No effect of beetroot juice supplementation on exercise economy and performance in recreationally active females despite increased torque production

This study investigated the effects of acute and chronic beetroot juice ( BRJ ) supplementation on submaximal exercise oxygen uptake ( VO 2 ), time trial ( TT ) performance, and contractile properties of the plantar flexors in females. Study 1: Using a double blind, randomized, crossover design, 12 recreationally active females using hormonal contraceptives supplemented acutely (2.5 h) and chronically (8 days) with 280  mL BRJ /d (~26 mmoles nitrate [ NO 3 − ]) or a NO 3 − ‐free placebo ( PLA ). On days 1 and 8, participants cycled for 10 min at 50% and 70% VO 2peak and completed a 4  kJ /kg body mass TT . Plasma [ NO 3 − ] and nitrite ([NO 2 − ]) increased significantly following BRJ supplementation versus PLA . There was no effect of BRJ supplementation on VO 2 at 50% or 70% VO 2peak , or TT performance. Study 2: 12 recreationally active females ( n  = 7 from Study 1) using hormonal contraceptives participated in a baseline visit and were supplemented acutely (2.5 h) and chronically (8 days) with 280  mL BRJ /d. Maximum voluntary strength ( MVC ) of the plantar flexors was assessed and a torque‐frequency curve performed. BRJ had no effect on MVC , voluntary activation, peak twitch torque, time to peak torque, or half relaxation time. Following both acute (46.6 ± 4.9% of 100 Hz torque) and chronic (47.2 ± 4.4%) supplementation, 10 Hz torque was significantly greater compared to baseline (32.9 ± 2.6%). In summary, BRJ may not be an effective ergogenic aid in recreationally active females as it did not reduce submaximal exercise VO 2 or improve aerobic TT performance despite increasing low frequency torque production.