Top 10 Pre-Workout Supplements for Explosive Workouts in 2020

What are pre-workout supplements?

The purpose of a pre-workout supplement is to:

• Boost motivation to hit the gym hard
• Increase muscle pumps
• Increase energy/delay the onset of fatigue

There are several other reasons why people use pre-workouts, but these are the primary reasons why somebody may choose to use them.

A pre-workout supplement uses various ingredients in its formulation in order to accomplish its desired effects. These may include things such as stimulants for energy (i.e. caffeine, yohimbine) and nitric oxide boosters (i.e. arginine, citrulline malate) for enhanced blood flow.

What types of pre-workout supplements are there?

Pre-workout supplements usually come in a powdered form. More often than not, they are usually flavored with a combination of sucralose and acesulfame potassium, which are both artificial sweeteners.

This artificial sweetener blend has become very popular in the sports supplement industry as it removes the unpleasant aftertaste associated with artificial sweeteners. This gives it more of a taste that resembles sucrose (table sugar), making it more palatable.

The serving size of a pre-workout is dependent on the total amount of ingredients in it. You can tell what the serving size is by checking the back of the label, often being measured in grams.

As you start to move past 15 grams or so, that’s when it is usually considered a “higher-quality” supplement since there is more likely to be optimal dosages of effective ingredients. Of course, there are always exceptions to this rule, but this generally applies to most pre-workout supplements.

An even easier way to examine the serving size is to look at the size of the scoop that’s included inside the tub of the product. If you have ever purchased pre-workout supplements in the past, you can compare them and often times realize that the sizes of the scoops can be dramatically different from one another.

The term “pre-workout” is not a regulated term; meaning that this class of supplements does not require that they contain specific ingredients in any particular amount. This is solely up to the discretion of the manufacturer.

What are the most common pre-workout ingredients to look for?

You’ll often see a bunch of ingredients included in a pre-workout supplement. But oftentimes, you don’t know which ones do what and which ones are the best.

Well, look no further, because that’s what our guide is for!

The following list that is about to be included in this guide is intended to serve as just that; a guide.

There is always new and upcoming research in the field of sports supplements. This may mean that some ingredients may be shown to be superior to others later on down the line. But for now, these are the best ingredients based on the current data that we have on sports supplementation.

Caffeine

Ahh yes: caffeine. The most commonly used psychoactive drug in the world (39). And for good reason; it works. And it works well.

This could probably be considered, not only the most common stimulant found in a pre-workout but, the most common pre-workout ingredient overall.

There’s a good reason for this, as caffeine has so many benefits when it comes to exercise. These include things such as increasing power (40), sprinting capacity (41), and the ability at which fat is oxidized (42) (meaning that fat is released in the bloodstream in order to be used as energy by the body).

However, something important to remember here is that the dosage is very important. It’s helpful to know how much caffeine you can personally tolerate before it starts to derail your performance; because more isn’t always better.

Some people have such a high tolerance to caffeine that it takes over 300mg of caffeine for them to feel any stimulatory effect from it (43).

On the other hand, those who are mild caffeine consumers may feel the common side effects of caffeine, such as anxiety and nausea, after a moderate 200mg dose. So it’s always best to assess tolerance before consuming a higher dose than you’re accustomed to.

Related: Top 10 Caffeine Supplements

L-Theanine

You’ll rarely find L-Theanine without it being paired with caffeine in a pre-workout supplement. The reason that pre-workout supplement manufacturers often do this is that L-Theanine is known to encourage relaxation without sedation.

It has the ability to take away the jittery feeling that is often associated with caffeine and helps people to focus better (44).

Because of this unique ability to work with caffeine and not just simply inhibit its effects, it is constantly being tested in pre-workouts to be used as a cognitive booster (45), oftentimes called a nootropic.

Related: Top 10 L-Theanine Supplements

Synephrine

Synephrine is a stimulant that is often known as ephedrine’s “little brother”, which was banned for use in dietary supplements in 2004 due to its very potent stimulant properties along with unpleasant gastrointestinal and psychiatric side effects (46)

Synephrine, fortunately, is safer than ephedrine, but still quite effective. In fact, it has been shown to increase metabolic rate by approximately 65 calories per day (47).

That may not sound like much, but over time, that adds up to some pretty significant calorie burn as a result of the simple addition of a supplement.

Yohimbine

This is quite a potent stimulant, as it has been shown to cause anxiety (48) in a significant portion of the population when taking it, more so than caffeine does. This is usually seen in those who aren’t habitual consumers of stimulants.

However, for those who can tolerate this stimulant, yohimbine has illustrated some impressive fat-loss figures; helping elite male soccer players drop an average of 2.2% body fat in only three weeks (49).

On an unrelated note, it has also been known to help those with erectile dysfunction and aid in libido (50). Take that with it what you will.

Related: Top 10 Yohimbe Supplements

Citrulline Malate

It used to be considered fact that L-Arginine, not L-Citrulline, was the most potent nitric oxide booster (meaning that it increases blood flow to the muscles). But now, research suggests that L-Citrulline is more effective at raising blood levels of L-Arginine than ingesting L-Arginine is (51)! Quite strange, don’t you think?

This increase in nitric oxide has some great effects on your training, such as allowing you to do more work overall (52). This means that you can potentially complete more reps, sets, and maybe even add another exercise into your routine without feeling as fatigued!

Along with this, citrulline malate often makes it less likely that you’ll feel as sore as you normally would the following days after your workout (53). Therefore, you’ll be able to recover faster and possibly even train more frequently.

Now that’s what we like to call progression!

Related: Top 10 L-Citrulline Supplements

Beta-Alanine

Beta-alanine is one of the two amino acids that make up a protein called carnosine, which has a high concentration in our muscles. It is needed to make the muscles contract forcefully.

Beta-alanine itself, despite what many believe, is primarily effective for the activity that exceeds one minute in duration. These include things such as low or moderate-intensity cardio and very high repetition sets of a particular exercise. When activity dips below 60 seconds, the results seen are very insignificant (54).

The primary highlight of beta-alanine is its ability to increase a variable called “time to exhaustion” (55). This variable is key in endurance activities such as cycling and long-distance running.

This translates to a very important training parameter for endurance athletes called VO2 Max, which is a measure of how efficiently the athlete uses oxygen while exercising at their maximal aerobic capacity, This often involves them performing their activity at the highest possible sustainable speed that they physically can.

Interestingly enough, it also has the ability to reduce feelings of fatigue subjectively (56), meaning that the person simply has the conscious thought of being less tired. This is key to when you’re losing motivation towards the tail-end of an exhausting workout.

Related: Top 10 Beta-Alanine Supplements

L-Carnitine

This ingredient is often marketed as a fat burner. However, this purpose has not been well-supported (57).

However, a place where L-carnitine does show notable effects is in its ability to reduce muscle damage. This reduction in muscle damage would have a similar effect to Citrulline Malate; helping you to recover faster!

Recovery is a key component to any training plan and L-Carnitine can help you do just that.

It also has the potential to help those who have just entered into a caloric deficit from a bulking/mass-gain phase. No, not for its ability to burn fat, but for its ability to increase insulin sensitivity (58).

During a typical mass-gain phase, a persons’ insulin sensitivity will tend to drop, making them more insulin resistant (59). This causes a person to lose the efficiency at which they can absorb nutrients from food. When this occurs, then you don’t recover as well due to the limited amount of calories (most importantly protein) they’re absorbing. If you can’t recover, you can’t train well.

Related: Top 10 L-Carnitine Supplements

Creatine Monohydrate

Creatine is the most well-studied sports supplement to date. It has thousands of studies backing up its effectiveness (60). But what’s its purpose in a pre-workout supplement?

Creatine is most famous for its effects on strength (61) and power (62). You’ll find that most athletes who use it are powerlifters, strongmen, and bodybuilders, among other activities where strength and power are a necessity.

However, creatine has been taken out of pre-workout supplements in recent years due to its notorious water weight gain side effect (63).

Some pre-workouts on the market nowadays even offer two of the same versions of pre-workouts, one with creatine and one without.

Related: Top 10 Creatine Supplements

Betaine

Also known as trimethylglycine, betaine really shines when you’re in a fasted state.

When you’re in a fasted state, most often during morning waking hours, cortisol is at its highest (64). Cortisol is more infamously known as the “stress hormone”.

This hormone is catabolic, meaning that it breaks down tissue for energy. This isn’t a selective process though, so that means it could break down that hard-earned muscle during a fasted state, more so especially if you’re currently in a caloric deficit.

Fortunately, taking betaine has been shown to reduce cortisol by a modest 6% (65). This may not sound like much, but over time, the cumulative drops in cortisol can add up and really save you big time from cortisol trying to sabotage those gains!

Related: Top 10 Betaine Supplements

BCAAs

The problem with BCAA’s is that they’re often more hyped than what they’re actually worth. But hold on, this doesn’t mean that they’re completely worthless!

What BCAA’s can do for you is to help you to reduce fatigue during your workouts; mental fatigue that is!

Do you ever feel that sort of “brain fog” that encompasses your brain after several hard sets of a bunch of different exercises and now all you want to do is curl up in your bed and sleep? Well BCAA’s can help you combat that a bit.

Although it can’t necessarily provide a significant improvement to your performance physically, it has often been shown to reduce mental perceptions of fatigue and preserve a person’s cognition (66), or mental thinking abilities.

Related: Top 10 BCAA Supplements

Recommended Dosages of these pre-workout ingredients

• Caffeine: Most commonly, you’ll see researchers use anywhere from 4-6mg of caffeine for every kg of body weight (67), or approximately 9-13mg of caffeine for every lb of bodyweight.
• L-Theanine: Somewhere between 100-200mg alongside 200mg caffeine (68) appears to be the most common.
• Synephrine: Either 10-20mg three times per day or 50mg taken at once (69).
• Yohimbine: 2mg/kg of bodyweight (70), which is equivalent to 0.4mg/lb of bodyweight.
• Citrulline Malate: 6,000-8,000mg daily (71), or 6-8 grams daily.
• Beta-Alanine: Anywhere between 2-5 grams (72) per day. Although it is included in many pre-workout supplements, the effects that help to enhance sports performance are not timing-dependent. This means that it doesn’t have to be taken right before a workout in order to benefit from its fatigue-fighting effects.
• L-Carnitine: Anywhere between 500-2,000mg (73) should suffice.
• Creatine Monohydrate: 5 grams (74) either pre-workout or post-workout.
• Betaine: Anywhere between 2,500mg-6,000mg (75), preferable split into two separate doses if at all possible.
• BCAA: 48-72mg/kg of bodyweight (76), which is approximately 106-158mg/lb of bodyweight.

Stim vs. Stim-Free Pre-Workouts?

It’s becoming more and more popular nowadays to see the phrase “Stim-Free” written on the canister of a pre-workout supplement. What does that mean exactly?

The word “Stim” is simply short for “Stimulant”. A “stimulant” refers specifically to Central Nervous System Stimulants, or CNS Stimulants. This means that they increase your body’s production of “fight-or-flight” hormones such as epinephrine (adrenaline) and norepinephrine (noradrenaline).

Most forms of stimulants found in pre-workout supplements work on what’s called the body’s monoamine system. Simply put, this system involves hormones that increase motivation and reward-seeking behavior such as dopamine and serotonin.

Some of the most common stimulants you’ll find in pre-workouts include caffeine (which is by far the most popular stimulant in the world (77)), synephrine, yohimbine, and theacrine. Sometimes, these stimulants are combined together in order to create a synergy between the ingredients that offsets the side effects of the other.

For example, caffeine and theacrine can often be found together in pre-workout supplements, as theacrine has the ability to offset the side effects of caffeine like jitteriness and anxiety (78).

Now back to “Stim-Free”.

Supplement companies have realized that there are various reasons as to why people want all the benefits of a pre-workout, such as boosting nitric oxide but without the intense stimulation.

This may be due to the fact that the person works until later in the evening and they can’t get their workout in until it’s almost time for the gym to close. It also may be due to the fact that they simply can’t tolerate stimulants as well as other people.

Whatever the reason, a stim-free version of a pre-workout is a viable option for people who may be sensitive to stimulants, while also receiving all the other benefits of taking a pre-workout supplement.

What are the benefits of pre-workout supplements?

Pre-workout supplements are often thought of like some magic potion that gets you all super hyped up and makes you foam at the mouth once you touch the weights.

While some can be like that (with an insane amount of stimulants that can be quite dangerous), the true purpose of a pre-workout supplement should be the following (but of course, this list is not exhaustive):

• Increased blood flow to the working muscles (therefore you get better pumps)
• More energy (usually via stimulant ingredients such as caffeine)
• Increase motivation (usually indirectly as a byproduct of having more energy and containing certain ingredients such as caffeine which increase “feel-good” hormones such as dopamine and serotonin (79)
• Increase focus such as through the use of L-Theanine (80)

Do pre-workout supplements work?

The reason why many people have difficulty choosing a pre-workout supplement is because of the incredible amount of options that are on the market today. So if your pre-workout includes the effective ingredients in the effective dosages as described earlier in this guide, then you’re solid.

Also, whether or not pre-workouts will actually work for you personally depends on your life circumstances, among other variables.

These include things such as your sensitivity/tolerance to stimulants, the energy demands of your job, the time of day that you workout, and the list goes on and on.

Just make sure, with the help of this guide, that you fit in your newfound knowledge and your personal circumstances in order to find the best fit for you.

Are pre-workout supplements legal?

As long as they don’t contain any sort of prohibited substances as declared by the FDA (Food & Drug Administration) (81), they are perfectly legal.

If they weren’t, they wouldn’t be allowed to be sold either in stores or online.

Are pre-workout supplements a steroid?

No, that would make them illegal. If they were to contain any sort of steroids, they would immediately be taken off of the market by the FDA (Food & Drug Administration).

Although pre-workout supplements are regarded as generally safe to take, there are some bad ones that slip through the cracks and cause issues, giving sports supplements a bad name.

One such example was found in 2018 during an FDA investigation (82), where illicit substances were found in pre-workout supplements; including unlabeled anabolic steroids and sildenafil (known as the trade name Viagra™).

Fortunately, this is very rare. As these supplements have raised in popularity, this sort of issue has gone way down, making it even rarer.

Are pre-workout supplements banned in sports?

There are cases every once in a great while about pre-workout ingredients that raise some concerns; usually regarding the ingredients that are classified as stimulants.

For example, the World Anti-Doping Agency regards Higenamine (a stimulant that is occasionally used in pre-workout supplements) as a banned substance in their list of Prohibited Substances (83).

Most other types of ingredients that are included in pre-workout supplements are considered to be safe and acceptable for use as determined by WADA, such as nitric oxide boosters like arginine and beetroot, as well as common stimulants like caffeine.

Should I take a pre-workout supplement?

This is solely dependent on the type of person that you are. If you’re asking if pre-workout supplements are necessary in order to perform well, then the answer would be no.

However, some people find it to be extremely helpful, especially when it pertains to increasing their energy.

For example, the combination of caffeine and theanine (84)  can be very helpful for those who need energy after their workday but don’t want to have trouble going to sleep. This is because theanine counteracts some of the negative side effects of caffeine, such as restlessness and anxiety.

This is just one example, but there’s a lot to get out of a pre-workout, such as:

• More energy
• Better performance (more strength, power, etc.)
• Enhanced blood flow (which means better recovery)

And more!

So if you can fit it into your budget and fell like you need a pre-workout energy boost, then give it a shot!

Who can benefit from taking a pre-workout supplement?

A wide variety of people can benefit from taking a pre-workout supplement. Most notably, those who need a good, strong pick-me-up to get motivated to workout are very drawn to this supplement due to its powerful abilities to give you the focus, energy, and drive that you need to give your workout the best that you’ve got.

It’s also great for those who may be considered intermediate or advanced trainees and they feel as if they’re hitting a plateau of sorts. This could potentially give them the extra push they need to make their training fun and exciting again!

The point here is that there’s no one single group of people that this supplement is good for. What matters most here is whether the specific pre-workout product from that specific manufacturer is a good fit for the person, which is what this guide is all about.

Is there a difference between men and women’s pre-workouts?

To be perfectly honest with you; not really. Sorry to disappoint you.

It’s mostly just a marketing tactic to bring more women into the pre-workout supplement market. There may be trivial differences, such as less caffeine and a pretty pink label. But other than that, stick to the science, not the marketing campaign.

Related: Top 10 Pre-Workout Supplements for Women

Should I take a pre-workout supplement if I don’t work out?

You can but it’s not really advised. Some people actually use it as a replacement for a morning cup of coffee. They’re also usually more effective at increasing energy compared to energy drinks due to the higher amount of stimulants contained in them.

More than likely, though, you’ll just be spending a lot of money on something that you’re not reaping the full benefits from. If you don’t work out, I wouldn’t recommend taking it.

Will a pre-workout supplement increase my libido?

There’s nothing really notable in a pre-workout supplement to necessitate an increase in libido, so most likely not. But there are exceptions to this, as there are some companies out there that include some sort of “anabolic matrix”, or whatever name they prefer, to name a proprietary blend of ingredients that increase testosterone to an extent, such as tribulus Terrestris (85), which has also been shown to increase libido.

However, these types of libido and/or testosterone-boosting ingredients aren’t usually included in high enough doses for a noticeable difference in your libido.

Can a pre-workout supplement make me stronger?

It certainly can, as long as it has ingredients in it that have been shown to help increase strength, such as caffeine (86) and creatine (87), and in the correct amounts too.

Can I just take individual pre-workout ingredients instead of a pre-workout supplement?

If you feel that you don’t need many of the ingredients that are often included in pre-workout formulations, then, by all means, go for it! The purpose of supplementation is to do what is best for you.

Some people are just fine using a caffeine tablet right before their workout instead of a whole pre-workout supplement.

But fortunately, as the number of high-quality pre-workouts begins to rise, you’re bound to find something that fits your needs, goals, and budget. And it’s a lot more convenient too, instead of having to individually mix every ingredient individually every time you’re about to head to the gym.

Can I make my own pre-workout supplement?

Of course! As addressed in the previous question, if you buy the individual ingredients that you feel are best for your goals, then you can simply mix them all up together before you head out to the gym.

Sometimes, it can even be more cost-effective this way.

But just remember, some things don’t mix very well together, such as raw BCAA’s and citrulline malate. Both of these ingredients (citrulline malate in particular), has a tendency to leave a pungent aftertaste, and you don’t have the technology necessary to do things such as seamless flavoring and uniformity of the mixture over all.

It’s not that it’s impossible to make your own pre-workout, it’s just that you should keep these factors in mind when considering what your best option is.

Also, be careful about the dosages you use and your sensitivity to any of the ingredients you choose. I’d highly recommend speaking to a doctor before you try to make your own pre-workout supplement.

How long before a workout should I take a pre-workout supplement?

This can be different depending on the manufacturer of the supplement, but most of them recommend somewhere between 15-45 minutes before your workout.

This is usually stated on the label of the product; most often due to the fact that this is the amount of time that caffeine and other stimulants begin to “kick in” for most people (88).

As you keep taking a pre-workout supplement, you’ll know what works best for you after some trial and error.

Should I eat food with my pre-workout supplement?

That all depends on your personal preference for eating before your workout. Eat at whatever time you normally do before your workout. The effect that food has on the absorption of pre-workout supplements is most likely very minimal, but we have no data to really say for sure.

The most likely scenario is that it may delay the onset of stimulants such as caffeine (89), but the caffeine (along with everything else) will get absorbed just fine.

When is the best time to take a pre-workout supplement?

The best time to take a pre-workout supplement is about 15-45 minutes before your workout, as this is often the recommendation of the manufacturer.

However, it’s advised that you either split your dose in half or skip it altogether if you happen to take a stimulant-based pre-workout supplement in the late afternoon to evening hours. This is because taking stimulants that late in the day may cause insomnia.

How often should I take a pre-workout supplement?

There is no one-size-fits-all answer here. Some people take it every single workout, while others only take it on their most difficult workout of the week (such as leg day). However, none of these are necessarily right or wrong. They’re just preferences.

Some people don’t like the fact that they build up a tolerance to the stimulants in the product, such as caffeine (89). But if this doesn’t bother you, or the stimulants now feel tolerable as opposed to overwhelming then take it before as many workouts as you prefer.

For how long should I take a pre-workout supplement?

The answer to this question is dependent on what ingredients are included in the pre-workout supplement. If it contains stimulants, then it is best to cycle the pre-workout. This could be as simple as using the full canister (often 20-30 servings), so maybe a month’s worth or a little over. After that, stop taking any pre-workout supplement for 1-2 weeks, and then you can start taking them again.

Should I take a break from pre-workout supplements?

As mentioned in the previous question, if the product contains any sort of stimulant, then it is advised to cycle off and take some sort of break from pre-workout supplements. Again, this doesn’t have to be terribly long either; 1-2 weeks off should be plenty of time.

Are pre-workout supplements safe to take?

For most of the healthy general population, they are. Barring any sort of extreme or severe physical condition such as kidney disease or liver failure, ingredients such as creatine, caffeine, citrulline malate, and the like are safe for healthy people to take.

The only thing that healthy people should really be concerned about is the stimulant content, as these ingredients have the widest array of effects on people compared to any other ingredient found in a pre-workout.

Assess your tolerance by taking a half scoop, or perhaps even ⅓ of a scoop to start, and then gradually increase as long as you still feel comfortable doing so. If you’re still concerned, you can always contact your physician, as they can factor your medical history into account and tell you whether or not you’re a good fit for pre-workout supplementation.

We recommend you speak with a doctor before taking ANY supplements.

What are the side effects of a pre-workout supplement?

The side effects of a pre-workout are often associated with the stimulants contained within them. These side effects include, but are not limited to:

• Anxiety
• Tachycardia (fast heart rate)
• Restlessness
• Agitation
• Insomnia
• Acute High Blood Pressure
• Gastrointestinal Issues (i.e. cramping, diarrhea)

This is why it’s very important to assess your tolerance to stimulants before taking a pre-workout supplement. Assess your tolerance by taking a half scoop or less and then gradually increase as long as you still feel comfortable doing so.

Do pre-workout supplements cause damage to the kidneys and liver or any other organ?

With the exception of serious, chronic conditions such as kidney failure or liver disease, pre-workout supplements do not cause damage to the kidneys, liver, or any other organ for that matter when taken responsibly and according to the manufacturer’s directions.

Taking more than recommended may cause stimulant overdose, which can cause negative effects on the heart (90).

ALWAYS follow the manufacturer’s directions on the label.

Do pre-workout supplements cause acne?

This is very unlikely, as theirs no ingredient present in any common pre-workout formulation that has been shown to cause acne.

Do pre-workout supplements cause hair loss (alopecia)?

No, there are no ingredients in pre-workouts that have been known to cause alopecia.

Will pre-workout supplements cause testicle shrinkage?

No, that’s complete nonsense. Remember, pre-workout supplements don’t contain anabolic steroids, which do happen to cause testicular shrinkage.

Can I take a pre-workout supplement with other supplements?

Yes, you most likely can. As there are a wide variety of ingredients used in pre-workouts along with an even more vast array of supplements that somebody could take, there is a small chance that there could be an interaction between supplements.

Unfortunately, it would be impossible to list every single one (if there even are any).

Your best bet would be to either talk to your doctor or your pharmacist, as they are well-trained regarding interactions between supplements and drugs.

What are the best supplements to take a pre-workout supplement with?

The best supplements to take with a pre-workout supplement are the ones that best pair with your goals, along with what’s already included in the pre-workout supplement that you have.

For example, let’s say you’re looking to build muscle mass and you bought a pre-workout with the best ingredients for you; 6,000mg of citrulline malate for good blood flow and sick pumps (91), 300mg of caffeine for solid energy (92) to get you through your grueling session, and some other really effective ingredients. However, you notice that it doesn’t contain creatine, which you heard is great for packing on muscle and strength. What do you do?

You can simply buy it in isolation (it’s super easy to find as well as extremely affordable) and add it to your pre-workout. The plus side in this example is that creatine often mixes very well with liquids.

The point here is that you’ll really only want to use additional supplements alongside pre-workout supplements in order to fill in the gaps of your current pre-workout supplement. But if your current pre-workout (or the one you’re about to buy right after this guide) has everything that you need, then you simply don’t need anything else.

Should I take a pre-workout supplement when I’m trying to lose weight?

Yes, why wouldn’t you? It actually may even be more beneficial to use it during a fat-loss phase due to the stimulants that are often included in it.

Stimulants such as caffeine and yohimbine have been shown to increase metabolic rate. In other words, they help you burn more calories during the day. All of these extra burned calories add up after a while, which leads to faster fat loss!

Will I Lose Weight or Muscle Mass If I stop using a pre-workout supplement?

The only reason it would do this is if you become dependent on the supplement to get motivated to workout and perform at your best. This is what can happen if you don’t cycle your pre-workout supplement properly.

But to answer the question precisely, the answer is no. A pre-workout supplement cannot directly cause you to lose weight or muscle mass.