We tested the hypothesis that dietary nitrate-rich beetroot juice (BR) supplementation could partially offset deteriorations in O2 transport and utilization, and exercise tolerance, after blood donation. Twenty-two healthy volunteers performed moderate-intensity and ramp incremental cycle exercise tests prior to and following the withdrawal of ~450 mL of whole blood. Before donation, all subjects consumed 7 x 70 mL of nitrate-depleted beetroot juice shots (PL) in the 48 h preceding the exercise tests. During the 48 h after blood donation, subjects consumed 7 shots of either BR (each containing 6.2 mmol nitrate; n=11) or PL (n=11) before repeating the exercise tests. [Hemoglobin] and hematocrit were reduced by ~8-9% following blood donation (P<0.05), with no difference between the BR and PL groups. When compared with pre-donation, steady-state V̇O2 during moderate-intensity exercise was ~4% lower post-donation in BR (P<0.05) but was unchanged in PL. The ramp test peak power decreased from pre-donation (PL: 341 ± 70 vs. BR: 331 ± 68 W) to post-donation (PL: 324 ± 69 vs. BR: 322 ± 66 W) in both groups (P<0.05). However, the decrement in performance was significantly less in BR (2.7%) compared with PL (5.0%; P<0.05). Nitrate supplementation reduced the O2 cost of moderate-intensity exercise and attenuated the decline in ramp incremental exercise performance following blood donation. These results have implications for improving functional capacity following blood loss.
- O2 transport
- O2 uptake
- beetroot juice
- Copyright © 2016, American Journal of Physiology-Heart and Circulatory Physiology