Effects of Citrulline Malate and Beetroot Juice Supplementation on Energy Metabolism and Blood Flow During Submaximal Resistance Exercise

Abstract

The ergogenic effects of citrulline malate (CitMal) and beetroot juice (BEET) have been widely studied, but their effects on physiological outcomes related to resistance exercise are not fully understood. The purpose of this randomized, double-blind, crossover study was to investigate the effects of CitMal (8 g) and BEET (400 mg nitrate) on blood pressure (BP), blood flow, and energy efficiency during submaximal leg extension. Recreationally active males (n = 27; age: 22 ± 4 yrs) completed familiarization, followed by three testing visits. Supine and standing BP were measured upon arrival, followed by supplement ingestion, a 2-h rest period, postsupplement BP measurement, and a bout of repeated submaximal isotonic leg extensions at 25% of maximal voluntary contraction torque. Diameter (aDIAM) and blood flow (aBF) of the superficial femoral artery, and cross-sectional area (CSA) and echo intensity (EI) of the vastus lateralis, were measured before and after exercise via ultrasonography. Muscle blood flow (mBF) and oxygen consumption (mVO₂), along with whole-body energy expenditure (EE) and respiratory exchange ratio (RER), were measured before and during exercise via indirect calorimetry and near-infrared spectroscopy. Baseline RER values differed among treatments (p = 0.01); BEET was higher than CitMal (p = 0.01) but not PLA (p = 0.58); CitMal and PLA were not significantly different (p = 0.12). No other measurements were significantly affected by treatment (all p > 0.05). Results suggest that neither CitMal nor BEET significantly influence resting BP, blood flow, or metabolic efficiency during submaximal leg extension in recreationally active males.

Keywords:

• energy efficiency
• exercise hyperemia
• leg extension
• nitric oxide
• oxygen consumption
• vasodilation

Acknowledgments

The authors thank Shawn Ahuja and Casey Greenwalt for their assistance and all of the research participants for their time and effort.

Declaration of interest

The authors declare no conflicts of interest. The authors alone are responsible for the content and writing of the article.

Additional information

Funding

The current study was funded by the National Strength and Conditioning Association Foundation.

Notes on contributors

Eric T. Trexler

Eric T. Trexler, PhD, is a research assistant in the Applied Physiology Laboratory at the University of North Carolina at Chapel Hill.

Dale S. Keith

Dale S. Keith, BA, is a research assistant in the Applied Physiology Laboratory at the University of North Carolina at Chapel Hill.

Adam A. Lucero

Adam A. Lucero, BSc, is a doctoral candidate in the School of Sport, Exercise and Nutrition at Massey University.

Lee Stoner

Lee Stoner, PhD, is an assistant professor of exercise physiology at the University of North Carolina at Chapel Hill.

Todd A. Schwartz

Todd A. Schwartz, PhD, is a research associate professor of biostatistics at the University of North Carolina at Chapel Hill.

Adam M. Persky

Adam M. Persky, PhD, is a clinical professor of pharmacy at the University of North Carolina at Chapel Hill.

Eric D. Ryan

Eric D. Ryan, PhD, is an associate professor of exercise physiology at the University of North Carolina at Chapel Hill.

Abbie E. Smith-Ryan

Abbie E. Smith-Ryan, PhD, is an associate professor of exercise physiology and director of the Applied Physiology Laboratory at the University of North Carolina at Chapel Hill.