L-Arginine
An amino acid that serves as a precursor to nitric oxide (NO), promoting vasodilation. Common in pre-workout products, though oral bioavailability is lower than citrulline.
An ingredient with still-limited research
Buy
(PR)The links below include affiliate links (PR).
Effects reported in research
May improve blood flow via nitric oxide production
May contribute to subjective pump sensation during training
Potential additive effect when combined with citrulline
Dosage & timing
- 3–6 g, 30–60 minutes before exercise.
- Citrulline may be a more effective alternative for NO production.
Cautions
- •High doses (10 g+) may cause GI discomfort (diarrhea, bloating).
- •Those with low blood pressure or on cardiovascular medications should consult a doctor.
Supporting research
Similar supplements
Agmatine
Confidence: LowAgmatine sulfate
A decarboxylation product of arginine. Under investigation for NOS modulation, neural effects, and insulin secretion, but human evidence remains limited.
Pre-Workout Supplement (Stimulant-Free)
Confidence: ModerateMulti-ingredient blend without caffeine: citrulline, beta-alanine, creatine, betaine, etc.
Pre-workout products without stimulants like caffeine. Suitable for evening training, caffeine-sensitive individuals, or those who want to avoid sleep disruption. Key active ingredients include citrulline and beta-alanine.
Beetroot (Dietary Nitrate)
Confidence: ModerateDietary Nitrate, Beetroot Extract
Dietary nitrate found abundantly in beetroot is reported to be converted in the body via nitrite to nitric oxide (NO), promoting vasodilation and improved oxygen utilization efficiency. Multiple studies have shown modest benefits for aerobic and endurance performance, including improvements in VO2max and time-trial completion. Effects tend to be more pronounced in recreational to intermediate-level athletes than in elite competitors.