Performance-enhancing supplements are food-derived compounds taken to improve exercise capacity, increase strength or endurance, or speed up recovery. Unlike banned drugs, the most effective options work by topping off your body’s natural energy stores, buffering acid buildup in muscles, or improving blood flow and oxygen delivery during hard efforts. A handful have strong research behind them, while the vast majority sold in stores do not.
How Supplements Enhance Performance
Performance supplements work through a few core mechanisms. Some act as stimulants on the nervous system, making you feel more alert and delaying fatigue. Others increase the stored fuel available for intense muscle contractions. A third group helps neutralize the metabolic byproducts (like hydrogen ions) that build up during hard exercise and force you to slow down. And some simply provide raw material for repairing muscle tissue after training.
Not every supplement on the shelf does what the label claims. The ones below have consistent evidence from multiple studies showing measurable effects on performance in specific contexts.
Creatine: Short-Term Power and Strength
Creatine monohydrate is the most studied performance supplement in existence. Your muscles store a compound called phosphocreatine, which acts as an emergency energy reserve during explosive efforts like sprinting, jumping, or heavy lifts. When your muscles burn through their primary fuel (ATP), phosphocreatine donates a phosphate group to regenerate it almost instantly. Supplementing with creatine increases those phosphocreatine stores, giving you a few extra seconds of peak output before fatigue sets in.
The practical result is the ability to squeeze out one or two more reps, recover slightly faster between sets, and sustain repeated bursts of high-intensity effort. Over weeks of training, those small gains compound into measurably greater strength and muscle growth. The standard approach is 3 to 5 grams per day, taken consistently. Older protocols called for a “loading phase” of about 20 grams per day for five to seven days, but research shows continuous daily intake at the lower dose reaches the same muscle saturation levels over time. Loading just gets you there faster.
Caffeine: Endurance and Alertness
Caffeine improves performance primarily by stimulating the central nervous system, reducing your perception of effort and delaying the point where exercise feels unbearable. It has consistently been shown to help at doses of 3 to 6 milligrams per kilogram of body weight. For a 70-kilogram (154-pound) person, that translates to roughly 210 to 420 milligrams, or about two to four cups of coffee.
Doses as low as 2 mg/kg may still provide a benefit, while going above 9 mg/kg increases side effects like jitteriness, nausea, and a racing heart without adding further performance gains. The most common recommendation is to consume caffeine about 60 minutes before exercise, since blood levels peak around that time. Caffeine tends to help endurance activities like distance running and sports with sustained intermittent effort (soccer, basketball) more than pure short-burst efforts like a single heavy deadlift or a 100-meter sprint.
Beta-Alanine: Buffering Muscle Burn
Beta-alanine is the building block your body needs to produce carnosine, a compound stored in muscle fibers that acts as a buffer against acid buildup. During intense exercise lasting one to four minutes (think 400- to 800-meter runs, rowing intervals, or high-rep sets), hydrogen ions accumulate and interfere with muscle contraction, producing that familiar burning sensation. Higher carnosine levels help soak up those ions and delay the point where your muscles give out.
Supplementing with 2 to 6 grams per day has been shown to raise muscle carnosine concentrations by 20 to 80 percent over four or more weeks. The effect builds gradually, so unlike caffeine, you won’t notice anything from a single dose. One common side effect is a harmless tingling sensation on the skin (paresthesia), which is why many people split their daily dose into smaller portions of 800 milligrams to a gram taken throughout the day.
Citrulline: Blood Flow and Oxygen Delivery
Citrulline is an amino acid that your body converts into arginine, which then drives the production of nitric oxide, a molecule that relaxes blood vessel walls. Wider blood vessels mean more blood and oxygen reaching working muscles during exercise and more efficient removal of waste products. It’s a roundabout route, but supplementing with citrulline actually raises blood arginine levels more effectively than taking arginine directly, because arginine is largely broken down in the gut before reaching the bloodstream.
The most commonly studied form is citrulline malate (citrulline paired with malic acid), typically taken as a single 8-gram dose before training. Results across studies have been mixed, with some showing clear benefits for resistance exercise and cycling performance and others showing little effect. The inconsistency may come down to differences in dosing timing, training status of the participants, and the type of exercise tested.
Sodium Bicarbonate: High-Intensity Acid Buffer
Sodium bicarbonate (ordinary baking soda) works on the same problem as beta-alanine, acid buildup, but from the outside of the muscle cell rather than the inside. It increases the blood’s buffering capacity, helping pull hydrogen ions out of working muscles faster. This is most useful for high-intensity efforts lasting roughly one to seven minutes.
The effective dose is 0.2 to 0.3 grams per kilogram of body weight, taken 60 to 180 minutes before exercise. For a 70-kilogram person, that’s about 14 to 21 grams. Higher doses don’t add performance benefits and come with a well-known downside: gastrointestinal distress, including bloating, cramping, and nausea. Individual tolerance varies widely, so anyone interested in trying it should experiment well before any competition.
Protein for Recovery
Protein supplements aren’t performance enhancers in the traditional sense. They don’t make you stronger during a workout. But they directly supply the amino acids your muscles need to repair and grow after training, which is the foundation of long-term performance improvement. Whey protein is the most studied form. Research in resistance-trained young men (around 80 kilograms) found that 20 grams of whey protein after a workout stimulated muscle protein rebuilding by about 49 percent above baseline. Bumping the dose to 40 grams only added a small additional increase (56 percent), suggesting 20 grams is the practical ceiling per serving for most people. Larger or older individuals may benefit from slightly higher amounts.
What Doesn’t Hold Up
For every supplement with solid evidence, there are dozens marketed on hype. Arginine, despite its role in nitric oxide production, has repeatedly failed to show meaningful performance benefits when taken as a direct supplement, either alone or combined with branched-chain amino acids. A review of 54 clinical studies concluded it provided little to no enhancement of athletic performance or recovery. This is precisely why citrulline (which raises arginine levels indirectly) became the preferred option.
Multi-ingredient pre-workout blends present a different problem. Most research has tested individual compounds in isolation, so the effects and safety of the specific combinations found in commercial products are largely unknown. A product containing five or six ingredients at various doses hasn’t necessarily been studied as that particular mix.
Supplement Quality and Contamination
One of the biggest risks with supplements isn’t the listed ingredients but what’s not on the label. Products can contain unlisted stimulants, hormones, or compounds that appear on the World Anti-Doping Agency’s prohibited list. The 2025 WADA prohibited list includes substances like tesofensine (a stimulant increasingly appearing on supplement labels) and MOTSc (an experimental peptide marketed for weight loss through wellness clinics and social media). Neither is approved for human therapeutic use.
If you’re a competitive athlete subject to drug testing, third-party certification is critical. The U.S. Anti-Doping Agency recognizes NSF Certified for Sport as the program best suited for reducing the risk of a contaminated product. NSF tests for prohibited substances and verifies that what’s on the label matches what’s in the bottle. Even if you’re not a tested athlete, choosing certified products is a straightforward way to avoid supplements spiked with undisclosed ingredients that could pose health risks.
Choosing Supplements for Your Goals
The right supplement depends entirely on the type of exercise you do. Creatine is best suited for activities built on repeated short bursts of power: weightlifting, sprinting, and team sports with frequent accelerations. Caffeine has the broadest application but shines most in endurance events. Beta-alanine and sodium bicarbonate both target the “muscle burn” zone of sustained high-intensity work, with beta-alanine requiring weeks of daily use and sodium bicarbonate working acutely before a single session. Citrulline may benefit both resistance training and endurance work through improved blood flow, though the evidence is less consistent.
Stacking multiple supplements is common practice, but the research supporting specific combinations is thin. The safest approach is to introduce one supplement at a time, assess whether it makes a noticeable difference over several weeks, and only then consider adding another. This also makes it easier to identify which supplement is responsible if you experience side effects like GI discomfort, jitteriness, or skin tingling.