Project follows a pilot study - Blood nitrate/nitrite dynamics after beetroot juice concentrate intake (MUNI/A/0977/2017). Collected data from this study are the key basis for our submitted project. The aim of our planned research is to observe the effects of intake of beetroot juice concentrate with high dietary nitrate content on physical performance in two groups of athletes. The research also focuses on presumption that every athlete has different baseline levels of blood nitrites/nitrates which might be related to fitness level of each athlete and thereafter could have impact on reaction to supplementation in context of improvement/impairment of performance. Research will therefore be carried out on two different groups of athletes divided by their fitness level and baseline levels of blood nitrates/nitrites.