Six days of supplementation with beetroot juice was associated with reductions in the aerobic energy cost of swimming, with the effects linked to the nitrate content of the juice.
The study, performed by scientists from the University of Cagliari (Italy), the Italian Olympic Committee, the Tunisian National Centre of Medicine and Science in Sports, and the University of Tor Vergata Rome (Italy), is said to be the first to test the effects of beetroot juice supplementation in swimming.
“Results of the present research may have potentially practical applicability as it indicates that beetroot juice supplementation may be suitable to enhance exercise performance in swimming,” wrote the researchers in Nutrients.
“The fact that an increase in performance was detected only at anaerobic threshold (AT) deserves attention. It is well known that AT is more sensitive than VO2max in detecting the specificity of training and that AT should be preferentially used when evaluating swimmers’ fitness status.”
Building the science
Science to support the potential for sports nutrition and cardiovascular health benefits of beetroot juice has been building in recent years, with UK scientists leading the charge. Scientists at the University of Exeter in the UK reporting that beetroot juice may boost stamina and allow people to exercise for up to 16% longer.
The vegetable juice’s nitrate content may reduce oxygen uptake to an extent that cannot be achieved by any other known means, making exercise less tiring, according to findings published in the Journal of Applied Physiology (doi:10.1152/japplphysiol.00722.2009).
“Our study is the first to show that nitrate-rich food can increase exercise endurance,” said Professor Andy Jones, the lead researcher of that study. “We were amazed by the effects of beetroot juice on oxygen uptake because these effects cannot be achieved by any other known means, including training.”
For the new study, the researchers recruited 14 moderately trained male master swimmers. The men underwent two swimming tests: One was at the start of the study, the other after six days of consuming 500 mL per day of an organic beetroot juice.
Results showed a significant increase in the workload at anaerobic threshold after six days of beetroot juice consumption, compared with baseline control values.
In addition, the aerobic energy cost was significantly reduced after beetroot juice consumption.
On the other hand, no statistically significant effects were observed for oxygen uptake (VO2), carbon dioxide production (VCO2), or pulmonary ventilation (VE).
Boosting blood flow to muscles
“The improved swimming performance at anaerobic threshold found in the present investigation suggests that beetroot juice supplementation influences preferentially type 2 muscle fibers,” wrote the researchers. “This suggestion is in accordance with recent evidence in rats, where beetroot juice supplementation induces a marked increase in muscle blood flow during exercise with the blood flow preferentially distributed to muscle groups that principally contain type 2 fibers, which are recruited especially during moderate-high intensity exercise. Moreover, it was found that beetroot juice supplementation results in a preferential distribution of blood flow to type 2 fibers and improves oxidative functions in hypoxic muscle.”
The researchers also noted that, since the study was performed in moderately trained master athletes, it is not known if the same effects would be observed in elite swimmers, with evidence to date suggesting that elite athletes may not respond to the same extent, they said.
“This may relate to factors such as greater nitric oxide synthase activity, better muscle oxygenation and mitochondrial efficiency, and a lower fraction of type II fibers in the muscles of highly trained, compared with moderately trained, individuals.”
2014, Volume 6, Number 2, Pages 605-615, doi:10.3390/nu6020605
“Effect of Beetroot Juice Supplementation on Aerobic Response during Swimming”
Authors: M. Pinna, S. Roberto, R. Milia, E. Marongiu, S. Olla, et al.