The Effect of Beetroot Juice Supplementation on Dynamic Apnea and Intermittent Sprint Performance in Elite Female Water Polo Players Kristin L. Jonvik Maastricht University and HAN University of Applied Sciences Jan-Willem van Dijk HAN University of Applied Sciences Joan M.G. Senden Maastricht University Luc J.C. van Loon Maastricht University and HAN University of Applied Sciences Lex B. Verdijk Maastricht University Nitrate-rich beetroot juice is thought to have ergogenic effects, particularly in conditions where oxygen availability is limited. Whether these effects also apply to elite athletes is currently unknown. The aim of this study was to assess the effects of beetroot juice supplementation on dynamic apnea and intermittent sprint performance in elite female water polo players. In a double- blinded, randomized, crossover manner, the Dutch National female water polo team (N = 14) was subjected to two 6-day supplementation periods (1 and 2), with either 140 ml/day of nitrate-rich (BR; ∼800 mg/day nitrate) or nitrate-depleted (PLA) beetroot juice. Following blood sampling on Day 6, the athletes performed a maximal-distance front crawl swimming test without breathing (dynamic apnea test). In addition, intermittent sprint performance was assessed by performing 16 swim sprints of 15 m, in a 4 × 4 block with 30-s recovery between blocks (intermittent test). Distance covered during the dynamic apnea test did not differ between BR (49.5 ± 7.8 m) and PLA (46.9 ± 9.1 m, p = .178). However, when correcting for test order, the distance covered was significantly larger in BR versus PLA when BR was ingested in Period 2 (50.1 ± 8.5 vs. 42.8 ± 5.7 m, p = .002), whereas no difference was observed when BR was ingested in Period 1 (48.8 ± 7.4 vs. 52.3 ± 10.4 m, p = .10). The time to complete the intermittent test was not different between BR and PLA (316.0 ± 7.9 vs. 316.3 ± 6.9 s, p = .73). In conclusion, beetroot juice supplementation does not improve intermittent performance in elite female water polo players, but there may be a potential for ergogenic effects during dynamic apnea. Keywords: ergogenic, nitrate, nitrite Over the past decade, the use of dietary nitrate to enhance performance has received increased attention, with possible ergo- genic effects being caused by the reduction of dietary nitrate into nitrite and nitric oxide (Lundberg et al., 2008). Nitric oxide plays a key role in skeletal muscle function—for example, by regulating blood flow and muscle contractility (Stamler & Meissner, 2001). Hypoxic conditions with low oxygen availability and a low pH environment can stimulate the nitrate–nitrite–nitric oxide pathway (Jones, 2014). Several studies have found ergogenic effects of nitrate sup- plementation when exercising under hypoxic conditions. This could be “local” tissue hypoxia, such as during anaerobic, high- intensity intermittent exercise (Nyakayiru et al., 2017; Thompson et al., 2016; Wylie et al., 2013), or “systemic” normobaric/ hypobaric hypoxia (Carriker et al., 2016; Vanhatalo et al., 2010). Although “systemic hypoxia” has also been used with respect to maximal underwater exercise (Schagatay, 2010), the term “dynamic apnea” more appropriately reflects the different physiological characteristics associated with these breath-holding activities. Interestingly, recent work suggests that dietary nitrate may also prove beneficial under conditions of dynamic apnea (Patrician & Schagatay, 2017). Jonvik, Senden, van Loon, and Verdijk are with the NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University, Maastricht, The Netherlands. Verdijk is also with the Dept. of Human Movement Sciences, Maastricht University Medical Centre, Maastricht, The Netherlands. Jonvik, van Dijk, and van Loon are with the Institute of Sports and Exercise Studies, HAN University of Applied Sciences, Nijmegen, The Netherlands. Address author correspondence to Lex B. Verdijk at lex.verdijk@maastrichtuniversity.nl. 468 International Journal of Sport Nutrition and Exercise Metabolism, 2018, 28, 468-473 https://doi.org/10.1123/ijsnem.2017-0293 © 2018 Human Kinetics, Inc. RAPID COMMUNICATION