Eight weeks of heavy strength training increases hemoglobin mass and Vo_2peak in well-trained to elite female and male rowers

O-2-transport and endurance exercise performance are greatly influenced by hemoglobin mass (Hb(mass)), which largely depends on lean body mass (LBM). This study investigated the effects of 8 wk with three weekly sessions of conventional (3-SET: 3 x 10 reps) or high-volume strength training (10-SET: 5-10 x 10 reps) on LBM, Hb(mass), muscle strength, and exercise performance in female and male rowers. Hematological parameters were obtained through CO rebreathing and body composition by dual-energy X-ray absorptiometry (DEXA) scans before and after the training period. Concomitantly, Vo(2peak) was determined during 2-km ergometer rowing and muscle strength by isometric midthigh pull. There were no differences in training responses between groups for any of the parameters. Pooled data revealed overall increments for Hb(mass) (10-SET: 882 +/- 199 g to 897 +/- 213 g; 3-SET: 936 +/- 245 g to 962 +/- 247 g, P = 0.02) and Vo(2peak) (10-SET: 4.3 +/- 1.0 to 4.4 +/- 0.9 Lmin(-1); 3-SET: 4.5 +/- 0.9 to 4.6 +/- 0.9 Lmin(-1), P = 0.03), whereas LBM remained unchanged (10-SET: 58.7 +/- 10.5 to 58.7 +/- 10.1 kg; 3-SET: 64.1 +/- 10.8 to 64.5 +/- 10.6 kg, P = 0.42). Maximal isometric midthigh pull strength increased (10-SET: 224 +/- 47 kg to 237 +/- 55 kg; 3-SET: 256 +/- 77 kg to 281 +/- 83 kg, P = 0.001). Strong associations were observed between LBM and Hb(mass) and Vo(2peak) (r(2) = 0.88-0.90), entailing sex differences in Hb(mass) and Vo(2peak). Normalizing Vo(2peak) to LBM reduced the sex difference to similar to 10%, aligning with the sex difference in Hb(mass)LBM-1. Strength training successfully increased Hb(mass) and Vo(2peak) in elite female and male rowers, without an additional effect from increased training volume. Moreover, sex differences in Vo(2peak) were mainly explained by differences in LBM, but likely also by differences in Hb(mass)LBM-1