Dietary nitrate does not alter the rate of torque development during maximal voluntary isometric or electrically evoked tetanic contractions in young men or women

Abstract

We determined the effects of NO3- ingestion on voluntary and electrically evoked rate of torque development (RTD) in young men and women. Using double-blind, placebo-controlled crossover designs, 14 men or 12 women (tested during both early and late follicular phases) acutely ingested 200 mol/kg of NO3- from beetroot juice (BRJ) or a NO3--free BRJ placebo. Voluntary RTD (0 30 ms, 0 50 ms, 0-200 ms, maximal) was measured during maximal voluntary isometric contractions. The maximal tetanic RTD was also determined during stimulation at 100 Hz. Muscles tested included the triceps surae and triceps brachii in men and the quadriceps femoris in women. Dietary NO3- had no significant effect on initial or maximal voluntary RTD in men in either muscle group (P[≥]0.31) or in women during either menstrual phase (P[≥]0.69). Similarly, acute NO3- intake did not alter maximal tetanic RTD in men (P[≥]0.87) or women (P[≥]0.70). We conclude that acute dietary NO3- supplementation has no apparent effect on RTD during maximal voluntary or electrically evoked isometric contractions of the lower or upper limbs in young, untrained individuals. These findings argue against changes in neural activation or actomyosin crossbridge cycling rate as mechanisms driving NO3--induced improvements in muscle contractile function.