Us runners and endurance athletes are always looking for ways to improve - be it faster times, longer distances, faster recovery, or easier sessions. While training regimens, diet, equipment and glycogen management are crucial and by now are established practice in the community, various supplements have gained attention in the past decade for their potential to improve endurance and stamina. Among these, L-citrulline stands out as a naturally occurring compound that has been researched across a number of clinical studies.
What is L-citrulline?
L-citrulline is a naturally occurring amino acid, meaning that the body can produce it on its own to some extent. L-citrulline serves as a key precursor to another amino acid, L-arginine, which plays a crucial role in the production of nitric oxide (NO) in the body.
How does nitric oxide (NO) contribute to endurance?
Nitric oxide is a vasodilator, meaning it relaxes and widens blood vessels, improving blood flow and nutrient delivery throughout the body. For us endurance athletes, this means:
- Improved Oxygen Delivery: Increased blood flow makes sure muscles receive enough oxygen during exercise, delaying the onset of fatigue and allowing athletes to sustain higher levels of performance.
- Reduced Fatigue: By facilitating the removal of metabolic waste products such as lactic acid, nitric oxide helps reduce muscle fatigue and discomfort during prolonged exertion.
Scientific Evidence
Numerous studies have investigated the effects of L-citrulline supplementation on endurance exercise performance. There are two in particular that are most commonly cited given their thoughtful experiment design and conclusions:
Oral L-citrulline supplementation enhances cycling time trial performance in healthy trained men (2016):
- Faster Times: This study found that trained cyclists who consumed L-citrulline daily over a week experienced significantly improved 4km time trial performance by 1.5% compared with those who received a placebo.
- Improved Concentration: Additionally, those who consumed L-citrulline reported significantly improved subjective feelings of muscle fatigue and concentration immediately after exercise.
L-Citrulline supplementation improves O2 uptake kinetics and high-intensity exercise performance in humans (2015):
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Power Output: This study of 10 active adults found that power output (measured in watts) was significantly higher for those who consumed L-citrulline daily for a week during a 60-second all-out cycle sprint done at the end of a 6 minute workout.
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Improved VO2 kinetics: This study also observed a significantly improved VO2 uptake mean response time in the group supplementing with L-citrulline. Improved VO2 kinetics increases the overall amount of work that can be done at high intensities before fatigue hits, which can help in competition performance and overall training effectiveness.
How to add L-citrulline into your daily regimen
Incorporating L-citrulline supplementation into your diet can be great step towards enhancing endurance and optimizing performance. However, it's essential to consider the following:
- Ensure Effective Dosage: Make sure that products include enough dosage to be effective. It's unfortunately a common practice of brands to try to cut costs by reducing the amount of effective ingredients. While every body is different, studies that have shown positive results have used a minimum dose of 2 grams per day.
- Be Consistent: Based on results from studies which all incorporate daily supplementation over time, L-citrulline may require consistency of dosage to yield noticeable benefits.
- Quality: Opt for supplements that have been tested by third-party organizations and are transparent with their supplement facts and ingredient lists to ensure potency and quality.
Our Stamina 13 performance blend includes 2,400mg of L-citrulline in each daily serving, in addition to other clinically backed nutrients, and is a high quality, third-party tested option for runners and endurance athletes who value effectiveness and convenience.
By promoting nitric production and enhancing blood flow, L-citrulline supports the cardiorespiratory system so that athletes can unlock the full potential of their endurance training.