No effect of dietary nitrate supplementation on endurance training in hypoxia

We investigated whether dietary nitrate (NO3-) supplementation enhances the effect of training in hypoxia on endurance performance at sea level. Twenty-two healthy male volunteers performed high-intensity endurance training on a cycle ergometer (6 weeks, 5x30min/week at 4-6mmol/L blood lactate) in normobaric hypoxia (12.5% FiO(2)), while ingesting either beetroot juice [0.07mmol NO3-/kg body weight (bw)/day; BR, n=11] or a control drink (CON, n=11). During the pretest and the posttest, the subjects performed a 30-min simulated time trial (TT) and an incremental VO2max test. Furthermore, a biopsy was taken from m. vastus lateralis before and after the TT. Power output during the training sessions in both groups increased by approximate to 6% from week 1 to week 6 (P<0.05). Compared with the pretest, VO2max in the posttest was increased (P<0.05) in CON (5%) and BR (9%). Power output corresponding with the 4mmol/L blood lactate threshold, as well as mean power output during TT increased by approximate to 16% in both groups (P<0.05). Muscle phospho-AMP-activated protein kinase, hypoxia inducible factor-1 mRNA content, and glycogen breakdown during the TT were similar between the groups in both the pretest and the posttest. In conclusion, low-dose dietary NO3- supplementation does not enhance the effects of intermittent hypoxic training on endurance exercise performance at sea level.