L-citrulline is often associated with the “pump” in weight training. However, its benefits extend beyond short, intense workouts. For endurance activities, it may play a key role in reducing fatigue. Let’s take a look at how it works and what you can actually expect.

Understanding L-citrulline and its role in the body

An amino acid central to nitric oxide production

L-citrulline occurs naturally in the body as an amino acid.  Once absorbed, L-citrulline is converted into L-arginine, which contributes to the production of nitric oxide (NO). This nitric oxide promotes vasodilation, that is, the widening of blood vessels.

In practical terms, this means better blood circulation. And better circulation means better transport of oxygen and nutrients to the working muscles.

Why is blood circulation essential during prolonged physical activity?

In endurance sports, fatigue isn’t caused solely by a lack of energy; it’s also linked to theaccumulation of metabolites, such as ammonia, and reduced muscle oxygenation.

Improved blood circulation can therefore help to:

• Improve oxygen delivery to the muscles;

• Facilitate the elimination of certain metabolic waste products;

• Support energy production at the cellular level.

That is why L-citrulline is attracting growing interest for prolonged physical activity.

L-citrulline and muscle fatigue: What mechanisms are at play?

When we talk about fatigue, we need to distinguish between several aspects: peripheral muscle fatigue, central fatigue, and the sensation of increased exertion. L-citrulline primarily acts on peripheral mechanisms, but its effects can influence the overall perception of exertion.

A potential reduction in ammonia buildup

During prolonged physical exertion, energy metabolism produces ammonia. At high concentrations, this molecule is associated with feelings of fatigue and decreased performance.

L-citrulline plays a role in the urea cycle, the process thatcontributes to the elimination of ammonia. By supporting this mechanism, it may limit the accumulation of this metabolic waste product.

This can result in a feeling of “lighter” legs and the ability to maintain intensity for longer.

Improved energy efficiency

Thanks to its role in the production of nitric oxide, L-citrulline improves blood flow. Better muscle perfusion means a more consistent supply of oxygen.

However, oxygen is essential for ATP production through aerobic pathways. During long-duration exercise, where aerobic metabolism predominates, this optimization can make all the difference.

We’re not talking about a dramatic improvement, but in the context of structured training, every small improvement can make a difference.

A possible impact on the perception of effort

Some evidence suggests that L-citrulline may reduce the subjective perception of exertion. Again, this doesn’t mean that the effort becomes easy, but that you can tolerate it for longer.

Whether it's a half-marathon, a bike ride lasting several hours, or a long game, this difference in how you feel can influence your strategy and your consistency.

What are the concrete benefits for endurance sports?

Improved muscular endurance

In certain situations, supplementation with L-citrulline, which is found in our energy powder and our energy nasal spray is associated with an improved ability to sustain repeated exertion or maintain a given intensity.

For long-duration activities, this can mean:

• Greater stability in power or pace;

• A reduction in the decline in performance toward the end of the test;

• Faster recovery between back-to-back sessions.

Easier recovery

Fatigue doesn't stop when the workout ends; it continues into the recovery phase. Improved blood circulation can help deliver nutrients and remove waste products after exercise.

This can help reduce muscle soreness and support muscle recovery. For those of you who are stringing together long workouts, this is far from a minor consideration.

An interest in combined strategies

L-citrulline can be incorporated into a more comprehensive approach: hydration management, carbohydrate intake during exercise, and targeted supplements for focus or energy, as we’ve discussed on Sniffy.

How should L-citrulline be used for endurance activities?

When to take it

L-citrulline is generally taken before exerciseto support nitric oxide production when you need it.

For prolonged exercise, taking it 30 to 60 minutes before the start is often recommended. Some protocols may include regular intake during periods of intensive training.

Of course, we recommend that youtailor any supplementation to your profile, your activity level, and, if necessary, to seek advice from a healthcare professional.

A personalized approach to energy

Everyone reacts differently. Some will notice a clear improvement in exercise tolerance, while others will experience a more subtle effect.

That is why we encourage you to test it gradually, paying attention to how you feel, your recovery, and your ability to maintain the intensity.

If you're looking to maximize your endurance while exploring innovative ways to boost your energy and focus, you can also check out our other products, such as our energy gummies. They are part of a modern approach, designed to meet the specific needs of today’s active individuals and athletes.

By combiningstructured training, quality recovery, and appropriate supplements, you’ll give yourself the best possible chance of managing fatigue more effectively over the long term.