Impact of Red Spinach Extract Supplementation on Bench Press Performance, Muscle Oxygenation, and Cognitive Function in Resistance-Trained Males.

James T Haynes Iv,Adam M Gonzalez,Matthew D Ruiz,Jeremy R Townsend,Megan D Jones,Kent D Johnson,Laurel A Littlefield,Marko A Aziz

doi:10.3390/sports9060077

Abstract

The purpose of this study was to assess the impact of short-term dietary nitrate supplementation, in the form of red spinach extract (RSE), on bench press performance, muscle oxygenation, and cognitive function in resistance-trained males. Ten resistance-trained males participated in this randomized, cross-over, placebo-controlled, double-blind investigation. Each participant completed 7 days of either RSE (2 g; 180 mg NO3−) or a maltodextrin placebo (PL) in a counterbalanced fashion with a 14-day washout between treatments. During experimental visits, participants were provided their 8th and last dose of RSE or PL 40 min before completing 5 sets of the barbell bench press exercise to failure at 75% of a predetermined 1-repetition maximum with 2 min rest intervals. Mean and peak power were recorded via a linear transducer. Near-infrared spectroscopy (NIRS) was implemented to estimate muscle oxygenation, a Stroop Test was used to assess cognitive function, and subjective performance ratings were obtained in relation to the acute resistance exercise sessions. Data were analyzed via separate repeated measures analyses of variance. There were no time by group interactions for bench press repetitions (p = 0.549), peak power (p = 0.061), or mean power (p = 0.877) across the 5 sets of bench press. Additionally, no significant differences (p > 0.05) were observed for any measure of muscle oxygenation, Stroop performance, or subjective performance ratings. It appears that 7 days of RSE supplementation did not alter performance, muscle oxygenation, nor Stroop scores during or following the bench press exercise in resistance-trained males.

Highlights

Nitric oxide (NO) is a molecule produced by the body which stimulates a variety of actions including vasodilation [1], improved calcium handling [2], improved exercise economy [3], and increased velocity of skeletal muscle contractions [4]
Heart Rate and Blood Pressure There was no time by group interaction for heart rate (HR) (p = 0.301, η2 = 0.064); there was a main effect for time (p < 0.001, η2 = 0.844) with HR declining from baseline to postexercise (p < 0.001)
Our results indicate that supplementing with 2 g of red spinach extract (RSE) for 7 days has no significant effect on number of repetitions completed, peak power, and mean power during fatiguing upper-body resistance exercise

Summary

Introduction

Nitric oxide (NO) is a molecule produced by the body which stimulates a variety of actions including vasodilation [1], improved calcium handling [2], improved exercise economy [3], and increased velocity of skeletal muscle contractions [4]. NO3− is converted to nitrite (NO2−) via anaerobic bacteria on the surface of the tongue and through the NO3− -NO2− pathway, NO2− is eventually reduced to produce NO which can elicit its biological effects on various cells in the body [6]. Through these mechanisms, dietary NO3− supplementation has been shown to improve exercise performance by improving muscle’s ability to use oxygen [7], time-trial performance [8], and high-intensity intermittent running performance [9]. Some data suggests that NO3− -rich foods can enhance cerebral perfusion to areas of the brain responsible for executive functioning [13], which may enhance cognition during and following fatiguing exercise [14,15]

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