Physiological and performance effects of nitrate supplementation during roller-skiing in normoxia and normobaric hypoxia

The present study examined the effects of acute nitrate (NO₃^-) supplementation ingested in the form of concentrated beetroot juice on cross-country roller-ski performance in normoxia (N) and normobaric hypoxia (H). Eight competitive cross-country skiers (five males: age 22 ± 3 years, V·O_2max 71.5 ± 4.7 mL kg^-1·min^-1; three females: age 21 ± 1 years, V·O_2max 58.4 ± 2.5 mL kg^-1·min^-1) were supplemented with a single dose of NO₃^--rich beetroot juice (BRJ, ∼13 mmol NO₃^-) or a NO₃^--depleted placebo (PL, ∼0 mmol NO₃^-) and performed 2 x 6-min submaximal exercise bouts and a 1000-m time-trial (TT) on a treadmill in N (20.9% O₂) or H (16.8% O₂). The four experimental trials were presented in a randomised, counter-balanced order. Plasma NO₃^- and nitrite concentrations were significantly higher following BRJ compared to PL (both p < 0.001). However, respiratory variables, heart rate, blood lactate concentration, ratings of perceived exertion, and near-infrared spectroscopy-derived measures of muscle tissue oxygenation during submaximal exercise were not significantly different between BRJ and PL (all p > 0.05). Likewise, time to complete the TT was unaffected by supplementation in both N and H (p > 0.05). In conclusion, an acute dose of ∼13 mmol NO₃^- does not affect physiological or performance responses to submaximal or maximal treadmill roller-skiing in competitive cross-country skiers exercising in N and H.