The effect of dietary nitrate supplementation on performance in trained male flatwater kayakers

Previous studies have reported that supplementation with nitrate-rich beetroot juice (BR) reduces the oxygen cost (VO2) of submaximal cycling and running exercise and improves both exercise capacity and performance. To date, no study has investigated the performance effects of BR on sports which rely on the recruitment of large upper body muscle mass, such as flatwater kayaking. Purpose: To determine the effects of dietary nitrate on parameters of performance in trained male kayakers. Methods: Seven male kayakers completed four exercise trials consisting of an initial discontinuous graded exercise test to exhaustion and three performance trials using a kayak ergometer. The performance trials were composed of 15 min steady state exercise at 60% of maximum work rate, 5 × 10-second maximal sprints and, following a 5 min rest period, a 1 km time trial (TT). The first trial provided a baseline measurement and the second and third trials were preceded by ingestion of either 70 ml concentrated BR or tomato juice (placebo [PLA]) 3 h prior to exercise using a randomised cross-over design. Results: Plasma nitrate (PLA: 34.1 ± 8.3 μM, BR: 152.0 ± 14.7 μM) and nitrite (PLA: 546.5 ± 76.0, BR: 702.9 ± 73.4 nM) were higher following ingestion of BR compared to PLA (both P < 0.01). VO2 was lower in the BR trial than in the PLA trial (PLA: 35.8 ± 1.4 ml kg min−1, BR: 34.6 ± 1.1 ml kg min−1, P = 0.02). There was no difference in either peak power output in the maximal sprints (P = 0.91) or TT performance between conditions (PLA: 4.6 ± 0.3 min, BR: 4.6 ± 0.3 min, P=0.91). Conclusion: In line with previous research, ingestion of BR reduced VO2 during submaximal kayak exercise although contrastingly had no impact on kayak TT performance. These differences may be attributed to the specific physiological demands of sprint kayaking.