This article is part of a MensFitness.com series on the side effects of pre-workout supplements. We tapped Lonnie Lowery, Ph.D., R.D., associate professor of exercise physiology and nutrition at the University of Mount Union in Ohio and co-host of the Iron Radio podcast to help determine what exactly is causing the most uncomfortable offenses. To read more about the series, check out the first post here. Stay tuned for posts later this week explaining other strange pre-workout side effects!
Why Does My Pre-Workout Keep Me From Sleeping Hours Later?
Pre-workout supplements are loaded with caffeine to give you the energy to power through a workout. We all know caffeine itself will keep you awake, but it also activates epinephrine and norepinephrine—those fight or flight hormones—which will keep you wired as they course through your body. The half life of caffeine (how long it lasts) is typically three to five hours, but there's a genetic difference among the population with how quickly people metabolize it. Pretty much everyone will have trouble sleeping if they take a caffeine-heavy pre-workout supplement before an evening workout. But if you’re slow at metabolizing it, you don’t clear it out of your system as quickly and even ingesting it at lunchtime could affect your sleep.