Bodybuilding legend Arnold Schwarzenegger is taking a hard look at two popular pre-workout supplements. In an Arnold’s Pump Club newsletter shared on Dec. 10, 2025, he weighed the performance boost impact offered by L-arginine and citrulline malate.
As a seven-time Mr. Olympia champion, Arnold Schwarzenegger was after any edge he could get onstage. For many athletes today, pre-workout formulas have become a go-to. Some are caffeinated, whereas others are simply focused on maximizing pump.
Pre-workout supplements can be a fantastic tool. Users often include them before exercise to aid endurance, strength, and power. Below, Schwarzenegger examines whether these substances fall short of their promised claims.
Arnold Schwarzenegger Discusses Whether Common Pre-Workout Ingredients Are Actually Helping Your Workouts
In the newsletter, Schwarzenegger examined a new controlled study that saw participants use L-arginine and citrulline malate.
“Do These Two Pre-Workout Ingredients Do Anything? This New Study Put It to the Test
If you’ve ever taken a scoop of pre-workout and wondered, “Is this helping…or is it just making my face tingle?” — you’re not alone. Supplements promise more reps, more power, and better endurance. But a new controlled study took a hard look at two popular ingredients (L-arginine and citrulline malate) to see if they deliver when it counts.”
Though they are popular options, Schwarzenegger noted that the study found no performance boosts concerning CrossFit, cardio, or cycling sprints.
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“The surprising finding: despite their popularity, l-arginine and citrulline malate didn’t improve performance in CrossFit, cardio, or cycling sprints.”
Looking at 46 individuals, there were no differences in heart rate, rounds completed, or performance.
“Researchers recruited 46 healthy, trained participants and put them through three challenging workouts — a Wingate cycling sprint, the CrossFit “Cindy” workout, and the Harvard Step Test — after giving them either a placebo or a combination of L-arginine and citrulline malate (common nitric-oxide–boosting ingredients found in many pre-workouts).
There was no difference in rounds completed, heart rate, or overall performance between the CrossFit workouts. For the Harvard Step Test, there was also no difference in cardio fitness or recovery. And on the Wingate sprints, no boost in peak or average power.”
Schwarzenegger believes the lack of benefits could have been due to the goals tested.
“Why didn’t the supplements work? The authors believe there are a few possible explanations. For one, they just might not be effective for the goals tested. While citrulline and l-arginine are designed to increase blood flow, other studies have been inconclusive about how much they improve performance.”
Additionally, he shared that nitric-oxide boosting supplements can take longer to work and are often more effective with consistent use.
“It’s also popular that the ingredients may take longer to work. Nitric-oxide–boosting supplements might be more effective with regular, chronic use rather than short-term use for individual hard workouts. Other studies have suggested that the combination of arginine and citrulline could help with repeated-sprint performance, workouts that require more volume (think higher reps), and reducing the perceived effort of a workout.”
While he admits they can help with the pump, Schwarzenegger isn’t sold on their performance payoff just yet.
“If you’re buying arginine or citrulline hoping for an instant performance boost, this study suggests you may not notice any real difference. Your pump might feel good, but the performance payoff might not be there.”
This wasn’t Schwarzenegger’s first time scrutinizing supplements. He recently called out a ‘very disturbing’ fact about pre-workouts, noting that in one study, 89% of supplements didn’t contain the ingredients they promised on the label.
Even in retirement, Schwarzenegger doesn’t miss a chance to examine the latest fitness research. When it comes to arginine or citrulline, he’s unsure if they are actually providing substantial benefits.