Effects of nitrate supplementation on running performance in subjects with different fitness level

Introduction. Several recent studies indicate that dietary nitrate supplementation reduces O2 cost of exercise and improves exercise tolerance (Bailey et al. 2009, Larsen et al. 2010, Lansley et al. 2011). However, data have been provided that well-trained endurance athletes do not benefit from NO3- supplementation (Bescos et al. 2011, Christensen et al. 2013). The aim of this study was to evaluate the effects of short-term NO3- supplementation on running performance in subjects with different level of fitness. Material and methods. Fourteen subjects (age 22.6 ± 2.3 years) with different fitness level (VO2peak value ranging from 38.78 to 61.68 ml*kg-1*min-1) participated in a randomized double-blind placebo-controlled study. Each subject was tested after 6 days of supplementation with either 0.5 l per day of nitrate-conteining water (5.0 mol/day nitrate) (NITR) or nitrate-free water (PLA). Participants performed an incremental running test until exhaustion and three repetitions of 5-min sub-maximal (about 60% VO2max) constant load tasks on a motorized treadmill. The best 3-km running time-trial performance on the field was also recorded. Results. Plasma [NO3-] was 12.2 ± 4.72 μM and 70.7 ± 4.1 μM in PLA and NITR respectively. VO2peak was not significantly different between PLA (53.7 ± 7.69 ml*kg-1*min-1) and NITR (54.0 ± 7.55 ml*kg-1*min-1). During sub-maximal tests the O2 consumption was lower in NITR (31.8 ± 2.31 ml*kg-1*min-1) than in PLA (32.9 ± 2.44 ml*kg-1*min-1). As for 3-km, in NITR the best performance time (737.8 ± 147.2 sec) was significantly lower than in PLA (757.7 ± 153.2 sec). A significant relationship between VO2peak and VO2 at steady state during constant load task and 3-km time-trial performance was observed. Conclusion. The results of the present study suggest that the individual fitness level can affect the ergogenic benefits induced by dietary nitrate supplementation. More data are needed to clarify this issue.