Broadly speaking, citrulline malate is an “anti-fatigue” supplement.
Much like creatine and beta-alanine, it’s popular mainly with people who want to boost their performance during high-intensity exercise.
The supplement itself has been used for a lot longer than people think.
In fact, studies going back to the 1970’s show that citrulline malate, in the form of a product called Stimol, helps to reduce both mental and physical fatigue in geriatric and post-surgery patients.
Stimol has also been shown to improve muscle performance in subjects suffering from asthenia, a condition which describes the loss or lack of body strength.
In recent years, citrulline malate has become popular as a way to boost performance during intense exercise.
And, unlike a lot of supplements out there, citrulline malate has got some research to back it up.
Back in 2010, researchers found that a group of trained men were able to do more reps on the bench press after being given a pre-workout drink containing 8 grams of citrulline malate 60 minutes before training .
A group of 41 men from Spain took part in the study. Each man took part in two testing sessions with a 7-day gap between each one. Here’s what each testing session involved:
Bench Press 4 sets
Incline Bench Press 4 sets
Incline Flyes 4 sets
Bench Press 4 sets
Each subject received either citrulline malate or a placebo the first time around, and then the one they didn’t get during the second test.
The number of reps performed in each set of the bench press was recorded. The results for each set are shown in the table below.
As you can see, citrulline malate did improve performance, with the benefits showing up mainly towards the end of the workout.
In the fourth set, for example, citrulline malate led to a 17.5% gain, with the average number of reps performed going from 6 to 7.05.
But in set 16, there was a 53% improvement, with the men able to grind out, on average, an extra two reps.
A follow-up study, published in the March 2015 issue of the Journal of Strength and Conditioning Research, shows very similar results.
This time, a group of 12 men trained their legs on two separate occasions . Both workouts involved five sets to failure on the leg press, hack squat and leg extension.
Each subject received either 8 grams of citrulline malate or a placebo 60 minutes before the first workout, and the one they didn’t get before the second workout.
When they were given citrulline malate before training, the men performed a significantly higher number of repetitions. On average, the supplement improved performance by a total of 9% across all three exercises.
If you do plan to spend your money on citrulline malate, there are a few things worth considering.
First of all, both studies involved a relatively high volume of training, with 15-16 sets per muscle group, and weights in the 60-80% of 1-RM range.
If you’re following a program that involves a lower training volume, heavier weights and longer inter-set rest periods (such as one of the 5×5 workouts), chances are you’re not going to see the same results.
The authors of the Spanish study acknowledge as much, writing that:
“It is likely that citrulline malate supplementation would be less effective in enhancing the performance of anaerobic sessions with sufficient rest time or high enough intensity, where lower levels of acidosis, lactate, and ammonium production would occur.”
We don’t know if citrulline malate’s effect on exercise performance will persist over time. In other words, is it still going to work as well if you’ve been using it for several weeks? Or will the effects gradually decline after regular use?
In addition, neither study looked at changes in muscle mass over time. It remains to be seen if citrulline malate has any impact on muscle growth when it’s used consistently for a 2-3 month period.
As I mentioned earlier, the researchers used 8 grams of citrulline malate, or roughly 0.1 grams per kilogram of bodyweight.
It’s possible that you might get the same results with a lower dose. But we don’t know for sure, as research looking at the effect of lower doses on exercise performance in trained individuals has yet to be published.
Keep in mind that many pre-workout products won’t contain anywhere near 8 grams of citrulline malate.
Very few supplements list the precise amount of citrulline malate they contain, preferring instead to include it in their “proprietary blend” of ingredients. This lets them hide the fact that their formula contains very little of the active ingredients listed on the bottle.
What’s more, most pre-workout formulas contain a bunch of other ingredients besides citrulline malate, including creatine, caffeine, beta-alanine and so on. This study doesn’t tell us whether citrulline will deliver performance gains over and above what you might expect from those other ingredients.
There may also be side effects associated with citrulline malate, with 15% of subjects in the Spanish study reporting a feeling of “stomach discomfort” after taking citrulline. No side effects were reported in the follow-up trial.
If you’re the experimental type, and assuming that your training program and diet are in order, citrulline malate does merit a place on your “worth a try” list. If you want to use it, go for a bulk citrulline malate powder so you can make sure you’re getting the right amount.
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ABOUT CHRISTIAN FINNChristian Finn holds a master's degree with distinction in exercise science, is a certified personal trainer and has been featured on BBC TV and radio, as well as in Men's Health, Men's Fitness, Fit Pro, Zest, and Perfect Body magazine.
1. Pérez-Guisado J, Jakeman PM. (2010). Citrulline malate enhances athletic anaerobic performance and relieves muscle soreness. Journal of Strength and Conditioning Research, 24, 1215-1222
2. Wax B, Kavazis AN, Weldon K, Sperlak J. (2015). Effects of supplemental citrulline malate ingestion during repeated bouts of lower-body exercise in advanced weightlifters. Journal of Strength and Conditioning Research, 29, 786-792