or between 200-, 400-, and 1500-m specialists ( P > .05). No significant correlations were found between the highest measured absolute or relative tHb mass and BV and the highest FINA points scored over the follow-up period ( R = −.42–.17, P = .256–.833), irrespective of competition distance. Conclusion : tHb mass and BV values did not differ between swimmers of different calibers or among competition distances. Furthermore, these values did not correlate with FINA points, either in males or in females. The present results indicate that hematological characteristics may have a lesser impact on swimming performance than on land-based endurance sports.