The Preworkout Ingredient Glossary



A pre-workout supplement is anything that you take 30-60 minutes prior to a workout in an effort to increase your energy levels, provide more focus, improve athletic performance or all three. There are literally thousands of pre-workouts available so which one is best for a fitness enthusiast? Well, that depends on several factors including your fitness goals, willingness to take caffeine, preference on natural vs. artificial ingredients, and your body’s reaction to certain ingredients. The amount of energy you get from a pre-workout revolves around your history with caffeine.

“If someone has never taken a pre-workout supplement, they may feel jittery and too amped up,” says Jenevieve Roper, Ph. D, CSCS, CISSN and Assistant Professor of Health and Human Sciences at Loyola Marymount University. “If someone has taken preworkout previously or they take a lot of caffeine, it may not have the same negative effects.

It’s important to start slow and steady with pre-workouts, opting for formulas with low doses then increasing the dose if you’re reacting well to it. The absolute first step in figuring which product to try first (or next) is to ask yourself why you’re seeking out a supplement in the first place. Anne L’Heureux, RD, LD, SGX and owner of is an elite obstacle course racer who has tried several pre-workouts. She emphasizes the importance of doing research before just choosing a product.

“One of the traps people fall into is that they read an article about taking a certain pre-workout and they don’t ask themselves the question, ‘Is this individualized for my goal?’” says L’Heureux. “If I’m looking for more a strength and lean muscle outcome, that would come from protein powder or creatine. If someone is trying to improve their endurance/running, protein isn’t going to benefit them as much compared to a healthy carbohydrate and a bit of fat.”

The reason there are so many products is because there are so many combinations of ingredients. Once you find your ideal pre-workout, your athletic/fitness career can see a significant change–the ingredients in these products have been studied to work. A 2013 American Journal of Health System Pharmacy review of pre-workout effectiveness concluded, “Although evidence exists to support the performance-enhancement efficacy of some pre-workout ingredients as standalone agents, published data on combination products are scant, inconclusive, or conflicting.” While it’s not feasible to find research about every pre-workout available, knowing which ingredients are effective will help you pick the right one.

Take a look at what the experts say about popular pre-workout ingredients.

Caffeine (trimethylxanthine)

Caffeine is a central nervous stimulant that blocks adenosine receptors which is where adenosine binds to it. Adenosine is a natural chemical that serves many functions including helping our bodies feel tired when it binds to its receptor. Instead of adenosine, the adenosine receptor accepts caffeine disabling the sleepy effect of adenosine. As a result of this stimulant action, caffeine ingestion produces greater recruitment of motor units (a motor neuron and the muscle fiber it activates which may result in increases in strength and hypertrophy in response to lifting weights.

“Studies have shown the rate of perceived exertion in people that are taking caffeine is less,” says L’Heureux. “Two people can be doing the same workout but the person who took caffeine has a lower rate of perceived exertion. People often drink caffeine for energy but the workout itself may feel easier which I think is worth a try.”

As for dosges, L’Heureux suggest starting with 50mg for a few workouts and gauging how you feel. Then, L’Heureux says you can increase to 100mg of caffeine per workout.

“If caffeine is new for you, be aware of where you heart rate normally is during your workout,” L’Heureux says. “f your heart rate is higher than it normally would be after taking caffeine, then remove or decrease the caffeine. When you start taking caffeine and it affects your sleep, that has a more negative effect on your training.”


Creatine is a natural compound synthesized in the kidneys, pancreas, and liver. Once produced, creatine is released into the bloodstream and then mainly captured by muscles and the brain. In order to be usable for energy, creatine is converted to phosphocreatine by creatine kinase. Then phosphocreatine aids in the conversion of ADP to ATP, which is essential during both endurance and strength training.

“Creatine is one of the surefire supplements that the research has repeatedly supported for increasing muscle mass and strength,” Roper says. “Something bodybuilders should be aware of is that the gains you see may be mostly water because the more creatine you have in your system, the more water the body retains.”

Roper also mentions that the latest research suggests that caffeine and creatine should be taken at different times in the day due the effect on absorption.

“The research is conflicting but right now from what we can tell, consuming caffeine and creatine together kind of negatives the effect of creatine because the body doesn’t absorb the creatine the same way,” says Roper. “We’re waiting on more research but there have been several studies that have noted that consuming caffeine and creatine results in creatine not working the same way.”

“Creatine can be taken throughout the day but wait 1-2 hours after taking caffeine to take creatine although this depends on the person’s metabolism,” Roper adds.

L’Heureux agrees on the effectiveness of creatine for exercise performance.

“The review of creatine research has shown creatine has the ability to amplify the effects of resistance training, to improve the quality of high intensity intermittent speed training, to produce positive effects on fat-free mass and most recently has been studied for positive effects on endurance athletes,” says L’Heureux. “Creatine is the well-rounded supplement for the well-rounded athlete that need both strength and endurance such as an obstacle course racer.


Carbohydrate is one of the three macronutrients our bodies use for energy with the other two being fat and protein. Carbs are broken down into glucose into the body which is used for various process from brain function to digestive health. Once we start working out, our bodies burn through carbs first, regardless of the workout. For endurance athletes, eating more carbs means the body can store more glycogen (the stored version of glucose) and use that stored energy to go further during a workout.

“Consume carbs 30-60 minutes prior to an endurance workout and even the night before,” says Roper. “Try a mixture of complex and simple carbs so something like oatmeal and strawberries, blueberries or watermelon before a workout, but not necessarily a banana. Bananas do better post-workout. Typically, the higher water content a fruit has, the better because that water helps with breakdown in the stomach.

L’Heureux doesn’t advocate for endurance athletes undergoing no-carb diets.

“Merely based on the amount of time a runner, triathlete, or obstacle racer spends on the course, your body is going to be using up carbohydrates,” says L’Heureux. “Carbs can’t be completely eliminated because they provide antioxidants, minerals, and vitamins that are important for a strong immune system. When you’re training for 2-3 hours, you’re taxing your immune system and without adequate replenishment you’re at risk of getting sick.”


Electrolytes are electrically charged particles that control fluid balance in our bodies. L’Heureux says that the main four electrolytes that prevent cramping and dehydration during endurance events are sodium, potassium, magnesium and calcium. But don’t just wait until race day to take these electrolytes.

“What many people do is drink a heck of a lot of water a few days before the event but what they’re doing is flushing the body of electrolytes that the body needs for nerve impulses,” L’Heureux says. “What many people do is drink a heck of a lot of water a few days before the event but what they’re doing is flushing the body of electrolytes that the body needs for nerve impulses. Make sure you’re getting those through your food then 3-4 days prior to the event, replace a percentage of water intake with an electrolyte supplement depending on what you like (tablet, liquid, etc).”

Three or four days out from your endurance event, replace 25% of your water with electrolytes, the next day 50%, the next day 75%. The day before your event, 75% of your water should have electrolytes mixed in, L’Heureux says.

HMB (beta-hydroxy-beta-methylbutyrate)

HMB is a metabolite of the amino acid leucine that has been shown to be “effective in preventing exercise-related muscle damage in healthy trained and untrained individuals as well as muscle loss during chronic diseases” according to a Amino Acids review.

“HMB activates mTOR, one of our primary muscle building pathways, down regulates certain metabolic pathways that lead to muscle breakdown, and up regulates iGF-1 which stimulates the mTOR pathway as well,” says Roper. “It’s always debated when it comes to HMB because some people don’t see effects but many novices see a lot of effects.”


Citrulline is an amino acid that serves as a vasodilator, a substance that increases oxygen delivery to the working muscle by opening the blood vessel, according to Roper. A 2010 European Journal of Applied Physiology study showed found citrulline makes other amino acids more bioavailable and increases production of creatine and nitrite, the chemical that gets broken down into nitric oxide. Nitric oxide helps reduce fatigue which will improve endurance, Roper says.

Beet root powder is another example of a vasodilator. For more on beet root, check out what happened when I took it instead of my usual preworkout.


The testosterone booster category has always been a popular one but in recent years ingredients known for providing anabolic effects are finding their way into pre-workout supplements. In fact, Roper suggests trying these ingredients if you’re looking to gain lean body mass and build strength.

“Tribulus, D-Aspartic Acid, and nettle root extract are examples of ingredients that can help with testosterone production and thus strength gains,” Roper says. “You should definitely be cycling pre-workouts, especially ones with testosterone boosters. If you constantly take these ingredients, your natural production of testosterone can be diminished. Take it for 6-8 weeks, then go off it for a while so your body doesn’t get so used to it.”

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