Pre-workout supplements marketed for energy and performance may be sabotaging sleep for teens and young adults. A new study found users were more than twice as likely to report dangerously short sleep—likely due to the products’ heavy doses of caffeine and stimulants. Credit: Shutterstock A new analysis from the Canadian Study of Adolescent Behaviors suggests that teenagers and young adults who take pre-workout dietary supplements, including products like Bang!, Jack3D, and C4, are far more