Minimal muscle damage after a marathon and no influence of beetroot juice on inflammation and recovery

This study examined whether beetroot juice (BTJ) would attenuate inflammation and muscle
damage following a marathon. Using a double blind, independent group’s design, 34 runners
(~16 previous marathons completed) consumed either BTJ or an isocaloric placebo (PLA) for
3 days following a marathon. Maximal isometric voluntary contractions (MIVC),
countermovement jumps (CMJ), muscle soreness, serum cytokines, leucocytosis, creatine
kinase (CK), high sensitivity C-reactive protein (hs-CRP) and aspartate aminotransferase
(AST) were measured pre, post, and on the 2 days after the marathon. CMJ and MIVC were
reduced after the marathon (P<0.05) but no group differences were observed (P>0.05).
Muscle soreness was increased in the day after the marathon (BTJ; 45±48 vs. PLA; 46±39
mm) and had returned to baseline by day 2, irrespective of supplementation (P=0.694).
Cytokines (Interleukin-6; IL-6, interleukin-8, tumour necrosis factor-α) were increased
immediately post-marathon but apart from IL-6 had returned to baseline values by day 1 post.
No interaction effects were evident for IL-6 (P=0.213). Leucocytes increased 1.7 fold after
the race and remained elevated 2 days post, irrespective of supplement (P<0.0001). CK
peaked at 1 day post marathon (BTJ: 965±967 & PLA: 1141±979 IU·L-1) and like AST and
hs-CRP, was still elevated 2 days after the marathon (P<0.05); however, no group differences
were present for these variables. Beetroot juice did not attenuate inflammation or reduce
muscle damage following a marathon, possibly because most of these indices were not
markedly different from baseline values in the days after the marathon.