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Pre-Workout: What Does It Really Do?

These caffeine-packed supplements can give your workouts a boost

Pre-workout supplements.

If you’re an athlete or a regular gym-goer, you’ve likely heard the buzz around pre-workout supplements. These products promise to boost energy and enhance workout performance.


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But before you gulp down a glass of pre-workout powder, it’s important to know what’s actually in this supplement and how it affects your body. Registered dietitian Kate Patton, MEd, RD, CCSD, LD, talks about what it is, what it can do and what to know before you try it.

What is pre-workout?

“Pre-workout supplements are pills or powders that are meant to be consumed about half an hour before exercising,” Patton says.

Each super-charged scoop or capsule acts like a turbo-boost to your system, thanks to a mix of vitamins and nutrients — plus a whole darn lot of caffeine.

What does pre-workout do?

Fans of pre-workouts say these concoctions give them extra energy to exercise and help them recover faster afterward.

But how? Patton walks you through the most common ingredients in pre-workout supplements and how they may help improve your performance.

  • Amino acids: There are 20 different kinds of these molecules, including beta-alanine, valine, isoleucine and leucine. “Amino acids grow and repair muscles, decrease muscle soreness and aid in energy production,” Patton explains.
  • Beta-alanine: This amino acid helps produce carnosine, which improves muscular endurance.
  • Caffeine: This common substance helps increase endurance for high-intensity exercise and can improve your focus and reaction time. “Pre-workouts’ promise of increased energy, focus and performance is usually made possible through a jolt of caffeine,” Patton notes.
  • Creatine: Popular among athletes, creatine supplies energy to your muscles. It can increase strength and improve your performance.
  • Glucose: Glucose is just another name for sugar, which is included in pre-workout supplements because it can increase your energy levels.
  • Nitric oxide: This compound, made of oxygen and nitrogen, increases your blood flow. “This may improve intense bursts of exercise, like when you’re doing sprints or weight-lifting,” Patton says. “It can also help reduce inflammation and enhance recovery.”
  • B vitamins: These vitamins play many roles in your body, but they’re especially helpful in converting food to energy and transporting nutrients through your body.


Benefits of pre-workout

The main ingredient in most pre-workout products is caffeine, which isn’t necessarily a bad thing. “Caffeine can be great in the appropriate amount,” Patton says.“It stimulates the body’s central nervous system, improves reaction time and can reduce fatigue.”

Taking a pre-workout can also:

  • Give you extra energy for your workout.
  • Improve your exercise performance.
  • Help you recover faster after working out.

Pre-workout side effects

Just because you can buy them over the counter doesn’t mean they’re 100% safe or without risk. For starters, pre-workouts contain anywhere from 150 milligrams (mg) to 300 mg of caffeine per serving, which can pack the same punch as chugging three cups of coffee in a row. Yikes!

Patton recommends choosing a product with 200 mg caffeine or less per serving. “It’s always wise to read the product label and proceed with caution,” she advises. “And if you’re sensitive to caffeine, pre-workouts are definitely not going to be a good choice for you.”

Even if you’re not typically sensitive to caffeine, the kind of buzz you get from pre-workout can still cause issues associated with over-caffeination, especially if you take more than the recommended amount or if you’ve already had a lot of caffeine beforehand. Side effects include:

  • A racing heartbeat.
  • Gastrointestinal issues, like diarrhea.
  • High blood pressure.
  • Tingling feelings in your arms and legs.
  • Nausea.

And importantly, beware of “dry-scooping,” an incredibly dangerous practice popularized on social media. This perilous TikTok trend involves downing a scoop of dry pre-workout powder without mixing it into water. It can cause choking or aspiration, which can lead to aspiration pneumonia. “And that amount of caffeine all at once can cause irregular heartbeat, palpitations and even heart attack,” Patton warns.

Is it safe to use every day?

Pre-workout makes for a quick boost on days when you’re feeling extra sluggish. “These products can be beneficial and safe to take if the ingredients are correctly listed on the label and the company is credible,” Patton says.

If you work out a lot, though, you probably shouldn’t take pre-workout more than once a day, and always be sure to carefully follow dosage instructions.

And remember: You can’t out-supplement a bad diet. The best way to get energy for your workout is by eating healthy foods that are rich in vitamins and nutrients.

“Many of the safe, natural ingredients typically found in pre-workouts can be obtained through eating real food instead,” Patton states. Before you hit the gym, go for:

  • Coffee.
  • Whole-grain sandwich with lean protein.
  • Turkey.
  • Yogurt.
  • Cheese.
  • Eggs.
  • Beets, celery or leafy greens.


“You don’t always know what ingredients are packaged into your pre-workout supplements,” Patton says, “but with whole foods, you always know what you’re getting.”

Take a deeper look at some typical pre-workout ingredients, what they do and how to get them naturally in your diet:

Learn more about our editorial process.

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