Data on positive influence of dietary nitrate supplementation in the form of beetroot extract on reduced oxygen cost of sub-maximal exercise and enhanced tolerance to high intensity exercise further paved way for more studies, where role of beetroot extract in enhancing performance of various forms of sports and athletics was evaluated.
In a randomized, double-blind, crossover study involving nine healthy, non-smoking volunteers (mean age: 30±2.3 years), effects of dietary nitrate on various physiological and biochemical parameters during maximal exercise was evaluated. In this study, volunteers were provided dietary supplementation with nitrate (0.1 mmol/kg/day), equivalent to the amount found in 100–300 g of a nitrate-rich beetroot or placebo (NaCl) for 2 days before the test.
The test consisted of an incremental exercise to exhaustion with combined arm and leg cranking on two separate ergometers. Results demonstrated that nitrate supplementation resulted in reduced oxygen consumption, while time to exhaustion trended to an increase.
As it has been commonly known that during heavy exercise, the body reaches its maximum capacity to consume oxygen, and dietary nitrate was found to reduce this maximum capacity to consume oxygen, without affecting the increase in exhaustion time. Hence, it was concluded that a correlation exists between the change in time to exhaustion and the change in maximum oxygen consumption, which may be attributed to usage of large active muscle mass during maximal exercise (Larsen et al., 2010).
It has been well understood that dietary nitrate supplementation helps reduce the oxygen cost of sub-maximal exercise and to improve high-intensity exercise tolerance, but whether it also enhances the performance during simulated competition, such as cycling is yet unknown.
Hence, to ascertain the influence of acute dietary nitrate supplementation on power output oxygen cost and performance during 4 and 16.1 km cycling time trials a study with randomized, crossover design was carried out in nine male cyclists.
After familiarization, all cyclists were asked to consume 500 ml of beetroot juice (BR; ~6.2 mmol of nitrate) or 500 ml of placebo (PL), around 2.5 h before the completion of 4 and 16.1 km cycling time trial. Results indicated that BR significantly increased mean power output during the 4 km and 16.1 km cycling time trial.
Further, improvement in both 4 km and 16.1 km performance by 2.8% and 2.7%, respectively, was seen in BR group.
Adapted from Lansley et al., Med Sci Sports Exer. 2011
Finally, from the study results it was concluded that acute dietary nitrate supplementation with beetroot juice may enhance the performance during simulated competition (Lansley et al., 2011).
Although acute dietary nitrate supplementation with beetroot juice has been known to reduce pulmonary oxygen uptake during sub-maximal exercise and enhanced tolerance of high-intensity work rates, not enough data is available on the effect of nitrate ingestion on athletic performance—the potential ergogenic effects.
Hence, a double-blind, repeated-measures crossover design study was conducted in 12 male trained cyclists (mean age: 31±3 years) with the hypothesis that acute intake of nitrate supplementation with concentrated dose of beetroot juice would improve time-trial performance.
The participants were provided with 140 ml/day of concentrated beetroot juice (~8 mmol/day nitrate) or a placebo for 6 days, separated by a 14-day washout period. On day 6, all trained cyclists were asked to perform 60 min of sub-maximal cycling, followed by 10 km time trial. At the end of the study, it was observed that beetroot extract improved both the time trial performance and power output compared to the placebo (Cermak et al., 2012).