Building muscle is a process that can be learned and achieved fairly easily. To assist you in navigating through that process, in this blog, I’m going to explain how to do it in five levels of increasing complexity, starting with the most basic explanation and getting more detailed as we go along.
While preparing for this blog, I consulted with a number of different experts, including a professor in Muscle Metabolism (Dr. Jorn Trommelen), an industry leader in the field of Biomechanics (Andrew Vigotsky), and an active researcher in the field of Strength and Conditioning (Dr. Eric Helms). I’m also a Pro-Natural Bodybuilder myself and I’ve been studying the science behind getting jacked for over a decade, while coaching people from around the globe.
Pulling primarily from these sources, along with some specific research analysis that are referenced at the end of the blog, I’ve outlined these five levels as succinctly as possible so that you’ll have little difficulty pinpointing your current level of understanding on how to build muscle.
Before we dive in, I have a favour to ask. As you read through the various levels, take note of the specific level you got to before you started zoning out or getting lost. Let us know in the comments at the end of the blog.
LEVEL 1: NOOB
Explaining muscle growth to a non-lifter
Building muscle is actually quite simple. All you really need to do is lift weights and eat protein.
Protein, of course, is the macronutrient found in foods like fish, chicken, meat, dairy, beans, lentils, and protein powders. And when you weight train, your muscles start to think, well if we’re going to keep lifting these heavy weights, I’d better start to get some bigger muscles to make this easier.
This is called an Adaptive Response. It’s kind of like when you play guitar. Your fingertips start to get harder and grow calluses as an adaptive response to pressing against the strings. It hurts at first, but then it gets easier as you build the thicker skin layer.
However, lifting weights isn’t quite enough on its own to build muscle. In order to build something, you need building blocks and when it comes to muscle, the building blocks are called Amino Acids, which you get by eating protein. In essence, when you lift weights, you’re telling the muscle it needs to get bigger. Then, when you eat protein, you’re giving the muscle the building blocks it needs to actually grow.
LEVEL 2: NOVICE
Explaining muscle growth to a new lifter
In reality, it’s probably not quite good enough to just lift weights and eat protein to get really solid results.
For example, if for two years you've been lifting the exact same weight for the exact same reps, you're likely struggling at keeping the muscle growing. Sure, you’ll see some decent growth at the beginning because you’ve never lifted any weight before. But soon enough, that weight will no longer be challenging enough to present a sufficient stimulus for your muscle to continue growing.
This is why we need to expand the ‘lift weights part’ to lift weights with an emphasis on progressive overload.
Or, just increasing some training parameter over time.
From workout to workout, you'll need to add a little bit of weight or add an extra rep using the same weight.
For example, let’s say you’re trying to grow your biceps. Rather than doing three sets of ten reps with the same weight week after week and month after month, it’d be much more effective to do what’s illustrated in the following diagram.
At a certain point, you may not be able to increase the weight or reps each and every time, but that’s okay. There are still other ways to apply progressive overload.
Consider adding an extra set with the same reps and the same weight, doing something as simple as controlling the negative a little better, feeling a stronger mind-muscle connection where you more consciously feel the muscle squeezing and stretching as you lift, or swapping out for a new exercise and starting that overloading process again.
Also, on the nutrition side, you can do quite a bit better than just saying “eat protein.” To be more specific, the latest research shows that landing between 1.6-2.2 grams of protein per kilogram of body weight per day (about 0.7-1 gram per pound) is a good target for maximizing muscle gain.
For example, if you weigh 165 pounds or 75 kilos, you’d want to be eating somewhere in the range of 120-165 grams of protein per day for general muscle building. Although there may be some advantage in going a bit higher in certain advanced situations, this is a sufficient range for most.
It’s worth noting that if you’re very high in body fat, the grams per unit body weight approach won’t work as well. Let’s say you’re 300 pounds. In this case, you don’t really need 300 grams of protein per day. I simply prefer to use 1 gram of protein per centimeter in height because it works independently of body fat percentage.
Let’s check this example.
It’s not a perfect system, but it’ll get you in the right ballpark.
There is some evidence to suggest that spacing your protein across three to five meals throughout the day might be more ideal. If that suggestion holds true, it’s certainly much less important than simply hitting a daily protein target.
In fact, contrary to common belief, training is a much more powerful contributor to muscle growth than diet, and by quite a long shot.
So while it is true that a caloric surplus will drive muscle growth more effectively and dietary manipulations like protein timing can have some impact, I’m going to focus the remaining levels on maximizing the muscle response through resistance training.
LEVEL 3: AVERAGE
Explaining muscle growth to a regular lifter
Focusing on progressive overload is smart, but it still leaves a lot to be desired in the gym. For example, it doesn’t tell us:
“How HARD should we push it?”
“How many SETS should we do?”
“How many REPS should we do?”
“How HEAVY should we lift?”
Because of this limitation, next, I want to take a quick look at what the research says about the so-called Acute Training Variables.
This is the most fundamental variable for growth because no matter how much you optimize all the other stuff, if you aren’t pushing it hard enough, the muscles simply won’t grow - at least not optimally.
There’s currently a raging debate within the scientific community about exactly how hard we should push each set. A relatively small group of experts insist that all sets should be taken all the way to muscular failure. That is, your set is not complete until you are unable to complete another rep despite maximum effort.
However, the mainstream scientific consensus appears to be that it isn’t necessary to take sets all the way to failure, but you do need to be pretty close. You shouldn’t be leaving more than two or three reps in the tank for most of your sets.
Of course, there are a few exceptions where leaving five or more reps in the tank does make sense for recovery, especially when training primarily for strength. But as a general rule, most of your sets should be pretty close to failure, so you do need to push it hard - maybe harder than you think.
Technically referred to as the amount of work you do, this training variable was historically calculated as the number of sets times the number of reps times the amount of load.
But as of 2015, most practitioners began to think of volume simply as the number of hard sets you do.
It’s become a popular meme to think of volume as the “primary driver of hypertrophy.” Allow me to clarify that if I’ve ever said this, I no longer think it's the case.
Rather than more volume leading to more growth, what we instead see is a sort of inverted U trend. This means that more volume leads to more growth only up to a point, past which further increases don’t do anything extra. And then at a certain point, adding more volume seems to be counterproductive. There exists this volume sweet spot that seems to be a bit different for everyone.
I’ve noticed that many people are already doing more volume than they really need and would probably benefit more by reducing their volume and focusing more on effort and execution. The main point here is that you should experiment and figure out what dose of volume gives you the best balance of gains and recovery.
Still, based on what we know from the current science, something around 10-20 sets per body part per week seems to be a good range for most people and most muscles.
For example, if you’re running an upper-lower split that has you in the gym four days per week, your chest volume might look something like this.
Despite its popular conflation with effort, intensity refers to how heavy the weight is. You can either lift heavy weights for low reps or light weights for high reps.
This leads to the question, “what’s the best for muscle growth?”
It turns out that as long as you’re taking sets sufficiently close to failure, you can maximize hypertrophy using high reps or low reps, or a combination of both.
Research has shown that reps as low as three and as high as 30 reps all cause similar muscle growth. However, there does seem to be a limit to how light you can go.
New data shows that when you lift weights lighter than 20 percent of your 1 rep max, you do see significantly less growth. In fact, the average rep count that subjects got with that load was 67 reps; not a very practical way to train.
The traditional 6-12 rep zone is kind of a myth in the sense that research shows that you can go well outside that range and still grow, as long as you’re training close to muscular failure. Still, I think there is some value in that 6-12 range because once you start dipping down below six reps, you can risk unnecessary strain on your joints and it can be practically more difficult to accumulate enough volume.
The more you go above 12 reps, the more you risk just burning yourself out as higher rep sets are harder to recover from.
For practical purposes, I suggest that the majority of your sets be in that 6-12 rep range or maybe even in the 15 zone. Smaller chunks of your workout then can be dedicated to lower reps for continued strength progression and higher reps for stimulative variety.
Personally, I tend to favor multi-joint compound movements like squats, presses, and rows in my own training because they give me more hypertrophic bang for my buck. They do so by activating large amounts of muscle mass while promoting more efficient total body strength gain.
While I definitely think mastering these basic compound movements is important, single joint isolation exercises certainly have their place, especially when it comes to targeting smaller muscles like the biceps, rear delts, side delts, and abs. These muscles can be overpowered if you focus on compound lifts exclusively.
Luckily, when it comes to muscle growth, there are no mandatory exercises and so after mastering the basics, it’s once again important to experiment with different movements and movement variations to figure out what works best for you and your body’s mechanics.
It seems like most people have flipped from thinking that you should only train each body part once a week on a split similar to the one shown below, otherwise you’re going to over-train and melt your muscle away.
These days, most people think that if you train on a bro split like the above, you’re never going to make any gains at all because science says so.
In reality, the latest research actually shows that frequency in and of itself likely plays a relatively minor role in muscle growth. The latest studies show similar results between hitting a body part once a week and hitting that same muscle three plus times per week.
However, I still generally recommend hitting a muscle at least twice a week and I do prefer splits like upper lower and full body over the traditional body part split. Typically, the twice per week option allows for more volume per week and higher quality volumes per workout.
As long as you’ve got all the other variables in place, are recovering properly, and are consistent over time, this is an area of programming that probably deserves less of the spotlight than it tends to get.
LEVEL 4: ELITE
Explaining muscle growth to a serious lifter
With progressive overload and the main acute training variables in mind, at this point, I’d like to get a bit more granular and take a closer look at what’s actually driving muscle growth physiologically.
In 2010, Dr. Brad Schoenfeld published a landmark paper with over 500 citations that introduced the 3-Factor Model of muscle hypertrophy. This model proposed that there are three main things driving muscle growth.
#1. Mechanical Tension is the type of force that tries to stretch a muscle fiber.
One way to visualize this is like a tug of war. As each side pulls, tension is generated in the rope. You can think of it like, not only are the people pulling on the rope, but the rope is also pulling back on the people.
Similarly in the muscle, tension is passively created when the muscle is stretched and tension is actively created during contraction when actin molecules are pulled by myosin heads.
Currently, within the scientific community at large, tension is absolutely undisputed as the primariver of hypertrophy.
#2. Muscle Damage is basically exactly what it sounds like. Physical damage to the muscle occurs through micro-tears and other cellular disruption. You can observe this under a microscope where you see the normal pattern of muscle being seriously disrupted after training.
Some researchers believe that this type of damage is at least partly responsible for the delayed onset muscle soreness that you sometimes feel in the days following training, although the soreness phenomenon is no doubt caused by a number of factors and still isn’t fully understood. As they have for many years, many people still assume that getting sore should be the goal of training since soreness comes from muscle damage and muscle damage causes muscle growth.
However, the latest science shows that that first claim is questionable and the second claim is most likely not true.
Of course, the most common sense way to think about this is realizing that running a marathon would cause tons of muscle damage, yet wouldn’t do anything good for muscle growth.
In fact, a review paper from Wackerhage and Colleagues pointed out that if anything, damage in this context would seem to decrease muscle growth.
Even in a weight training context, damage doesn’t seem to be doing much good. The study from Damas and Colleagues argued that over the long run, damage doesn’t even correlate with hypertrophy.
As shown in the following figure, early on in a training program you see a huge amount of damage. This could be why one gets very sore when starting a new routine. While there is an associated early spike in muscle protein synthesis, the vast majority of that synthesis is directed to repairing damaged muscle tissue rather than building new muscle tissue from scratch. It’s only after that damage decreases that muscle protein synthesis is directed toward new muscle hypertrophy.
While folks playing devil’s advocate could argue that studies show that eccentric training causes more muscle damage and studies also show that eccentric training causes more muscle growth, I would simply respond that correlation doesn’t imply causation and it seems more likely to me that the extra growth you see from eccentric overloading could simply be coming from the fact that you can simply overload the muscle more heavily during an eccentric contraction causing more tension in the muscle.
I should say that if we’re being really honest, we don’t actually understand muscle damage all that well. Even the methods of simply measuring muscle damage have been contested by prominent researchers.
The bottom line is that any theory that uses muscle damage to explain muscle growth is speculative at best, and unfeasible at worst.
#3. Metabolic Stress refers to the accumulation of metabolites (like lactate and hydrogen ions) and the muscle hypoxia (oxygen deficiency) that often follows weight training.
Metabolic stress is often associated with the massive skin-tearing pumps that you get from high-rep workouts.
If muscle damage and its ensuing soreness is unlikely to be driving muscle growth, surely the pump in its associated metabolic stress must be doing something. I mean, even Arnold Schwarzenegger seemed to recognize this.
“The greatest feeling you can get in a gym or the most satisfying feeling you can get in the gym is the pump. Your muscles get a really tight feeling like your skin is going to explode any minute. You know, it’s really tight, it’s like somebody blowing air into your muscle. It just blows up and it feels different. It feels fantastic.”
Well, while the pump does feel good and certainly can make training more enjoyable, and perhaps even provide some feedback that you’re actually hitting the muscle that you’re trying to target, it most likely isn’t driving hypertrophy because there are just too many examples of where the relationship between metabolic stress and muscle growth breaks down.
Blood flow restriction training (BFR) causes tons of metabolic stress but doesn’t enhance hypertrophy on its own and doesn’t even work in conjunction with training unless the training methods are highly sub-optimal. Even in this case, it still seems to point back to tension.
When I spoke with one of the authors of this popular blood flow restriction study, Dr. Jorn Trommelen, he pointed out that any benefit seems to be tension related.
“Would you argue that the impact of BFR essentially leads back to just creating more tension in the muscle? Do you think it still goes back to tension?”
“Yeah! It's just BFR is like cheating 20 reps extra in a sense. It’s the same effect; it just happens earlier.”
The consensus among researchers is that perhaps tension alone is the primary driver of muscle growth and therefore, the primary goal of our training should be to maximize tension above anything else.
How do we do that?
The practical application is actually quite simple. We need to apply progressive tension increases to the muscle itself. This means we need to lift with good consistent technique while using the acute training variables and progressive overload to push the level of intramuscular tension up over time.
Also, paying attention to things like the mind-muscle connection, at least on certain exercises, and eccentric control should also help, as those aspects of lifting have been shown to increase intramuscular tension.
LEVEL 5: PRO
Explaining muscle growth to a serious lifter
We know that mechanical tension is the main thing driving muscle growth, but what happens next? How do we get from a mechanical stimulus like tension to a biochemical signal that commands the muscle to grow?
Dr. Trommelen explained this to me in terms of blocks of dominos. He said that when one thing is activated, it passes on the signal to the next thing, and the next thing, and so on.
But if you’re smart, you don’t just build one chain of dominos. You build out all these side chains so that they fall in a bunch of different directions. When it comes to muscle growth, there isn’t just one pathway with one outcome, but rather many different interconnected pathways with many different downstream effects.
With that in mind, let’s start at the top.
We lift a weight heavy enough that it creates active mechanical tension within the muscle. This is called the stimulus. The stimulus is sensed by mechano-sensors which sort of feel that the muscle is being pulled into tension and pass that signal on.
Based on the latest research, it isn’t perfectly clear exactly which molecules are doing this sensing, but the top candidates include Costameres, which are collections of protein that sit in the muscle fiber membrane and are responsible for holding muscle fibers together and transferring force between muscle fibers during contraction.
There’s also Titin, which as a fun fact is actually the largest protein we’ve ever discovered in humans, and because it runs parallel to the muscle fiber itself, it could theoretically be responsible for sensing mechanical changes like stretching, but probably only at long muscle lengths.
Then there are Filaments, which bind to the famous actin proteins that slide during contraction, making them a really good candidate for sensing tension.
For the record, I read through the latest paper on all this sensing stuff from 2018, and I’ll just say that this area of research is not well understood yet. To quote the authors directly:
“Conclusively identifying major hypertrophy stimuli and their sensors is one of the big remaining questions in exercise physiology.”
Still, we can paint the rest of the picture with a broad brush for now.
From the mechano-sensors, a signal gets sent to a beast mode molecule called mTOR, which is a major regulator of cellular growth in general. Interestingly, because of its responsibility in making tissues bigger, it’s also implicated in many cancers.
From there, mTOR goes to the nucleus and tells the DNA machinery to produce a messenger RNA (mRNA) strand, which you can think of as a set of blueprints for building new muscle.
Through a process known as Translation, those blueprints are sent to a Ribosome, which is like a muscle protein-building factory that manufactures a string of amino acids based on the blueprint from the mRNA. This step is what we’re actually talking about when we say muscle protein synthesis.
Through this translation process, many different proteins will be synthesized, some of which will be the big contractile proteins that make us more jacked. Others will be more ribosomal proteins or mTOR proteins themselves, ensuring that anabolic growth potential remains high in the future.
If this rate of synthesis exceeds the rate of breakdown, protein balance is said to be positive and in that case, new contractile proteins are incorporated into muscle fibers, resulting in what’s called Myofibrillar Hypertrophy. It’s then that we are on our way to increased muscle size overall.
Keep in mind that all of what we just uncovered is really just one string of dominos. There’s also this other path that’s triggered by amino acids in the protein we eat. In this case, amino acids are transported inside the cell and the amino acid leucine also activates mTOR.
For the record, we seem to need about three grams of leucine to stimulate mTOR. These three grams can be found in about 20-25 grams of high-quality protein, although some research has shown greater anabolic responses with higher protein doses.
Although it may be possible to crank mTOR activity higher with more leucine, it’s important to realize that the stimulative impact of leucine is much shorter than the stimulative impact of weight training.
For maximum mTOR stimulation, then, you need both training and leucine, with leucine essentially complementing the stimulative effects of weightlifting.
The other eight essential amino acids make their way to the ribosome where they’re used as the fundamental building blocks for creating new muscle.
Another pathway that I’ll briefly mention is that of Testosterone.
Even though modifying testosterone within the natural range plays a relatively minor role in muscle growth, when you inject high-dose testosterone, the hormone crosses the muscle cell membrane and either binds to an androgen receptor directly or is converted to DHT. This, in turn, binds to the androgen receptor, and then that complex enters the nucleus and tells the DNA to start cranking out more blueprints, turning up that muscle protein synthetic process even more.
If I were actually discussing muscle growth with an expert, there are a lot of other things I’d want to discuss, including Sarcoplasmic Hypertrophy.
So far, we’ve been focusing on MyoFibrillar Hypertrophy, the growth of actual contractile tissue. But there’s some new solid evidence supporting so-called Sarcoplasmic Hypertrophy, which is the growth of all the other stuff inside the muscle fiber like glycogen, organelles, and other non-contractile proteins.
I might speculate that higher rep and higher volume training might bias the muscle towards sarcoplasmic growth, but then the expert, depending on how open they are to guesswork, might shut that down for lacking evidence.
I’d also definitely want to talk about Myonuclear Addition, the idea that all this muscle protein synthetic stuff still seems to be limited by the number of nuclei or command centers that you have in your muscle cells to begin with.
When satellite cells that surround the muscle cell donate their nuclei, it could theoretically allow the muscle cell to crank out more new muscle protein and build more muscle.
But then the expert might push back that that theory is actually pretty speculative and we can’t even rightly assume that nuclei are in fact limiting factors for hypertrophy until we get more science in our hands.
A curious bystander might ask why does any of this matter anyway?“What’s the point of this level of research?”
Maybe the expert would respond by saying something like knowledge has value for its own sake.
Maybe they’d point out a few of its many medical applications, such as in understanding sarcopenia or muscular dystrophy, or maybe they’d say that they’re trying to figure all this stuff out just in case there’s a new pathway that can actually feed back into training recommendations.
Some may suggest that maybe we’ll be able to use this research to develop an exercise pill someday that creates the same cellular effect as weight training without having to spend nearly as much time in the gym - a sort of “steroid” without side effects.
Since I’m getting well over my own head at this point, I think I’m gonna leave it there for this one.
If you guys made it this far, please let me know by commenting “I’m ready for level 6” and I’ll see if I can make that happen in another blog.
If you’d enjoy a summed-up video of this blog, it’s available on my YouTube channel.
That’s it for this one, guys. Thank you so much for sticking around! I’ll see you all here for the next blog.
Total Daily Protein Target:
Mechanisms of Muscle Hypertrophy:
*Footnote on Metabolic Stress:
While I personally think it makes the most sense, it actually isn't perfectly clear if shorter rest periods do in fact increase metabolic stress, compared to longer rest periods. For example, this study (https://sites.kowsarpub.com/asjsm/art...) found that blood lactate levels increased similarly during a full-body workout when resting either 30, 60, or 120 seconds between sets. Still, since this study only measured lactate levels and not H+, hypoxia, phosphate, etc. I think the assumption that shorter rest periods would lead to more metabolic stress (via increased fatigue) is nonetheless a reasonable assumption in the absence of direct empirical data.
*Footnote on BFR:
Some might argue that BFR does actually enhance muscle hypertrophy. However, if that effect exists, metabolic stress hasn't been shown to be the main causative factor. Plus, BFR only seems to augment hypertrophy if the training methods are suboptimal (both light weights and far from failure).
Blood Flow Restriction:
Hypertrophy Stimuli and Sensors: