A single dose of dietary nitrate increases maximal muscle speed and power in healthy older men and women

Abstract

BackgroundAging results in reductions in maximal muscular strength, speed, and power, which often lead to functional limitations highly predictive of disability, institutionalization, and mortality in the elderly. This may be partially due to reduced nitric oxide (NO) bioavailability. We therefore hypothesized that dietary nitrate (NO3-), a source of NO via the NO3- [->] nitrite (NO2-) [->] NO enterosalivary pathway, could increase muscle contractile function in older subjects. MethodsTwelve healthy older (age 71{+/-}1 y) subjects were studied using a randomized, doubleblind, placebo-controlled, crossover design. After fasting overnight, subjects were tested 2 h after ingesting beetroot juice containing or devoid of 13.4{+/-}0.5 mmol NO3-. Plasma NO3- and NO2- and breath NO were measured periodically, and muscle function was determined using isokinetic dynamometry. ResultsNO3- ingestion increased (P<0.001) plasma NO3-, plasma NO2-, and breath NO by 1050%, 140%, and 110%, respectively. Maximal velocity of knee extension increased (P<0.01) by 1.1{+/-}0.3 rad/s, or by 10.9{+/-}3.5%. Maximal knee extensor power increased (P<0.05) by 0.14{+/-}0.06 W/kg, or by 4.4{+/-}2.3%. ConclusionsAcute dietary NO3- intake improves muscle contractility in older individuals. These findings have important implications for this population, in whom diminished muscle function can lead to functional limitations, dependence, and even premature death.