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For a lot of people into fitness, pre-workout has become part of going to the gym. It is meant to help them feel more alert and push harder during exercise. But a new study suggests that the boost may come at the expense of sleep.
Researchers analyzing data from 912 Canadians ages 16 to 30 found that those who had used pre-workout supplements in the past year were 2.5 times as likely to report the shortest sleep durations. Compared with nonusers, they were 2.53 times as likely to say they averaged five hours of sleep or less a night, rather than eight hours, the study’s reference point.
More Workouts, Less Sleep
The paper, published in Sleep Epidemiology, examined participants in the Canadian Study of Adolescent Health Behaviors. About 22.2% reported using pre-workout supplements in the past 12 months. Sleep was already scarce across the sample: 34.9% averaged seven hours a night, 25% averaged six, and 10.6% reported sleeping five hours or less. Only 20.4% said they got eight hours.
Pre-workout supplements are designed to do the opposite of what bedtime asks of the body. They are typically sold as multi-ingredient products meant to sharpen exercise performance, and they often contain caffeine, creatine, nitrates, branched-chain amino acids, and sweeteners.
Their caffeine content can be especially high: the paper cites a range of 91 to 387 milligrams per serving, with an average of 254 milligrams. That’s roughly 2.5 cups of coffee, assuming about 100 milligrams in a 240-mL cup.
That amount is enough to plausibly disturb sleep. Caffeine blocks adenosine receptors, helping people feel alert instead of sleepy. It can also delay melatonin rhythms and activate the sympathetic nervous system, changes that may keep the body in a more wakeful state.
The strongest link was among the shortest sleepers. Even after taking into account age, gender, race, ethnicity, sexual orientation, education, symptoms of depression and anxiety, and recent weight training, the researchers found that young people who used pre-workout were more likely to report sleeping five hours or less a night. They did not find the same pattern for those sleeping six hours, seven hours, or nine hours or more.
That suggests a greater chance of falling into the shortest and most concerning sleep bracket.
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The timing of workouts may help explain why. Many young people exercise late in the day, after school, jobs, or commuting. In the discussion, the researchers cited a recent meta-analysis recommending that people take pre-workout supplements more than 13 hours before bedtime. That is rather unrealistic for someone training in the late afternoon or evening.
“Pre-workout supplements, which often contain high levels of caffeine and stimulant-like ingredients, have become increasingly popular among teenagers and young adults seeking to improve exercise performance and boost energy,” lead author Kyle T. Ganson, of the University of Toronto, said in a statement.
“However, the study’s findings point to potential risks to the well-being of young people who use these supplements.”
A Warning, Not a Final Verdict
Credit: Wikimedia Commons
The study does not prove that pre-workout directly causes short sleep. It was cross-sectional, meaning it captured a snapshot rather than following people over time. The authors note that the relationship could run both ways: some people may be sleeping too little first, then using pre-workout to compensate for fatigue.
The research also could not measure how much supplement people took, when they took it, or which formulations they used. The team recruited participants through social media instead of using a nationally representative sample, and they relied on participants to report their own sleep.
Even so, the findings raise a practical concern. A product sold to support training and performance may, if taken too late, undermine recovery itself.
The authors say health professionals should ask adolescents and young adults about pre-workout use and advise them to avoid these supplements 12 to 14 hours before bedtime.
