The influence of sex on the effects of inorganic nitrate supplementation on muscular power and endurance

• Published in: Journal of applied physiology (1985) 2024-10, Vol.137 (6), p.1649
• Main Authors: Ortiz de Zevallos, Joaquin, Hogwood, Austin C, Kruse, Ka'eo, De Guzman, Jeison, Buckley, Meredith, DeJong Lempke, Alexandra F, Weltman, Arthur, Allen, Jason D
• Format: Article
• Language: English
• Subjects: Adult; Dietary Supplements; Double-Blind Method; Female; Fruit and Vegetable Juices; Humans; Isometric Contraction - drug effects; Isometric Contraction - physiology; Male; Muscle Fatigue - drug effects; Muscle Fatigue - physiology; Muscle Strength - drug effects; Muscle Strength - physiology; Muscle, Skeletal - drug effects; Muscle, Skeletal - physiology; Nitrates - administration & dosage; Nitrates - blood; Nitrates - pharmacology; Nitric Oxide - metabolism; Nitrites - blood; Physical Endurance - drug effects; Physical Endurance - physiology; Sex Characteristics; Sex Factors; Young Adult
• ISSN: 8750-7587; 1522-1601; 1522-1601
• DOI: 10.1152/japplphysiol.00321.2024

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's effect 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.