Most pre-workout supplements are considered safe for many adults, but they are not essential for health or exercise performance. Their ingredient mixes vary widely by brand. Ingredients like caffeine, ...

While there’s no single definition of what a pre-workout supplement should contain, many include various combinations of caffeine, beta-alanine, creatine, nitrates, and branched-chain amino acids ...

C4 Pre-Workout is a workout supplement line from Cellucor that people may take before exercise to help increase energy, alertness, and strength. They contain caffeine and creatine, which may help ...