What Does Pre-workout Do?

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    Pre-workout supplements can boost exercise performance, stamina, and muscle gains. They vary greatly, so be informed on how to choose.

    What is a pre-workout?

    If you are looking to get a leg up on fitness and power your workouts, then pre-workout supplements might be on your radar. Pre-workout supplements often have a range of ingredients that can give you energy and increased stamina during exercise, help you gain strength, and aid the exercise recovery process. While the outcomes may be desirable, you also want to be informed about potential side effects.

    Are pre-workout supplements effective?

    The effectiveness of pre-workout supplements greatly depends on the ingredients, which can vary widely among brands. How effective they are also depends on dosage, consistency of usage, your body type and your fitness goals.

    Are pre-workout supplements safe?

    When used properly and as directed, pre-workout supplements can be safe. However, high doses of caffeine often in these supplements can cause negative side effects in some people. In addition, some pre-workouts may contain ingredients that are not well studied. Be sure to choose supplements from reputable manufacturers that use high-quality ingredients and have their products third-party tested for purity to avoid potential contaminants or unknown substances.

    What does pre-workout do?

    Let’s go into further detail about what pre-workout can do.

    Increases energy and focus

    It’s a no-brainer that if pre-workouts contain caffeine (which most do), then they will boost your energy. Caffeine-containing products have been shown to enhance both aerobic and anaerobic performance.

    The branched chain amino acids (BCAAs) in most pre-workouts have been shown to help improve mental focus, allowing people to run harder and longer.

    Boosts strength and stamina

    Pre-workout supplements can help build strength through a variety of mechanisms. One main ingredient, creatine, provides energy to muscles and can increase strength and power output during exercise.

    Other ingredients commonly found in pre-workout supplements, such as beta-alanine, may help improve muscle endurance and reduce fatigue, enabling some to do more repetitions and sets of exercises. This increased workload can lead to greater gains in strength over time.

    Increases blood flow

    More blood flow means more oxygen to the muscles as well as more waste management, which means that the blood carries away waste created in the muscle to be excreted. These effects may help improve endurance. Caffeine can increase blood flow, which has been shown to positively correlate with increased performance recovery between periods of high-intensity exercise.

    Other common ingredients in some pre-workout supplements that can increase blood flow include the amino acids arginine and citrulline, which can help increase the production of nitric oxide, which can dilate blood vessels.

    Reduces soreness and delays fatigue

    The effect of increased blood flow from pre-workout ingredients also works to reduce fatigue and aid in muscle recovery. Additional substances in pre-workouts can reduce fatigue include beta-alanine, creatine, taurine, tyrosine, and caffeine. Soreness and fatigue onset typically occurs due to lactic acid buildup in the muscle during exercise. Beta-alanine in particular can help to delay that onset.

    How to take a pre workout

    Taking a pre-workout supplement properly is important for safety and effectiveness.

    Tips on taking a pre workout

    Before you start, carefully read the label to make sure you are taking the right dose and to understand the potential side effects. Always be informed before taking any supplement.

    Stay hydrated. Some ingredients in pre-workouts can lead to dehydration, so be sure to drink plenty of water before, during, and after exercise.

    When is it best to take pre workout?

    Pre-workout supplements are typically best taken 30-60 minutes prior to a workout to allow the ingredients to take effect. Avoid taking these supplements too close to bedtime since they may keep you awake. Therefore, it may be best to time exercise and pre-workout use for earlier in the day.

    Should you take pre-workout every day?

    Most pre-workout supplements can be taken daily for a period of time. In fact, daily use of creatine is best for saturating and maintaining muscle stores of creatine. However, it is a popular recommendation to cycle off pre-workout every few weeks to avoid becoming tolerant to the ingredients, although research to back this up is limited.

    How long does pre-workout take to kick in?

    In general, pre-workout supplements can take anywhere from 20 to 60 minutes to take effect. This is because the ingredients need time to be absorbed into the bloodstream and reach the target areas of the body.

    How long does pre workout last?

    The duration of time the supplements last depend on the specific ingredients in the supplement, your individual metabolism, and your sensitivity to stimulants. Some may have a short duration of action, while others may provide sustained energy for hours.

    How to choose a pre workout supplement that is best for you

    Since not all pre-workout supplements are the same, it is important to find one that’s right for you. Let’s walk through some of the key ingredients in most pre-workout supplements.

    Key ingredients to look for in a pre workout supplement

    Beta alanine

    One of the most popular pre-workout ingredients is beta-alanine. Beta-alanine is an amino acid that can help increase carnosine levels in the muscles. Carnosine is a compound that helps buffer lactic acid, which can build up in the muscles during intense exercise and contribute to fatigue. By increasing carnosine levels, beta-alanine may help delay the onset of muscle fatigue and allow individuals to perform more reps and sets of exercises.


    Caffeine boasts of several benefits when taken before exercise, including increased energy and alertness, improved endurance, reduced perceived exertion (making it easier to complete a workout), increased fat metabolism, and enhanced muscle contraction.

    One meta-analysis published in 2021 found that fairly small doses of about 0.9-2 mg/kg of caffeine appeared to be the minimum effect dose and had similar effects compared to studies using higher caffeine doses. For most people, that’s equivalent to approximately 1-2 cups of coffee.


    Creatine is an amino acid primarily stored in the skeletal muscles where it is used as an energy source during physical activity. It is naturally produced in the body but can also be taken as a supplement to boost levels in the muscles. Supplementing with creatine may help increase strength and power output during resistance training exercise. It may even help combat muscle loss related to aging when paired with regular strength training.

    In terms of how to take creatine, it is generally recommended to start with a loading phase to full saturate muscle stores, followed by a daily maintenance phase dose of 3-5 grams per day.


    Electrolytes are minerals that serve to produce an electric current throughout the body which facilitates nerve signaling, muscle contraction, and maintaining fluid balance in the body. To maintain exercise performance, adequate electrolytes in the body is required. Taking supplemental electrolytes or eating foods rich in electrolytes before or during exercise can help, especially since some electrolytes are lost in sweat. The significant electrolytes are sodium, potassium, and chloride, along with magnesium, calcium, phosphate, and bicarbonates.


    L-citrulline is an amino acid commonly included in pre-workout formulations that plays the role of increasing blood flow. Citrulline is converted into the amino acid arginine, which then converts to nitric oxide which can dilate blood vessels, allowing for improved blood flow to the muscles. By increasing blood flow to the muscles, citrulline may be able to improve endurance and reduce fatigue during exercise.

    Additionally, citrulline may also help increase the production of ATP (adenosine triphosphate) in the body. ATP is the primary source of energy for muscle contractions, and an increase in ATP production may help improve strength and power output during exercise.

    A carbohydrate source

    Pre-workout supplements may sometimes contain a carbohydrate source because carbohydrates can provide the body with a quick source of energy during exercise. These sources often include sugars listed as dextrose or maltodextrin which are rapidly absorbed by the body and can provide a quick source of energy for the muscles.

    However, it is important to note that the amount of carbohydrates in a pre-workout supplement should be balanced with the individual's exercise goals and dietary needs. Consuming too many carbohydrates before exercise can lead to a rapid spike in blood sugar levels, which can cause a subsequent crash in energy levels and may be detrimental to exercise performance.

    Overall, a carb source in a pre-workout can be helpful but should be tailored to one’s individual needs.


    B vitamins are essential for various metabolic functions in the body involved in energy production and therefore important to have in adequate amounts for exercise performance. The B vitamins B6, B12, and folate help convert the macronutrients (carbs, fats, and proteins) into energy to power the muscles and other parts of the body. This study found that exercise may increase the need for b vitamins in the body.

    It is important to note that the amount and types of B vitamins included in pre-workout supplements can vary greatly, and not all forms of b vitamins in pre-workouts are active. Be sure to look for B12 as methylcobalamin.

    Ingredients to avoid in a pre-workout supplement

    Be sure to check the ingredients list before buying your pre-workout supplement. It is best to avoid unnecessary fillers and additives including artificial food coloring or artificial flavors. Avoid excessively high doses of caffeine. Also be careful with proprietary blends that do not tell you how much of each ingredient is included.

    Potential risks and side effects of taking a pre workout

    Pre-workout supplements contain high amounts of caffeine, which can lead to symptoms such as increased heart rate, jitters, and anxiety. Consuming too much caffeine can also lead to dehydration and electrolyte imbalances, especially during intense exercise. Ingredients that increase blood flow can also cause headaches in some people.

    Tips to avoid the negative side effects of pre-workout

    Start with a low dose when first starting a pre-workout supplement, and gradually work your way up to the recommended dosage. This can help you determine your tolerance and avoid any negative side effects.

    If caffeine seems to be an issue for you, you can look for pre-workouts without caffeine, or add your own sources of caffeine, like matcha powder or a small amount of coffee, in order to manage the doses yourself.

    Be sure to drink plenty of water when taking pre-workout supplements to avoid dehydration.

    Who should take a pre-workout?

    Athletes or those who regularly engage in intense or prolonged exercise may benefit from pre-workout supplements, as they can provide a quick source of energy, enhance focus, and improve exercise endurance, strength and recovery.

    It is important to note, however, that while pre-workout supplements may be able to enhance strength gains, they should be used in conjunction with a proper diet and exercise program to see optimal results.

    Who shouldn't take a pre-workout?

    Pre-workout supplements are not necessary for everyone, and some individuals may not tolerate the ingredients well or may not need the additional supplementation.

    Individuals who are pregnant, nursing, or have pre-existing medical conditions should consult with a healthcare provider before taking a pre-workout supplement.

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    Dr. Carla Montrond Correia ND, CNS
    Medical Content Manager
    Dr. Montrond-Correia is a licensed naturopathic physician and a certified nutrition specialist (CNS). She holds degrees from University of Bridgeport, Georgetown University, and University of Saint Joseph, and supplemented her education with internships in the health and wellness space. She's focused on research, herbal medicine, nutrigenomics, and integrative and functional medicine. She makes time for exercise, artistic activities, and enjoying delicious food.
    Victoria Peck-Gray, RD
    Freelance Contributor
    Victoria is a registered dietitian and functional nutritionist who helps people with resistant weight loss and PCOS transform their metabolic health and lose weight through a functional nutrition and lifestyle approach that addresses root causes. She is owner of her private practice, Wonderfully Made Nutrition and also leads her group metabolic coaching program for women called The 4 Method.