Participants in the study, who were all university team-sport players, consumed either beetroot juice (BTJ) or a placebo after completing a sprint test. Researchers recorded the results of tests including countermovement jumps and reactive strength, along with blood tests.
Reduced muscle pain, better recovery
“Consuming BTJ for four days after a muscle damaging [repeated sprint test] attenuated muscle pain and decrements in dynamic muscle function, as measured by [countermovement jumps] and [reactive strength index]. These effects did not translate to improved recovery of isometric strength or sprint performance however,” wrote the authors in the journal Nutrients.
Participants consuming beetroot juice had countermovement jump heights 7.6% higher than the placebo group 72 hours after the sprint test, and their reactive strength index was higher than the placebo group at all points.
The researchers suggested beetroot juice could be effective as part of a post-exercise recovery strategy, but said it was unclear what real-world impact this would have.
They also called for further investigations, as “the beneficial effects of BTJ were shown to be unrelated to systemic changes in oxidative stress or other biochemical markers of muscle damage”.
No evidence for anti-oxidant effect
This was in contrast to their initial prediction that antioxidant elements of beetroot juice would be beneficial to post-exercise recovery – particularly the betalain pigments which give the juice its colour.
“Due to the fact that oxidative stress has been associated with muscle damage after eccentric-heavy exercise, and that beetroot and its constituents have been shown to act as antioxidants, we hypothesised that BTJ could attenuate muscle damage by protecting cells against oxidative stress,” the authors wrote.
“However, our findings do not support this contention. We found no evidence that BTJ attenuated oxidative stress as both indirect markers (lipid hydroperoxides and protein carbonyls) and a direct marker of free radical production were not different between the BTJ and [placebo] groups at all-time points,” they added.
This was in contrast to previous research that showed antioxidant-rich supplements reduced oxidative stress. However their study showed only a modest increase in lipid hydroperoxides shortly after the sprint tests, and no other evidence to suggest antioxidant effects.
“[This study] suggests that mechanisms other than antioxidant effects were possibly involved. It was beyond the scope of this study to examine the role of other mechanisms by which BTJ could attenuate muscle damage, but owing to the seemingly pleotropic nature of phenolic and betalainic compounds and [nitric oxide], there are a number of possible candidates,” they said.
The study was part of a doctoral degree which receives financial support from Gs Fresh Ltd, a vegetable grower, which supplied the supplements for the study.
The authors said the company had no involvement in any other element of the study, and declared no conflicts of interest.
Published online ahead of print, doi: 10.3390/nu8080506
“Effects of Beetroot Juice on Recovery of Muscle Function and Performance between Bouts of Repeated Sprint Exercise”
Authors: Clifford, T.; Berntzen, B.; Davison, G.W.; West, D.J.; Howatson, G.; Stevenson, E.J.