We looked at the paper below for this sport science journal club. It focused on the effects of beetroot (BR) juice on running and walking.
What was the aim of the paper?
Beetroot juice has previously been shown to reduce resting blood pressure, and the oxygen cost of submaximal exercise. Research has also shown that it can increase tolerance to high intensity cycling. The researchers had three main aims for this study:
1. Were the physiological effects of BR due to the high nitrate content?
2. How much of the increase of nitrate bioavailability with BR may increase mitochondrial biogenesis (process by which new mitochondria are formed in the cells)?
3. Extend the previous findings to walking and running.
The researchers hypothesised that BR supplementation would increase plasma nitrate and reduce blood pressure, reduce oxygen cost of walking and running and increase exercise tolerance and increase muscle oxidative capacity. The researchers were from the University of Exeter.
What did the study involve?
Nine men were recruited for the study and after the researchers determined their VO2 max and the participants completed ‘step’ running tests, they were assigned to either consume 0.5 l/day of nitrate rich BR (containing around 6.2 mmol of nitrate) or nitrate depleted BR for 6 days. During days 4 and 5, participants repeated the step running tests and on day 6 they performed knee-extension exercise tests. The participants were told to drink the BR slowly, 3 hours before exercise.
What were the main results?
The researchers found that mitochondrial oxidative capacity was not different between placebo and beetroot but the oxygen cost of walking, moderate intensity running and severe intensity running was reduced by BR. They also found that time to exhaustion during severe intensity running was increased.
What can we take from it?
This was a really interesting and very in-depth study that adds to what we already know about BR juice and exercise. The findings suggest that short-term dietary supplementation with nitrate rich BR juice reduced the oxygen cost of walking and moderate and severe running, and increased time to exhaustion. An important point in this study was that the researchers were able to use nitrate depleted placebo juice, which made sure that the protocol was double-blind and the participants did not know which juice they were drinking. The researchers believe that the results may be important for people with cardiovascular problems as the BR was shown to reduce the oxygen cost of walking, which may significantly improve their quality of life.
I really enjoyed reading this study and thought it was well written and included lots of detail, such as the subjects abstaining from using chewing gum throughout the study. The use of the randomised, crossover design ensured that the participants acted as their own controls which helped to reduce bias. I liked the use of illustrations to show the exercise test protocol and the tables and figures. I’m looking forward to reading more research in this area. The author from this paper has answered a number of questions about his research for sport science journal club, which you can read here.