Inorganic nitrate ([Formula: see text]) supplementation increases nitric oxide (NO) bioavailability and may improve muscular power and endurance, although most studies are in males. Therefore, the present double-blind, randomized, placebo-controlled study examined the effects of [Formula: see text] supplementation on isokinetic peak power, maximal voluntary isometric contraction (MVIC) force, muscular endurance (time-to-task failure; TTF), and recovery from fatigue in young females (= 12) and males (= 14). Participants consumed ∼13 mmol [Formula: see text] [beetroot juice (BRJ)], or an identical [Formula: see text]-depleted beverage placebo (PL), for ∼3 days and 2 h before testing visits. Plasma nitrate and nitrite were elevated in the BRJ condition (≤ 0.05). Peak power (W·kg) showed a sex effect (≤ 0.05) at all angular velocities and a sex-by-treatment effect at 270 and 360°/s (≤ 0.05). Post hoc analysis revealed no significant differences between treatments (> 0.05). Estimated maximal knee extension power () and maximal knee extension velocity () demonstrated no sex, treatment, or sex-by-treatment effect (> 0.05). There were no significant effects for TTF (F: PL; 269 ± 161 vs. BRJ; 277 ± 158 s and M: PL; 228 ± 171 vs. BRJ; 194 ± 100 s;> 0.05). Cohen'seffect sizes for peak power showed moderate to large effect sizes at 270 (= 0.92) and 360°/s (= 0.81), showing a possible differentiated effect of dietary nitrate in females and males. The present data indicate that [Formula: see text] supplementation does not significantly affect knee extensor maximal power, maximal contraction velocity, and muscular endurance in either sex. The sex-dependent response to dietary nitrate supplementation requires further investigation as data on females is scarce.Recent data have suggested that inorganic nitrate ([Formula: see text]) supplementation may benefit males; however, females may experience worsened endurance capacity. This study revealed a potential differentiated effect of [Formula: see text] supplementation on outcomes of muscle contractile function between healthy, young males and females. The specific responses of [Formula: see text] supplementation in females and across sexes remain understudied and require further investigation. n n P P P P P V P P d d d -1max max NEW & NOTEWORTHY
