The Ergogenic Potential of Citrulline Malate and Beetroot Extract: Mechanisms and Implications for Exercise Performance

The Ergogenic Potential of Citrulline Malate and Beet Root Extract: Mechanisms and Implications for Exercise Performance

by Thomas Cunningham, MD

Enhancing exercise performance and promoting efficient recovery are perennial pursuits in sports science and nutrition. Athletes and fitness enthusiasts often seek ergogenic aids to gain a competitive edge or optimize training adaptations.

Among the plethora of dietary supplements marketed for improving performance, citrulline malate and beetroot extract have emerged as promising candidates due to their purported physiological effects on exercise performance.

Both compounds have demonstrated potential benefits in improving endurance, power output, and recovery in various exercise modalities. Understanding the mechanisms of action of citrulline malate and beetroot extract can provide valuable insights into their efficacy as ergogenic aids and inform evidence-based strategies for enhancing exercise performance.

This article aims to critically review the current scientific literature to elucidate the mechanisms underlying the performance-enhancing properties of these ingredients (the active ingredients in PhysiVantage SENDURE-X^®).

Citrulline Malate: Mechanisms and Performance Effects

Citrulline malate, a natural compound (found richly in watermelon) comprised of the amino acid citrulline and malic acid, has garnered attention for its potential to enhance exercise performance. Citrulline, a non-proteinogenic amino acid, plays a crucial role in the urea cycle, where it is converted into arginine, a precursor of nitric oxide (NO) synthesis. Nitric oxide is a vasodilator that enhances blood flow and nutrient delivery to exercising muscles, thereby promoting endurance and delaying fatigue.

Studies investigating the ergogenic effects of citrulline malate have reported improvements in various aspects of exercise performance, including increased endurance capacity, enhanced power output, and reduced perceptions of fatigue. These effects are thought to be mediated by the augmentation of NO production, leading to improved oxygen and nutrient delivery to active muscles. Additionally, citrulline malate may buffer intracellular acidosis through its malate component, potentially delaying the onset of muscular fatigue during high-intensity exercise.

Beetroot Extract: Mechanisms and Performance Effects

Beetroot extract, derived from the root vegetable Beta vulgaris, has gained popularity as a dietary supplement due to its high nitrate content. Inorganic nitrate, abundant in beet root extract, can be converted into nitrite and subsequently into NO via the nitrate-nitrite-nitric oxide pathway, particularly under conditions of hypoxia or low pH, such as those encountered during exercise.

The ergogenic effects of beetroot extract have been attributed to its ability to increase NO availability, leading to enhanced vasodilation, improved mitochondrial efficiency, and reduced oxygen cost during exercise. Several studies have demonstrated that supplementation with beetroot extract or its constituents, such as nitrate-rich beet juice, can improve exercise performance across various modalities, including endurance exercise, high-intensity interval training (HIIT), and team sports.

Synergistic Effects and Practical Considerations

While citrulline malate and beetroot extract operate through distinct mechanisms to enhance exercise performance, their combination may elicit synergistic effects that potentiate their ergogenic properties. By simultaneously augmenting NO production through different pathways, these supplements could theoretically enhance vasodilation, blood flow, and oxygen delivery to a greater extent than either compound alone.

Practical considerations for optimizing the ergogenic effects of citrulline malate and beetroot extract include dosage, timing of ingestion, and individual responsiveness. Optimal dosages of citrulline malate typically range from 6 to 8 grams per day (depending on weight and supplement ratio), while beetroot extract supplementation often involves consuming approximately 300 to 500 milligrams of nitrate per day (3 grams of beetroot extract). Timing-wise, consuming these supplements 30 to 60 minutes before exercise may maximize their performance-enhancing effects by ensuring peak plasma concentrations coincide with the onset of physical activity. NOTE: PhysiVantage SENDURE-X^® is the only product on the market that provides both 6 grams of citrulline malate and 3 grams of beetroot extract.

Citrulline malate and beetroot extract represent promising dietary supplements for enhancing exercise performance through their respective mechanisms of action. Citrulline malate augments NO production, promoting vasodilation and delaying fatigue during prolonged exercise, while beetroot extract increases NO availability via the nitrate-nitrite-nitric oxide pathway, improving mitochondrial efficiency and reducing the oxygen cost of exercise. Further research is warranted to elucidate the optimal dosing strategies, potential synergistic effects, and long-term implications of these supplements on exercise performance and overall health.

**** RESEARCH HIGHLIGHT ****

Combined Effects of Citrulline Plus Nitrate-Rich Beetroot Extract Co-Supplementation on Maximal and Endurance-Strength and Aerobic Power in Trained Male Triathletes: A Randomized Double-Blind, Placebo-Controlled Trial.

In this randomized double-blind placebo-controlled trial, 32 male amateur triathletes (average age 32.17 years, BMI 22.57 kg/m², 7.8% fat mass) with over 5 years of experience were studied over 9 weeks. They underwent six training sessions per week, each lasting 2.5 hours, covering 70% aerobic work, 20% strength training, and 10% core and mobility drills, totaling 135 hours of exercise.

Each athlete received a personalized nutritional plan from a registered dietitian, adjusted to their training load and personal needs, and adherence was monitored using food frequency questionnaires and seven-day dietary recalls. All participants were medically screened, ensuring no interference from diseases, medications, or other supplements, and a 2-week washout period was enforced before starting the study supplements.

Participants were divided into four groups: placebo (PLG), citrulline (CITG), nitrate-rich beetroot extract (BRG), and a combination of citrulline and beetroot (CIT-BRG). Each group took 6 capsules daily (three for each supplement) over the 9 weeks. These supplements were administered in the form of capsules, with each participant taking 6 capsules per day (3 capsules of 1 g CIT and 3 capsules of 700 mg BR). The capsules were taken in two doses per day: 2 capsules at breakfast, 2 at lunch, and 2 at dinner, for a total of 9 weeks. Performance was assessed at baseline (T1) and post-intervention (T2) using various tests: horizontal jump (HJUMP), handgrip dynamometer (DYN), 1-minute abdominal test (1-MAT), and the Cooper test for aerobic power.

Results showed improvements in muscle mass and mesomorphy for the CIT-BRG group between T1 and T2. The CIT-BRG group also exhibited significant improvements in 1-MAT, HJUMP, and the Cooper test, indicating enhanced strength and aerobic power. The combination of citrulline and beetroot supplementation demonstrated a positive trend in strength and endurance performance, though further studies with larger samples are needed to confirm these findings.

Statistical analysis using two-way repeated measures ANOVA and post-hoc tests revealed significant group-by-time interactions in estimated VO2max by the Cooper test. The CIT-BRG group showed increases in both aerobic power and strength tests, suggesting that the combination of citrulline and beetroot can improve athletic performance by enhancing muscle function, reducing fatigue, and improving nutrient delivery to muscles.