Stim vs Non Stim Pre Workout | Garage Gym Reviews

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There are two primary types of pre-workout supplements available: those that contain stimulants and those that don’t. Is one better than the other? If you’re wondering what to look for in a pre-workout and find yourself scratching your head when comparing stim vs. non-stim pre-workout supplements, you’re not alone!

As a registered and licensed dietitian, I’m here to help you make an informed decision. Keep reading to learn more about these two types of pre-workout products and which may work best for your training needs.

Medical disclaimer: This article is intended for educational and informational purposes only. It is not intended as a substitute for medical advice. For health advice, contact a licensed healthcare provider.

Stim vs Non Stim Pre Workout: What’s the Difference?

The main difference between stim and non-stim pre-workouts is that stim supplements contain caffeine and possibly other central nervous system (CNS) stimulants, while non-stim supplements do not. Non-stim pre-workouts also contain ingredients to potentially boost your energy and help you work out harder, but these aren’t considered stimulants.

As defined by the FDA¹, a stimulant is “a drug which helps restore mental alertness or wakefulness during fatigue or drowsiness”. Stim and non-stim pre-workouts both aim to improve performance during a workout, but non-stim ingredients won’t necessarily help you feel more awake.

Benefits of Stim Pre-Workouts

Stimulant-based pre-workout supplements almost always contain caffeine as their stimulant of choice since it’s known to be safe and effective when taken within recommended guidelines².

Caffeine works by blocking a compound called adenosine from attaching to adenosine receptors³ in the brain. Adenosine is a neurotransmitter that causes feelings of calmness and drowsiness. By blocking the effects of adenosine, caffeine helps you feel more alert and reduces fatigue.

It can also help improve exercise performance when taken before a workout. Stim pre-workouts often contain other ergogenic (exercise-improving) ingredients besides caffeine, so it can be difficult to tell whether it’s the caffeine or other ingredients providing the bigger boost.

The potential benefits of stim pre-workouts include:

The perception of having more energy
Increased repetitions to fatigue⁴ during strength training sets
Potential for improved aerobic endurance⁵
Small to moderate benefits in muscular endurance and strength⁵, movement velocity, sprinting, jumping, and throwing
Potential for improved reaction time
Potential for increased force production during static squats⁶
Potential for increased training volume⁷ leading to muscle growth and fat loss

Keep in mind that these benefits will only be seen if your pre-workout contains enough caffeine to be effective. According to the International Society for Sports Medicine⁸, it takes anywhere from a dose of 2 to 6 milligrams of caffeine per kilogram of body weight to improve athletic performance.

For a 150 pound person, this ranges from 136 to 406 milligrams of caffeine, which falls well within the FDA-recommended limit for healthy adults of consuming no more than 400 milligrams of caffeine per day.

If a stim pre-workout also contains other ergogenic ingredients, its potential benefits will depend on the amount included in the product. We’ll discuss these other ingredients in more detail in the following section.

Benefits of Non-Stim Pre-Workouts

A stim-free pre-workout can also be helpful for improving exercise performance, no caffeine required. You probably won’t feel as wide-awake as you would with a jolt of caffeine, but these products can help in other ways.

In general, non-stim pre-workout supplements may provide the following benefits:

Potential for increased force production during static squats
Potential for increased training volume and lean muscle mass gains
Potential for increased blood flow—via nitric oxide (NO) boosting ingredients like citrulline and arginine—and nutrient delivery to to working muscles
Potential for improved aerobic and muscular endurance
Less risk of feeling jittery

Of course, the benefits seen with non-stim supplements will depend on which ergogenic ingredients are included. These can vary significantly between brands. Some of the most common non-stim ingredients and their effects include:

Creatine monohydrate: Helps increase muscle stores of creatine phosphate, which helps the body regenerate energy⁹ more quickly during high-intensity exercises
Branched-chain amino acids (BCAAs): Three essential amino acids (leucine, isoleucine, and valine) that help build muscle and may or may not speed up muscle recovery and muscle soreness¹⁰
Beta-alanine: May help improve high-intensity exercise performance¹¹ as a precursor to carnosine, an intramuscular buffer
Nitric oxide agents: Various compounds like L-citrulline and L-arginine that assist in the production of nitric oxide, which helps increase blood flow to the muscles¹²
B vitamins: May help improve energy¹³
Taurine: May help boost fat burn and reduce muscle damage¹⁴
Betaine: May help with the body’s synthesis of creatine and assists with hydration regulation¹⁵
L-carnitine: May help improve endurance performance, increase blood flow to muscles, and reduce blood lactate levels¹⁶

As with stim pre-workouts, potential benefits will depend on the amount of each ingredient included in the product. For example, research has shown¹⁷ that taking 4 to 6 grams of beta-alanine a day is effective for providing ergogenic benefits, so a product that contains less than this may not be very helpful.

Often, supplements that claim to provide a better “pump” contain much smaller dosages of nitric oxide agents than were actually used in research studies. This is usually the case with betaine as well.

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Risks of Stim and Non-Stim Pre-Workouts

Pre-workouts are classified as dietary supplements, which aren’t well-regulated by the FDA in the United States and may provide less-reputable supplement brands the ability to include contaminants like heavy metals, stimulants, or even banned ingredients.

Some of these ingredients are included unintentionally, but some are included to further boost perceived energy levels and muscle-building potential. Many products contain a “proprietary blend” of ingredients that don’t have to be included on the label, so you may not know what (or the amount) you’re really getting.

The possibility of dangerous contaminants isn’t conjecture—incredibly, up to 15% of nutritional supplements tested in one study¹⁸ contained hormones or prohormones. Illegal compounds like methamphetamine have been found as well, although this is pretty rare.

Another risk is the lack of long-term safety testing with pre-workouts. A 2018 review published in the International Journal of Sports Medicine⁶ found that multi-ingredient pre-workouts are safe when taken for less than eight weeks, but their safety over months or years is less clear.

So, should we avoid pre-workouts? Not necessarily. Choosing supplements from reputable brands that are third-party tested for purity is helpful, as are products that are NSF-Certified for Sport. These are trustworthy certifications with high standards for sports nutrition supplements.

RELATED: Pre-Workout Side Effects

Who Should Take Stim Pre-Workouts?

The question of whether or not to take stim pre-workouts centers largely on how caffeine affects you as an individual and whether or not it helps you in the gym. Stim pre-workouts can be helpful if:

You feel more energized or focused during workouts after ingesting caffeine
You exercise early in the morning and need caffeine for an effective workout
You metabolize caffeine quickly and can consume it in the afternoon without leading to sleep problems

RELATED: Best Natural Pre-Workout

Who Should Take Non-Stim Pre-Workouts?

If you’ve noticed that you don’t respond well to caffeine, it’s probably best to avoid pre-workouts that contain that (or other) stimulants. Consider stimulant-free pre-workouts if you:

Have a heart condition like high blood pressure or atrial fibrillation
Experience an overly elevated heart rate with caffeine
Have been advised by your physician to avoid caffeine
Metabolize caffeine slowly
Are pregnant or breastfeeding¹⁹
Get the jitters when taking stim pre-workouts
Have worsened anxiety when consuming caffeine
Exercise close to bedtime
Drink regular coffee throughout the day
Exercise right after eating a meal
Take medications that interact with caffeine²⁰ (e.g., ephedrine, MAOIs, beta-adrenergic agonists, phenobarbital, diuretic drugs, cimetidine)

Pregnant and breastfeeding women should limit their intake to less than 200 milligrams of caffeine²¹ a day and need to be particularly careful not to consume too much from beverages and supplements.

Additionally, if you typically exercise soon after a meal, you’ll end up needing to take a pre-workout right after or with that meal. This can be an issue for proper digestion and absorption of certain nutrients since caffeine interferes with the absorption of iron and calcium²².

Stim vs Non Stim Pre Workout: Final Thoughts

As their names suggest, the main difference between stim and non-stim pre-workout supplements is that stim pre-workouts contain nervous system stimulants (most often caffeine), while non-stim pre-workouts don’t.

Both types of supplements often contain other ingredients that have studies to back up their efficiency in the gym, such as creatine (the most extensively studied ergogenic aid²³), BCAAs, B-vitamins, and nitric oxide agents. These can still be effective for improving exercise performance, but you may not feel the same energy boost and wakefulness that caffeine provides.

When deciding which supplement is best for you, consider the following:

How sensitive you are to caffeine
The time of day you like to work out
Whether caffeine interacts with any of your medications
FDA recommendations: healthy adults should have no more than 400 milligrams of caffeine per day²⁴ to avoid negative side effects
Pregnant and breastfeeding women should limit their caffeine intake to less than 200 milligrams per day²⁴
Choosing third-party tested or NSF-Certified for Sport supplements may help you avoid dangerous ingredients and contaminants in pre-workouts

If you’re still not sure whether pre-workout supplements are right for you, check out our list of pre-workout alternatives.

Stim vs Non Stim Pre Workout: FAQs

Is stimulant or non stimulant pre-workout better?

Stimulant pre-workouts often contain caffeine, meaning they’ll help you feel more energized and awake before you exercise. Non-stimulant pre-workouts won’t do this, but they’ll contain other ingredients that can help you put more effort into your workouts.

If you need a boost of energy before a workout, stim pre-workouts may be more helpful for you. If you’re sensitive to caffeine, work out in the evening, or have been advised to avoid caffeine by a physician, non-stim pre-workouts are likely a better choice.

Is it safe to take non stim pre-workout everyday?

It’s safe to take non-stim pre-workout every day as long as the product contains safe levels of each ingredient and isn’t contaminated with heavy metals, dangerous stimulants, or drugs. Choosing an NSF-Certified for Sport supplement is the best way to ensure the safety of your pre-workout.

Can stim free pre-workout keep you awake?

Stim-free pre-workouts shouldn’t keep you awake since they don’t contain stimulants that excite the nervous system. Vigorous workouts close to bedtime may keep some people from falling asleep quickly to do the adrenaline rush, however. If you’re having trouble falling asleep, it may be because you’re working out too close to bedtime.

These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any diseases.

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Stephanie Wells, MS, RD, LD, ACSM-CPT

Stephanie is a registered dietitian and owner of Thyme to Go Vegan Nutrition Services, a private practice offering telehealth nutrition counseling for vegans, freelance writing, and consulting services. She loves helping others learn how to optimize their nutrition and live healthy, sustainable lifestyles with the power of plant-based foods.