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Pre-workout supplements, or “pre-workouts,” are one of the most popular types of fitness supplements. Both serious athletes and recreational gym-goers take them.

Pre-workouts are designed to increase your physical and mental energy during workouts.

The effects of a pre-workout will last anywhere from 30 minutes to 2 hours after you consume the supplement. Of course, this varies depending on the ingredients, the particular effects you’re interested in, and other factors.

This article breaks down everything you need to know about pre-workout supplements, including effects, duration, benefits, risks, and tips to consider if you choose to take a pre-workout.

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Pre-workout supplements are a category of dietary supplements designed to enhance your workout through increased energy, work capacity, and focus and potential performance improvements.

They’re meant to increase the “pump,” or blood flow to and from your muscles, with ingredients that dilate your blood vessels, such as arginine. They also contain caffeine, which can help increase your energy levels.

Additionally, the creatine in some pre-workout supplements may increase your performance during high intensity tasks.

Most pre-workouts come in powder form, and you mix them with water or juice. Some pre-workouts are sold as capsules or canned or bottled drinks.

There are many pre-workout supplements available from a variety of brands, and each supplement has a different formula.

Many pre-workouts list each ingredient, including the dose per serving. Some pre-workouts list only a proprietary blend of ingredients but not the individual amount of each.

Here are the most common ingredients in typical pre-workout supplements, according to research (1):

  • beta-alanine
  • caffeine
  • citrulline
  • tyrosine
  • taurine
  • creatine
  • niacin, also known as vitamin B3
  • arginine

The defining feature of most pre-workout supplements is the combination of some or all of these ingredients.

In addition to these substances, many manufacturers add flavoring, coloring, and artificial sweeteners to improve the taste and appearance of the dissolved product.

Summary

Pre-workouts are a type of supplement. They contain various ingredients to improve aspects of performance during workouts. Common ingredients include caffeine, arginine, and creatine.

Pre-workouts contain several ingredients with effects that last varying lengths of time.

Two of the top studied active ingredients in pre-workouts are caffeine and arginine.

With most pre-workouts, it will take 60–90 minutes for these two ingredients to kick in. The maximum effects appear 60 minutes after consumption for caffeine and 60–90 minutes after consumption for arginine (2).

Arginine in pre-workouts causes the blood vessels to widen, increasing blood flow. Research suggests the half-life of arginine is anywhere from 30–120 minutes, depending on the dose and the individual (3, 4).

Caffeine has a longer half-life of around 5 hours. Research suggests the acute effects of caffeine kick in fully after 1 hour and can last anywhere from 1.5–9.5 hours, depending on the individual (5).

Given the varying half-lives of caffeine and arginine, the effects of a pre-workout will last anywhere from 30 minutes to 2 hours.

Since the research shows a range of half-lives for the relevant ingredients across individuals, your experience with the onset and duration of pre-workout effects may vary.

The exact duration of pre-workout effects ultimately depends on:

  • the amount of each ingredient per serving
  • the number of servings you consume in a particular period of time
  • your body mass
  • your activity level
  • your sensitivity to caffeine
Summary

Most pre-workout effects last at least 2 hours. This varies by ingredient. For example, the increased blood flow from arginine may wear off in 1–2 hours, while the energy boost you may get from caffeine can take 6 hours or more to wear off.

Multi-ingredient pre-workouts appear to be relatively safe (6).

However, pre-workouts contain multiple ingredients that can potentially be harmful if you consume them in excess.

Here are some potential risks of pre-workouts.

Caffeine toxicity

Caffeine can be harmful and even fatal when consumed in excess. When consuming caffeine in a traditional way, such as by drinking coffee or tea, it’s difficult to reach a fatal dose due to the volume of liquid you would need to consume.

However, consuming concentrated powders like pre-workouts that contain high doses of caffeine makes it far easier to consume massive amounts. Thus, these products pose a greater risk than caffeinated drinks.

Individuals who consume multiple caffeinated beverages in addition to pre-workouts may be at risk of a caffeine overdose. People with lower body weights may be more at risk.

One 2019 study looked at consumption habits and negative effects of pre-workouts. Most people surveyed said they took one serving with each use, but 14% took two or more servings. Eighteen percent said they took pre-workouts more than once per day (7).

In the same study, 54% of people who consumed pre-workout supplements reported the following side effects (7):

  • skin reactions
  • heart abnormalities
  • nausea

Females were more likely to experience these side effects, as were people who consumed two or more servings of pre-workout per day.

The heart abnormalities and nausea are associated with the high caffeine intake, while niacin causes flushing in the skin. The magnitude of these effects increases with the dose.

One review of studies in humans found that fatal doses of caffeine tended to be 5 grams or more but were as low as 3 grams in some cases (8).

Pre-workouts tend to contain 250–400 mg of caffeine per serving (7).

To reach a 3-gram dose of caffeine with a pre-workout that contained a high dose of 400 mg of caffeine per serving, you would have to consume only 7.5 servings of pre-workout.

While this is quite a bit more pre-workout than most people would consume, it’s easily possible for a person to take this much in a day. That’s why it’s important to moderate your intake.

Niacin toxicity

At high doses, niacin can cause serious reactions, including (9):

  • dangerously low blood pressure
  • liver damage that can result in liver failure
  • multiple organ failure

Research suggests liver damage happens at niacin doses of around 3 grams per day (9).

Taking much lower doses of niacin — around 30 mg per day — can induce a harmless but uncomfortable condition called niacin flush (9).

This condition causes your skin to become red and itchy and feel warm. It normally goes away within about an hour (9).

Some of the top pre-workout supplements contain 25.8 mg of niacin on average and may contain up to about 41 mg. Thus, it’s possible you might experience niacin flush after taking one serving of pre-workout (1).

To know how much niacin you’re actually taking, check the amount per serving listed on the label of the product, and make sure to take the recommended serving size.

Other safety concerns

Scientists have not studied the long-term safety of taking pre-workout supplements, so it’s not known whether these supplements have harmful long-term effects.

Furthermore, additional ingredients may have different side effects or may increase the side effects of caffeine. That’s why it’s difficult to generalize about the safety of all pre-workout supplements.

Some supplements may even contain banned or harmful ingredients. That’s because, in the United States, pre-workouts are not regulated by the Food and Drug Administration (FDA).

Supplement manufacturers in the United States don’t have to test ingredients for safety before adding them to a product. Unless an ingredient is specifically banned or forbidden, companies can add it to dietary supplements with little oversight.

Additionally, as long as companies don’t claim that a supplement treats, cures, or prevents a specific illness, they can make any claims they want about the effectiveness of the product.

Thus, it’s really a case of “buyer beware” with pre-workouts and other supplements.

May contain substances banned in professional sports

Banned substances may be a safety issue. Additionally, if you compete in a sport that requires testing for performance-enhancing drugs, it’s important to know that taking some pre-workout products may get you disqualified.

In the past, athletes have tested positive for banned substances after ingesting trace amounts when they took supplements that purported to contain unrelated ingredients.

For example, a study in 2013 found the banned stimulant N,α-diethyl-phenylethylamine (N,α-DEPEA), a methamphetamine analog, in a pre-workout supplement called Craze (10).

In this relatively high profile example, several athletes were disqualified from competition after testing positive for the banned stimulant, ultimately resulting in the analysis and detection of this substance in the pre-workout formula.

A 2020 analysis of 17 supplement brands found several banned substances in various amounts and combinations in the different supplements (11).

Among the substances detected in this analysis were the following prohibited stimulants:

  • deterenol
  • phenpromethamine
  • beta-methylethylamine
  • octodrine

The presence of these banned substances in pre-workout supplements is worrisome, and it’s difficult to say whether the inclusion of these ingredients was intentional or accidental.

Even more concerning is the lack of data around the short- and long-term effects of combining multiple stimulants in varying amounts that aren’t disclosed on the label.

Although these substances are banned, U.S. supplement companies are not legally required to publish test results for these substances, and it’s up to the consumer to ensure a pre-workout supplement has been third-party tested.

These substances have unknown health consequences and, at the very least, can lead to a serious hassle in the short term as coaches and athletes try to prove that a positive drug test was unintentional and caused by tainted supplements.

If you’re a competitive athlete, consider going the extra mile to ensure you get a pre-workout product that has been tested by a third party.

Safety guidelines

If you choose to take a pre-workout supplement, here are a few ways to make it safer:

  • Don’t consume more than a single serving per day.
  • Avoid consuming other supplements containing caffeine or niacin if you plan to take a pre-workout the same day.
  • Look for products that have been tested by a third-party organization, such as Labdoor or Eurofins Scientific.
  • Make sure every ingredient is listed, including the exact amount per serving.
  • Research each ingredient to verify what it is and find out any possible side effects or risks.
  • Avoid pre-workouts with so-called proprietary blends that don’t specify how many grams of each ingredient a single serving contains.
  • Always stick to a single dose of whatever pre-workout you take — half a dose if you’re on the smaller side. This is especially important when you’re trying a pre-workout formula for the first time.
  • If you’re taking medication or have any medical conditions, talk with a doctor about whether a pre-workout is safe for you. It may be helpful to show them the ingredients list of the specific pre-workout you’re interested in.
Summary

Most pre-workouts appear to be safe, but taking more than one dose per day may have side effects or pose health risks from some ingredients. If you choose to take one, stick to one serving and choose a product that’s third-party verified.

Companies that make pre-workouts most often market them to bodybuilders, powerlifters, and other weightlifting enthusiasts. Athletes in other sports may also take them.

In particular, caffeine provides proven benefits for both athletic and mental performance, although these benefits decrease as your tolerance to caffeine goes up over time.

Endurance, strength, and physique athletes can all potentially benefit from taking a pre-workout. However, many of the ingredients aside from caffeine are primarily targeted at activities related to weightlifting.

As long as you take proper precautions, pre-workouts can be appropriate for most high intensity sports, particularly if you’re resistance training or doing other weightlifting and maximal exertion activities.

Summary

Pre-workout supplements are mostly meant for high intensity training, such as weightlifting, but may benefit other athletes as well.

Safety concerns and exaggerated marketing aside, pre-workout supplements do have potential benefits for focus and performance at the gym.

How effective pre-workout supplements are largely depends on the specific aspect of performance you’re looking at.

For example, one study found that taking a caffeine-containing pre-workout supplement significantly increased anaerobic peak power and mean power (12).

It measured these with the Wingate Anaerobic Power Test, a common assessment of ability to exert intense effort over shorter time periods (12).

However, the same study found that taking a pre-workout did not boost upper body maximal strength or upper or lower maximal explosive power, as measured by bench press 1-repetition maximum, medicine ball put, and vertical jump tests (12).

Another review on the effectiveness of pre-workout supplements suggests they may help (6):

  • improve muscular endurance
  • improve mood
  • build lean muscle (when used while resistance training)

Pre-workouts have potential to improve various aspects of physical performance. But overall, research on the possible benefits of pre-workout supplements is inconclusive and more research is needed.

Summary

Some research has found that pre-workouts may help improve certain performance measures, particularly anaerobic power output.

If you’re interested in trying out a pre-workout, the following are some quality supplements from reputable brands. These supplements have all tested free of banned substances.

Always be sure to do your own research and consult a healthcare professional before trying these or other pre-workout supplements.

Transparent Labs Bulk

Transparent Labs Bulk pre-workout formula has roughly 180 mg of caffeine per serving, along with some beneficial vitamins.

The relatively simple formula does not have many unfamiliar ingredients and is a good introduction to the world of pre-workout supplements. It’s also free from artificial sweeteners, flavors, and colors.

Shop for Transparent Labs Bulk online.

Kaged Muscle Pre-Kaged

Pre-Kaged contains high levels of caffeine, B vitamins, and branched-chain amino acids.

The addition of creatine makes this an excellent choice if you perform anaerobic sports or lift weights, and it provides a serious energy boost due to the caffeine and B vitamins.

Shop for Kaged Muscle Pre-Kaged online.

Legion Pulse Pre Workout

Legion Pulse has about 350 mg of caffeine per serving, which puts it at the higher end of the range of caffeine content.

It also includes a number of other ingredients — such as L-theanine, citrulline malate, and beta-alanine — that are purported to have various beneficial effects for working out and training.

Additionally, Legion Pulse is naturally sweetened and flavored.

Shop for Legion Pulse pre-workout online.

Powher Pre-Workout for Women

Powher Pre-Workout is a low caffeine pre-workout supplement marketed to women. The formula contains a variety of plant extract additives that you should look into for yourself before taking it.

The overall caffeine content is at the lower end of the range at roughly 100 mg per serving, so this is a good choice if you are more sensitive to caffeine.

Shop for Powher pre-workout supplements online.

Performix SST Pre-Workout

Performix SST Pre-Workout is a high caffeine supplement with citrulline malate, lion’s mane, and yohimbe bark extract. These plant extracts combined with citrulline malate are purported to increase your blood flow and focus during workouts.

The high 300-mg dose of caffeine is the main driver in this pre-workout. As with all pre-workouts, make sure you moderate your overall caffeine intake and learn about the plant extracts before you take it.

Shop for Performix SSET pre-workout online.

Summary

Some reputable brands provide quality pre-workout supplements that have been verified by third-party testing. Always be sure to do your own research and consult a healthcare professional before trying these products.

Pre-workout supplements are a popular product and one of the most widely consumed dietary supplements. Many people use them, including fitness enthusiasts and professional athletes.

Most are designed to increase energy and performance during training and working out, and research does suggest they may benefit exercise performance, particularly for anaerobic power.

The biggest safety concern with pre-workouts is the high amount of caffeine they contain. You can lower this risk by sticking to a single serving per day and avoiding other caffeinated beverages during the same period.

Because the FDA doesn’t regulate supplements, pre-workouts may not contain what the label says they do, and they could be contaminated with banned or otherwise unsafe substances.

Consider buying a pre-workout supplement that a third party has tested for quality.