pre-workout

"Pre-workout" is a category of multi-ingredient dietary supplement taken before exercise; this product's main active ingredients are caffeine (a stimulant) and beta-alanine (an amino acid present in foods such as meat, poultry, and fish, and in supplements). The NIH Office of Dietary Supplements (ODS) notes that performance supplements like these often contain several ingredients in varied combinations, and that because most of those combinations have not been studied, their effectiveness and safety as a blend are not well established.

Evidence differs by ingredient and is not uniform. For caffeine, NIH ODS reports it may help improve endurance, strength, and power when taken before exercise, while noting that responses vary between individuals and that it does not help everyone. For beta-alanine, the picture is mixed: NIH ODS cites the International Society of Sports Nutrition's conclusion that beta-alanine (about 4-6 g/day taken for at least 2-4 weeks) may improve high-intensity exercise performance lasting longer than 60 seconds, with more modest benefits in efforts beyond about 4 minutes; but ODS also notes that other studies found no such benefit and that sports-medicine experts disagree on its value. NCCIH is more cautious, stating that studies of beta-alanine are "mixed but generally don't show that it improves athletic performance significantly." ODS further cautions that multi-ingredient pre-workout blends have not been adequately tested in combination, so a finished product's overall effect is uncertain.

These doses describe individual ingredients studied in research, not a specific product's formula. Per NIH ODS, caffeine doses studied for performance are roughly 2-6 mg per kg of body weight (about 210-420 mg for a 154-lb/70-kg person), typically taken 15-60 minutes before exercise; taking more is unlikely to improve performance further and raises the risk of side effects. Beta-alanine has been studied at about 4-6 g/day for at least 2-4 weeks, often split into smaller divided doses (commonly 2 g or less each, with meals) or taken as a sustained-release form to reduce tingling. Because pre-workout products combine stimulants with other actives and per-serving amounts vary widely (and proprietary blends may not list each amount), talk to a clinician or pharmacist before starting.

NIH ODS notes that performance supplements can have side effects and may interact with prescription and over-the-counter medications, and that many of these products contain multiple ingredients that have not been adequately tested together. Both ODS and NCCIH warn that some products marketed for bodybuilding or performance have been found to contain hidden or unlawful ingredients, including prescription drugs, controlled substances, and anabolic steroids; NCCIH adds that bodybuilding products are the most common cause of supplement-related liver injury and that liver injury from such products has risen in recent years. NCCIH also states that products containing the stimulants DMAA or BMPEA can cause serious health problems (ODS notes DMAA is among the ingredients FDA prohibits). People who are pregnant or breastfeeding, who have heart conditions or high blood pressure, who are sensitive to caffeine, or who are under 18 should consult a clinician before use.

Per NIH ODS, caffeine can cause insomnia and disturbed sleep, restlessness and nervousness, irritability and anxiety, nausea (and at higher exposure, vomiting), and a faster or irregular heartbeat, with higher doses (around 500 mg/day or more) raising the risk of these effects and potentially reducing rather than improving performance. The main reported side effect of beta-alanine is paresthesia, a tingling, prickling, or burning sensation (typically in the face, neck, hands, and upper trunk) that ODS describes as moderate to severe at doses of about 800 mg or more but not painful, serious, or harmful, usually lasting 60-90 minutes; using smaller divided doses or a sustained-release form can reduce it.

NIH ODS notes that cimetidine (Tagamet HB, used for duodenal ulcers) can slow the body's removal of caffeine and thereby increase the risk of caffeine-related side effects. ODS also cautions that combining caffeine with other stimulants can increase the potential for adverse effects, and that these performance supplements more broadly can interact with prescription and over-the-counter medications, so anyone taking other medicines or supplements should review the product with a clinician or pharmacist.