L-Citrulline for Muscle: Does It Really Work?

study PMID: 40470618

Quick Summary: This research looked at whether taking L-Citrulline or L-Citrulline DL-malate helps men lift more weight. The study found that neither supplement improved performance compared to a placebo (a sugar pill).

What The Research Found

The study found that taking L-Citrulline or L-Citrulline DL-malate didn't significantly improve weightlifting performance in men. Both supplements were compared to a placebo. The study looked at how much weight the men could lift, how hard they felt they were working, and some blood markers. The results showed no real difference between the supplement groups and the placebo group.

Study Details

Who was studied: 36 men who regularly lift weights.

How long: 6 weeks.

What they took:

L-Citrulline
L-Citrulline DL-malate
Placebo (a sugar pill)

What This Means For You

If you're a weightlifter, this study suggests that taking L-Citrulline or L-Citrulline DL-malate might not give you a boost in the gym. It's important to remember that this study only looked at men who already lift weights. More research is needed to see if it might help other groups of people.

Study Limitations

The study only included men.

The study was relatively short (6 weeks).

The study only looked at certain measures of performance.

Key Findings

This study found no significant differences in resistance training performance, perceived exertion, or blood biomarkers between L-Citrulline (LC) and L-Citrulline DL-malate (CM) supplementation in resistance-trained men. Both groups showed comparable improvements in training volume (e.g., bench press, leg press) versus placebo, but these gains were not statistically distinct from placebo (p > 0.05). No meaningful changes occurred in blood lactate, ammonia, or creatine kinase levels. The primary conclusion was that neither LC nor CM provided ergogenic benefits beyond placebo after 6 weeks of supplementation.

Study Design

This was a randomized, double-blind, placebo-controlled trial with a parallel-group design. It included 36 resistance-trained men (mean age: 24.3 ± 3.1 years; training experience: ≥2 years) randomized into three groups: LC (n=12), CM (n=12), or placebo (n=12). Participants underwent supervised resistance training 3x/week for 6 weeks, with performance tests (e.g., 10-repetition maximum for upper/lower body) and blood draws at baseline and post-intervention.

Dosage & Administration

LC group: 8 g/day of pure L-Citrulline (free-form).
CM group: 8 g/day of L-Citrulline DL-malate (providing ~6 g L-Citrulline + 2 g malate).
Placebo: 8 g/day of maltodextrin.
Supplements were consumed 30 minutes pre-workout daily. Compliance was verified via capsule counts (>95%).

Results & Efficacy

Training volume: All groups increased total weekly volume (e.g., LC: +12.1%, CM: +10.8%, placebo: +11.5%), but no intergroup differences were significant (p = 0.78).
Perceived exertion (RPE): No differences in session RPE between groups (p = 0.32).
Blood biomarkers: Lactate, ammonia, and creatine kinase remained unchanged post-exercise across groups (all p > 0.05; 95% CIs overlapped zero).
Statistical power: The study was powered to detect a 10% performance difference (80% power, α=0.05), but observed effect sizes were trivial (Cohen’s d < 0.2).

Limitations

Small sample size (n=12/group) limited detection of subtle effects.
Homogeneous cohort: Only young, experienced male lifters were studied; results may not generalize to women, novices, or older adults.
Dose timing: Pre-workout administration only; effects of chronic daily dosing (non-training days) were unexamined.
Biomarker scope: Limited to acute post-exercise measures; long-term physiological adaptations were not assessed.
Placebo composition: Maltodextrin may not fully mask taste differences, risking unblinding.

Clinical Relevance

For resistance-trained individuals, neither L-Citrulline nor Citrulline Malate appears superior to placebo for enhancing training performance, recovery, or biomarkers over 6 weeks at 8 g/day pre-workout. Users should not expect meaningful ergogenic benefits based on this evidence. Future research should explore higher doses, longer durations, or diverse populations (e.g., untrained individuals). Current data suggest these supplements may not justify routine use for resistance training outcomes in experienced athletes.