A non-essential amino acid. Citrulline is involved in the urea cycle and is naturally found in certain foods and the body. It has gained popularity in the fitness and bodybuilding community due to its potential benefits. Here's a breakdown of how citrulline is often associated with bodybuilding:

1. **Nitric Oxide Production:**
Citrulline is converted into another amino acid called arginine, which is a precursor to nitric oxide (NO). Nitric oxide is a vasodilator, meaning it helps relax blood vessels, leading to increased blood flow. Enhanced blood flow can potentially improve nutrient and oxygen delivery to muscles during exercise, promoting better performance and recovery.

2. **Muscle Fatigue Delay:**
Citrulline is also believed to help reduce muscle fatigue by aiding in the elimination of ammonia, a byproduct of protein metabolism that can contribute to muscle fatigue. By reducing ammonia levels, citrulline may contribute to prolonged exercise endurance.

3. **Improved ATP Production:**
Some studies suggest that citrulline supplementation may increase adenosine triphosphate (ATP) production, which is the primary energy currency of cells. This could potentially contribute to better energy levels during workouts.

4. **Arginine Levels:**
Unlike arginine, citrulline is not as readily broken down in the liver, leading to higher and more sustained levels of arginine in the blood when citrulline is consumed. This may have implications for nitric oxide production.

5. **Potential Muscle Protein Synthesis:**
There is some research indicating that citrulline might play a role in promoting muscle protein synthesis, which is essential for muscle growth and recovery.

6. **Pre-Workout Supplementation:**
Citrulline is often included in pre-workout supplements to support increased blood flow, nutrient delivery, and overall workout performance.

It's important to note that while citrulline supplementation may offer benefits, individual responses can vary. As with any supplement, it's advisable to consult with a healthcare professional or a registered dietitian before incorporating it into your routine, especially if you have pre-existing health conditions or are taking medications.

Also, keep in mind that supplements should complement a well-balanced diet and a structured workout routine. There is no substitute for a comprehensive approach to fitness that includes proper nutrition, adequate rest, and consistent training.