Pre-workout supplements can improve running performance, but the benefit depends heavily on what’s in the formula, what distance you’re running, and how your body handles stimulants. The most reliable ingredient for runners is caffeine, which has been shown to improve endurance by 2 to 4% across dozens of studies. Other common pre-workout ingredients have weaker or more situational evidence behind them.
Caffeine Is the Most Proven Ingredient for Runners
Of everything packed into a typical pre-workout, caffeine has the strongest and most consistent evidence for endurance exercise. The International Society of Sports Nutrition identifies aerobic endurance as the form of exercise with the most consistent moderate-to-large benefits from caffeine use. The effective dose is 3 to 6 milligrams per kilogram of body weight. For a 150-pound (68 kg) runner, that works out to roughly 200 to 400 mg of caffeine, or about two to four cups of coffee.
One study found that 5 mg/kg of caffeine improved 5K race times by about 1% in both recreational and well-trained runners. That might sound small, but for a 25-minute 5K, it’s roughly 15 seconds. For longer efforts, the gains can be more noticeable: one treadmill study found a 12.5% increase in time to exhaustion at a moderate intensity, along with improved feelings of energy and focus. Caffeine also works in heat and at altitude, making it useful across a range of running conditions.
That said, not every pre-workout with caffeine will automatically help. A study on recreationally trained athletes found no significant difference in 5K race time between a multi-ingredient pre-workout supplement and a placebo. The supplement group averaged 23.62 minutes versus 23.51 for the placebo group. This suggests that the blend of ingredients matters, and simply having caffeine on the label doesn’t guarantee a performance boost.
How Beta-Alanine Works for Hard Efforts
Beta-alanine is one of the most common ingredients in pre-workout formulas, and it has a specific role: buffering the acid that builds up in your muscles during high-intensity effort. When you’re running hard, your muscles produce hydrogen ions that lower the pH inside muscle cells, contributing to that burning, heavy-legged feeling. Beta-alanine increases levels of a compound called carnosine in your muscles, which absorbs those hydrogen ions and delays the pH drop.
Beyond buffering acid, carnosine also helps your muscles stay sensitive to calcium signals that trigger contraction. As fatigue sets in and calcium release starts to decline, higher carnosine levels can help maintain force production a bit longer. This is why beta-alanine tends to show the most benefit during efforts lasting one to four minutes, like fast 800-meter repeats, tempo intervals, or race finishes where you’re pushing into a hard kick. For easy or moderate-paced runs, it’s unlikely to make a meaningful difference.
One important caveat: beta-alanine works through accumulation over weeks of daily supplementation, not from a single dose. Taking it only on run days as part of a pre-workout won’t build carnosine levels high enough to matter.
Citrulline Malate: Popular but Uncertain
Citrulline malate appears in many pre-workout formulas with claims about increasing blood flow and oxygen delivery. The theory is that citrulline converts to arginine in the body, which then boosts nitric oxide production and widens blood vessels. In practice, the evidence for runners is thin. Research has found that an 8-gram dose of citrulline malate had no measurable effect on muscle blood flow or oxygen consumption during exercise. A critical review of the ingredient concluded that enhanced blood flow doesn’t appear to be the mechanism behind whatever benefits have been observed, and the physiologically optimal dose remains unclear.
If your pre-workout contains citrulline, it’s unlikely to hurt, but it’s also not a reason to choose one product over another for running specifically.
Caffeine Won’t Dehydrate You Mid-Run
One of the most persistent concerns about caffeinated pre-workouts and running is dehydration. Caffeine does have a mild diuretic effect at rest, but a meta-analysis published in the Journal of Science and Medicine in Sport found that this effect essentially disappears during exercise. At rest, the diuretic effect was moderate. During exercise, it dropped to trivial, with no statistical significance. The researchers attributed this to the body’s natural anti-diuretic response during physical activity, which overrides caffeine’s mild effect on urine production.
The conclusion was direct: concerns about fluid loss from caffeine are unwarranted when ingestion happens before exercise. This holds true even during prolonged exercise in hot climates.
Stomach Problems Are a Real Risk
Runners are already prone to gastrointestinal issues. A survey of long-distance runners found that 26.1% reported GI symptoms during races, with bloating (18.6%), urgency to defecate (17.8%), and stomach pain (16.5%) being the most common complaints. Energy drinks were significantly associated with bloating during races, and eating or drinking anything within 30 minutes of starting was linked to increased bloating, urgency, and flatulence.
Pre-workouts often contain large doses of multiple ingredients, artificial sweeteners, and sometimes magnesium or sodium bicarbonate, all of which can irritate the gut, especially when your blood is being redirected away from your digestive system and toward your legs. If you’ve never used a pre-workout before running, test it on a low-stakes training day first, not before a race.
Timing and Practical Considerations
Most pre-workouts are designed to be taken 30 to 45 minutes before exercise, which aligns with how long caffeine takes to reach peak levels in your bloodstream. If you take it too close to your run, you may start before the caffeine kicks in, or worse, trigger stomach discomfort as your body tries to digest and absorb the ingredients while you’re already moving.
For early morning runners, a pre-workout can serve double duty as a caffeine source when you don’t have time or appetite for coffee and a meal. For afternoon or evening runners, be mindful that caffeine has a half-life of roughly five hours, so a 5 p.m. dose will still be active at 10 p.m.
When Pre-Workout Helps Most
Pre-workout supplements offer the clearest benefits for shorter, harder running efforts: 5Ks, interval sessions, tempo runs, and race-pace workouts where you’re operating near your limit. The combination of caffeine’s effect on perceived effort and beta-alanine’s buffering capacity aligns well with the demands of high-intensity running.
For easy runs and long slow distance, a pre-workout is largely unnecessary. The intensity isn’t high enough to benefit from acid buffering, and the caffeine boost matters less when you’re running at a conversational pace. You’re better off focusing on adequate sleep, hydration, and fueling.
If you want the performance benefits without the proprietary blends and filler ingredients common in pre-workout products, you can take caffeine and beta-alanine as standalone supplements in known doses. A cup or two of strong coffee provides 100 to 200 mg of caffeine, and 3 to 6 grams of beta-alanine daily (taken consistently, not just pre-run) will build muscle carnosine levels over several weeks. This approach gives you more control over exactly what you’re consuming and in what quantity.