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

Abstract

Background Aging 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.Methods Twelve 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 NO3and NO2and breath NO were measured periodically, and muscle function was determined using isokinetic dynamometry.Results NO3ingestion 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%.Conclusions Acute dietary NO3intake 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.

Dose-response effect of dietary nitrate on muscle contractility and blood pressure in older subjects

“…Muscle contractile function: There were no significant effects of NO 3 ingestion on knee extensor peak torque, and hence peak power, at low to moderate angular velocities (i.e., at 0, 1.57, 3.14, or 4.71 rad/s; Table 2). In keeping with our previous results (16), however, ingestion of BRJ containing a moderate amount of NO 3 -(i.e., 200 µmol/kg) resulted in a significant increase in peak torque, and hence peak power, at the highest velocity tested (i.e., 6.28 rad/s) ( -D).…”

“…5 mmol (182±10 µmol/kg) of NO 3 increased maximal knee extensor speed and power by 11±2 and 4±4%, respectively(16). The results of the present study are similar, in that Vmax and Pmax improved by 8±4 and 7±3%, respectively, after ingestion of BRJ containing 200 µmol/kg of NO 3 -.…”

“…We have previously demonstrated that dietary NO 3 − supplementation can enhance muscle contractility in a variety of subject populations (11–14). This includes healthy elderly men and women, in whom acute intake of 13.4±0.5 mmol (182±10 µmol/kg) of NO 3 − increased maximal knee extensor speed and power by 11±2 and 4±4%, respectively (16). The results of the present study are similar, in that Vmax and Pmax improved by 8±4 and 7±3%, respectively, after ingestion of BRJ containing 200 µmol/kg of NO 3 − .…”

“…The required sample sizes to detect changes in Pmax and Vmax (the primary outcome variables) were estimated based on the respective effect sizes observed in our recent study (16) and assuming = 0.05 and 1- = 0.90. These calculations indicated that n = 11 would be required to detect changes in Pmax, whereas n = 6 would be required to detect changes in Vmax.…”

“…Although the exact mechanisms responsible for this effect are still uncertain, they appear to involve NO-mediated changes in muscle calcium (Ca 2+ ) release and/or sensitivity (15). More recently, we have demonstrated that acute NO 3 − ingestion also significantly improves muscle speed and power in healthy elderly subjects (16). These changes were large enough to theoretically offset the reductions resulting from several decades of aging.…”