No effect of acute nitrate supplementation on muscle oxygen consumption in arm and leg

Abstract

Purpose: The purpose of this thesis was to investigate the effect of acute nitrate (NO3 -) supplementation on muscle oxygen consumption (mVO2) in the vastus lateralis (VL) and the flexor digitorum superficialis (FDS) muscles. Method: In a double-blinded, placebo-controlled, crossover study, nine recreationally active men consumed an acute dose of either NO3 --rich beetroot juice (2 x 400 mg NO3-) or NO3 --depleted beetroot juice (2 x 0.35 mg NO3-) 2 h prior to a dynamic handgrip test (DHT) and a cycling test (CT). The DHT consisted of three 2-min periods of dynamic handgrip exercise at 30%, 50% and 70 % of the maximal incremental handgrip test. The CT consisted of two 5-min periods of cycling at a work rate of 50% of OBLA and 70% of MAP, where pulmonary oxygen consumption (pVO2) was measured continuously. Near infrared spectroscopy (NIRS) was measuring tissue oxygenating continuously in FDS muscle and VL muscles. Results: No effect of NO3 - supplementation were found on pVO2, blood pressure (BP) or HR after an acute dose of NO3-, nor any differences on mVO2 in FDS and VL muscles during exercise were found. Discussion: No effect was found on pVO2 despite the exercise protocol was similar to previously protocols that reported an effect. Even though, the right amount of NO3 - was used and similar test conditions for the placebo period and NO3 - period, no effect on mVO2 was observed. Conclusion: At the applied dose and protocol, no effect of acute NO3 - supplementation were found on pVO2 and BP, nor an effect on mVO2 in FDS muscle and VL muscle.