Citrulline Malate Pre-Workout: Does It Work?


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May 13, 2016
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What is Citrulline Malate?​

Citrulline malate is made up of two compounds – citrulline and malate.

L-citrulline is an amino acid that takes its name from the latin word for watermelon. The malate part comes from malic acid, which comes from the latin word for apple – malic acid contributes to the tart taste of apples.

The story starts back in the late 1970’s, when researchers found 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 a popular ingredient in many pre-workout formulas, mainly on the basis that it helps to fight fatigue.

Much like creatine and beta-alanine, it’s popular mainly with people who want to boost their performance during high-intensity exercise.

And, unlike a lot of supplements out there, citrulline malate has got some research to back it up.

Citrulline Malate Pre-Workout: Does It Work?​

Back in 2010, researchers found that a group of trained men could do more reps on the bench press after being given a pre-workout drink containing 8 grams of citrulline malate 60 minutes before training [1].

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.

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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.

citrulline malate table

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.

In set 16, there was a 53% improvement, with the men able to grind out, on average, an extra two reps.

More interesting still, citrulline malate also led to a 40% decrease in muscle soreness when it was measured 24 and 48 hours after the workout.

A follow-up study, published in 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 [2]. 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.

There’s more:

In a group of female masters tennis players, taking 8 grams of citrulline malate 60 minutes before exercise improved both cycling power and maximal grip strength [3].

When a group of 15 women took 8 grams of citrulline malate an hour before lifting weights (6 sets of the bench press and leg press to failure), they could complete significantly more reps in both exercises [4]. What’s more, the women also reported lower overall feelings of exertion when taking citrulline malate.

In a similar study, a group of resistance-trained men performed three sets each of chin-ups, pull-ups, and push-ups to failure [5]. Taking 8 grams of citrulline malate before exercise led to a significant increase in the amount of reps performed for each exercise.

What’s more, the benefits have shown up with training protocols that involve both a large (15-16) and small (5) number of sets per muscle group, as well as short (60 seconds) and long (3 minutes) periods of rest between sets.

That’s the good news.

The bad news is that citrulline malate is not a magic bullet, and hasn’t been shown to work every time.

We have a handful of studies to show that citrulline malate has a positive effect on exercise performance. But there are almost as many to show that it works no better than a placebo.

In one trial, 12 grams of citrulline malate taken 60 minutes before exercise failed to improve cycling performance in a group of well-trained men [6].

In another, 6 grams of citrulline malate taken before a workout had no effect on post-exercise muscle soreness or various markers of muscle recovery [7].

Eight grams of citrulline malate taken 40 minutes before training had no effect on performance during 5 sets to failure on the bench press [8]. Nor did it have any positive effect on subjective measures of focus, energy or fatigue.

Citrulline malate did nothing for performance during a circuit comprising squats, lunge jumps, squat jumps and lateral jumps [9].

Citrulline malate also failed to improve subjects’ ability to resist fatigue during 10 sets of 10 reps on an isokinetic leg extension machine [10].

What’s more, post-exercise muscle soreness was higher in the citrulline malate group compared to those given a placebo.

Interestingly, when the researchers tested various citrulline malate supplements, they found that the ratio of citrulline to malate was not equivalent to the ratio stated by the manufacturer.

In fact, the supplement used in the study contained just over half the manufacturers stated dose of citrulline.

Even the studies that do show a positive effect of citrulline malate come with some important limitations.

First, 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, none of the research has 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 several months.

Most of the studies have used around 8 grams of citrulline malate.

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.

We don’t know if citrulline malate will deliver performance gains over and above what you might expect from those other ingredients.

Final Thoughts​

The research on citrulline malate is a bit of a mixed bag. While some studies show that it reduces fatigue, improves performance and lowers post-exercise muscle soreness, others show that it has no effect.

The inconsistent set of results may be down to the fact that not all citrulline malate supplements contain what they’re supposed to.

In fact, very few studies report whether the supplement being used contains the stated amount of citrulline malate. The ones showing no benefit may have used a supplement containing less citrulline malate than the manufacturers claim.

But even then, most of the trials have looked at changes in performance following a single dose of citrulline malate, rather than long-term changes in muscle size.

An increase in the number of reps with a given weight should, in theory at least, translate into bigger muscles over time. But there’s currently no research that draws a direct line between regular use of citrulline malate and a faster rate of muscle growth.

Some of the research on citrulline malate does point towards a measurable benefit. And the science behind it does makes sense, on paper at least.