Repeated-sprint performance and plasma responses following beetroot juice supplementation do not differ between recreational, competitive and elite sprint athletes - Jonvik, K. L.; Nyakayiru, J.; Van Dijk, J. W.; Maase, K.; Ballak, S. B.; Senden, J. M. G.; Van Loon, L. J. C.; Verdijk, L. B. (European Journal of Sport Science, 2018)