Beetroot juice is more beneficial than sodium nitrate for attenuating muscle pain after strenuous eccentric-bias exercise

The aim of this study was to compare the effects of beetroot juice (BTJ) and a nitrate only drink (sodium nitrate; SN) on indices of exercise-induced muscle damage (EIMD). Thirty recreationally active males consumed either BTJ (n = 10), a nitrate-matched SN drink (n = 10), or an isocaloric placebo (PLA; n = 10) immediately and at 24 and 48 h after performing 100 drop jumps. To assess muscle damage, maximal isometric voluntary contractions (MIVCs), countermovement jumps (CMJs), pressure-pain threshold (PPT), creatine kinase (CK), and high-sensitivity C-reactive protein (hs-CRP) were measured before, immediately after and at 24, 48, and 72 h following the drop jumps. BTJ and SN increased serum nitric oxide, which peaked at 2 h post-ingestion (136 +/- 78 and 189 +/- 79 mu mol.L-1, respectively). PPT decreased in all groups postexercise (P = 0.001), but was attenuated with BTJ compared with SN and PLA (P = 0.043). PPT was 104% +/- 26% of baseline values at 72 h after BTJ, 94% +/- 16% after SN, and 91% +/- 19% after PLA. MIVC and CMJ were reduced following exercise (-15% to 25%) and did not recover to baseline by 72 h in all groups; however, no group differences were observed (P > 0.05). Serum CK increased after exercise but no group differences were present (P > 0.05). hsCRP levels were unaltered by the exercise protocol (P > 0.05). These data suggest that BTJ supplementation is more effective than SN for attenuating muscle pain associated with EIMD, and that any analgesic effects are likely due to phytonutrients in BTJ other than nitrate, or interactions between them.