Pre-workout supplements can improve cardio performance, but the benefit comes almost entirely from one ingredient: caffeine. The other common ingredients in most pre-workout formulas, like citrulline and beta-alanine, have little to no proven effect on aerobic exercise. So whether a pre-workout is “good” for your cardio session depends on what’s in it, how much you take, and the type of cardio you’re doing.
Caffeine Is the Ingredient That Actually Works
Of everything in a typical pre-workout, caffeine has the strongest and most consistent evidence for improving endurance. The International Society of Sports Nutrition calls aerobic endurance the form of exercise with the “most consistent moderate-to-large benefits” from caffeine, though results vary between individuals. The effective dose is 3 to 6 mg per kilogram of body weight, taken about 60 minutes before exercise. For a 70 kg (155 lb) person, that’s roughly 210 to 420 mg, which lines up with what most pre-workout servings contain.
Caffeine helps cardio through several pathways at once. It increases the release of adrenaline, which ramps up fat mobilization so your body can tap into fat stores more efficiently at moderate intensities. It blocks adenosine receptors in the brain, which promotes the release of acetylcholine and dopamine. The practical result: you perceive less effort and fatigue during the same workload. Caffeine also increases motor unit recruitment (meaning your muscles contract more efficiently) and may improve muscle oxygen saturation during moderate-intensity exercise. All of these effects stack, which is why caffeine reliably improves time to exhaustion, pace, and overall endurance output.
One notable finding: caffeine increases maximal fat oxidation during graded exercise, meaning your body burns more fat at its peak fat-burning intensity. If you’re doing steady-state cardio partly for body composition, that’s a meaningful bonus.
Other Common Ingredients Fall Short
Most pre-workouts contain more than caffeine, and the marketing suggests those extras matter for performance. The research tells a different story for cardio specifically.
Citrulline malate is marketed as a blood flow enhancer that should, in theory, improve oxygen delivery during endurance work. A systematic review and meta-analysis of citrulline supplementation found no positive effects on aerobic performance, perceived exertion, VO2 kinetics, or lactate levels. The pooled data showed essentially zero effect on oxygen uptake. A few individual studies found small improvements in muscle oxygenation, but the overall picture is clear: citrulline doesn’t meaningfully improve cardio performance based on current evidence.
Beta-alanine is another staple ingredient, included to buffer acid buildup in muscles during high-intensity efforts. While it has some support for very short, maximal-effort bouts (like a single all-out sprint), a study on beta-alanine supplementation during high-intensity interval training found no improvement in repeated sprint ability, muscle buffering capacity, or neuromuscular fatigue. For most cardio sessions, whether steady-state or intervals, beta-alanine likely isn’t contributing much.
This doesn’t mean these ingredients are useless in all contexts, but if you’re paying a premium for a multi-ingredient formula and your primary goal is cardio, the extras aren’t pulling their weight.
Where Pre-Workout Helps Most
Not all cardio is the same, and the type of session matters. Caffeine-based pre-workout tends to shine brightest in longer, sustained efforts: a 5K run, a 45-minute cycling session, a long swim. These are the scenarios where delayed fatigue, lower perceived effort, and better fat utilization add up over time.
For shorter cardio sessions (a quick 20-minute jog, a light bike ride), you probably won’t notice much difference. The session is over before fatigue becomes a limiting factor. Caffeine also helps when you’re training in heat or at altitude, with doses of 3 to 6 mg/kg supported in both conditions. And if you’re exercising after a poor night’s sleep, caffeine can partially offset the cognitive and physical performance dip that comes with sleep deprivation.
Even simple alternatives to a full pre-workout supplement can deliver the same core benefit. Caffeinated chewing gum, energy gels, mouth rinses, and plain coffee have all been shown to improve aerobic performance. If you don’t want the tingling skin from beta-alanine or the extra cost of a branded supplement, a cup of strong coffee 30 to 60 minutes before your run does much of the same work.
Heart Rate and Blood Pressure Concerns
Cardio already elevates your heart rate and blood pressure, so layering stimulants on top deserves some attention. An integrative review of pre-workout supplements and cardiovascular health found that most studies (20 out of 24) did not find harmful changes in blood pressure, heart rate, or cardiac events. However, a meaningful minority of users do experience symptoms. In survey data from two of the reviewed studies, 11% to 23% of pre-workout users reported palpitations or accelerated heartbeat.
Short-term blood pressure increases have been documented. One study found that pre-workout raised both systolic and diastolic blood pressure acutely, though the effect disappeared after six weeks of regular use, suggesting the body adapts. The more serious cardiovascular events in the literature, including ischemic heart disease, arrhythmias, and cerebrovascular problems, were primarily associated with products containing synephrine, an ingredient chemically similar to the banned substance ephedrine. Synephrine combined with caffeine can trigger dangerous spikes in blood pressure and heart rate.
The practical takeaway: standard caffeine-based pre-workouts are well-tolerated by most people during cardio. But check the label for synephrine or other stimulant stacks, and pay attention to how your body responds during the first few uses. If you feel chest tightness, dizziness, or an unusually rapid heartbeat, back off the dose or switch to a simpler caffeine source.
Timing and Dosing for Cardio
Pre-workout supplements are designed to be taken 30 to 60 minutes before exercise. For caffeine specifically, 60 minutes is the most commonly studied timing, which allows blood levels to peak right as you start your session. If you’re using a caffeinated gel or gum, absorption is faster and you can take it closer to your start time.
Doses above 6 mg/kg don’t produce better results and come with a higher rate of side effects: jitteriness, nausea, elevated heart rate, and difficulty sleeping afterward. The minimum effective dose may be as low as 2 mg/kg (about 140 mg for a 70 kg person), so starting on the lower end and adjusting upward is a reasonable approach, especially for cardio where you want to feel energized without feeling wired.
If you do regular evening cardio, timing matters for sleep too. Caffeine’s half-life is roughly 5 to 6 hours, so a pre-workout taken at 6 PM means half the caffeine is still circulating at 11 PM. For late sessions, a stimulant-free pre-workout or simply skipping it altogether avoids trading better cardio performance today for worse recovery tonight.
The Bottom Line on Pre-Workout for Cardio
Pre-workout is good for cardio, but mostly because of caffeine. It reliably improves endurance, reduces how hard the effort feels, and helps your body burn fat more efficiently at moderate intensities. The other ingredients commonly found in pre-workout formulas, particularly citrulline and beta-alanine, don’t have strong evidence for aerobic performance. If your goal is better cardio sessions, a well-dosed caffeine source taken about an hour beforehand is the simplest, most evidence-backed approach. Everything else on the label is largely along for the ride.