What is Nitric Oxide and Why Does It Matter?
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Nitric oxide (NO) is a gas that dilates blood vessels. More NO = better blood flow to muscles.
NO effects on training:
- Better muscle pump
- More oxygen to muscles
- Better endurance
- Faster recovery
Arginine - The Original NO Booster
L-arginine is an amino acid from which the body directly produces nitric oxide.
Logic: More arginine → more NO → better pump
Problem: Arginine absorbs poorly and breaks down in the intestines.
Arginine Studies
Studies have been disappointing:
- Highly variable absorption (20-50%)
- Digestive issues at high doses
- Unclear results for athletic performance
Citrulline - The Better Alternative
Citrulline is an amino acid that's converted to arginine in the body, then to NO.
But why does citrulline work better than direct arginine?
The Citrulline Bypass
- Arginine is broken down in intestines by enzymes
- Citrulline bypasses this breakdown
- Citrulline converts to arginine in kidneys
- This arginine reaches bloodstream cleanly
Result: Citrulline raises blood arginine more than arginine itself (Schwedhelm et al., 2008)!
Scientific Comparison
Arginine
| Property | Result |
|---|---|
| Absorption | 20-50% |
| NO increase | Moderate |
| On digestion | Harsh (diarrhea) |
| Performance improvement | Unclear |
| Dose | 6-10g |
Citrulline
| Property | Result |
|---|---|
| Absorption | 80%+ |
| NO increase | Significant |
| On digestion | Gentle |
| Performance improvement | Proven |
| Dose | 6-8g (as citrulline malate) |
Citrulline Forms
L-Citrulline
- Pure citrulline
- Dose: 3-5g
- Best for: General NO support
Citrulline Malate (2:1)
- Citrulline + malic acid
- Dose: 6-8g (= ~4-5g citrulline)
- Best for: Training performance, endurance
- Bonus: Malate supports energy production
Citrulline Malate (1:1)
- Half citrulline, half malate
- Dose: 8-10g needed for same effect
- Lower quality products
Citrulline Studies
Strength Training (2010)
Study: 41 men, bench press to failure (Pérez-Guisado & Jakeman, 2010)
Result with 8g citrulline malate:
- +52% more reps compared to placebo
- Less muscle soreness 24-48h after
Endurance (2016)
Study: Cyclists, 4km time trial (Bailey et al., 2015)
Result with 6g citrulline:
- -1.5% time (significant in competitive sports)
- Better oxygen utilization
When to Take?
Citrulline
- 30-60 minutes before training
- 6-8g citrulline malate
- Empty stomach or with light meal
Daily use:
- Can take on rest days too
- 3-6g L-citrulline
- Helps maintain NO levels
Arginine
If you use at all:
- Smaller doses (3-5g)
- Split into multiple doses
- Don't expect big effect
Who Should Take Citrulline?
Greatest benefit:
- Strength trainers (better pump, more reps)
- Endurance athletes (better oxygen delivery)
- High-intensity trainers
- Those wanting better pump
Less benefit:
- Low-intensity trainers
- Beginners (baseline sufficient)
Combinations
Good Combination
Citrulline + beta-alanine + caffeine
- Classic pre-workout combination
- Each component supports different aspect
Citrulline + creatine supplements
- Pump + strength
- Complementary mechanisms
Avoid
Citrulline + arginine
- Same pathway, don't need both
- Citrulline alone is sufficient
Our Recommendation
Choose citrulline, not arginine!
- Dose: 6-8g citrulline malate (2:1) before workout
- Timing: 30-60 min before training
- Frequency: On training days
- Form: Powder (cheaper) or in pre-workout
Forget arginine - it's an outdated supplement that citrulline replaces in every aspect.
Summary
| Question | Answer |
|---|---|
| Which is more effective? | Citrulline |
| Which absorbs better? | Citrulline |
| Which is gentler on digestion? | Citrulline |
| Which to buy? | Citrulline |
Citrulline is one of the few pre-workout supplements that actually works. Arginine is a historical relic.
Browse our citrulline selection at MaxFit.ee →
References
- Pérez-Guisado J, Jakeman PM. (2010). Citrulline malate enhances athletic anaerobic performance and relieves muscle soreness. Journal of Strength and Conditioning Research, 24(5), 1215-1222.
- Bailey SJ, Blackwell JR, Lord T, et al. (2015). L-citrulline supplementation improves O2 uptake kinetics and high-intensity exercise performance in humans. Journal of Applied Physiology, 119(4), 385-395.
- Schwedhelm E, Maas R, Freese R, et al. (2008). Pharmacokinetic and pharmacodynamic properties of oral L-citrulline and L-arginine. British Journal of Clinical Pharmacology, 65(1), 51-59.
- Gonzalez AM, Trexler ET. (2020). Effects of citrulline supplementation on exercise performance in humans: A review of the current literature. Journal of Strength and Conditioning Research, 34(5), 1480-1495.
- Bescós R, Sureda A, Tur JA, Pons A. (2012). The effect of nitric-oxide-related supplements on human performance. Sports Medicine, 42(2), 99-117.
See also:
- Citrulline Malate: The Science of Muscle Pump and Performance Enhancement
- Best Pre-Workout Supplements 2026: Complete Ranking
- Beta-Alanine: Complete Guide for Athletes
