How building muscle (fast) actually works

Most people have no idea why fitness influencers recommend training hard or consuming enough protein to build muscle…

In today’s newsletter I want to break down my model of how we build muscle, what it has to do with muscle protein synthesis, and how we can maximize it.

I’m going to show you the simple levers you can pull to unlock faster muscle growth — without wasting time on stuff that doesn’t matter.

Let’s dive in.

1. How do we build muscle?

Our body is constantly undergoing muscle protein turnover (MPT) to keep our muscles healthy by recycling old or damaged proteins and synthesizing new ones.

Muscle protein turnover (MPT) consists of two processes—muscle protein synthesis (i.e., the creation of muscle proteins, MPS) and muscle protein breakdown (i.e., the breakdown of muscle proteins, MPB).

If we would like to display muscle protein turnover on a graph, it could look like this (for an individual who trains effectively):

We build muscle whenever muscle protein synthesis exceeds muscle protein breakdown (MPS > MPB).

In the new graph, the pink area under the MPS curve and above the MPB curve represents the muscle we build.

This means, if we want to build muscle fast, we should want to maximize MPS and minimize MPB as much as possible and as consistently as possible.

But how do we do that?

2. What influences MPS/MPB?

To find out how to maximize MPS and minimize MPB, we need to know what even influences these processes.

Here’s a list of everything that influences MPS/MPB:

• Resistance Training (Mechanical Tension & Motor unit recruitment)

• Protein (Intake, Timing, Quality)

• Energy Availability

• Genetics

• Training Age/Already-Built Muscle Mass

• Chronological/Biological Age

• Sleep & Recovery

• Cortisol & Stress

Now, there are many factors we can’t influence:

• Genetics

• Training Age/Already-Built Muscle Mass

• Chronological/Biological Age

So, let’s disregard them.

These are the ones we can influence:

• Resistance Training (Mechanical Tension & Motor unit recruitment)

• Protein (Intake, Timing, Quality)

• Energy Availability

• Sleep & Recovery

• Cortisol & Stress

Commonly, these get put into three (or four) buckets.

1. Training

2. Nutrition

3. Recovery

4. (Consistency)

Now, we can understand why.

1. Training

   1. Resistance Training (Mechanical Tension & Motor unit recruitment)

2. Nutrition

   1. Protein (Intake, Timing, Quality)

   2. Energy Availability

3. Recovery

   1. Sleep & Recovery

   2. Cortisol & Stress

And since we want to maximize MPS and minimize MPB as much as possible for as long as possible, we could include consistency.

Here’s a slight catch, though.

We can’t lower MPB below a certain point, and it is much less variable than MPS. We can only lower MPB if it was elevated above the norm in the first place (e.g., due to stress).

That’s why the main focus of the next section will be about how to maximize MPS.

In doing so, we will likely do everything that needs to be done to minimize MPB anyway.

3. How do we maximize MPS?

So, let’s dive into how to maximize MPS with our four variables—1) resistance training, 2) protein (intake, timing, quality), 3) energy availability, and 4) sleep.

This section will focus on principles. The exact application of these principles doesn’t matter. There’s no magic program or magic meal plan that will explode your gains.

Just stick to the principles, however you do that in practice doesn’t matter (or very little).

3.1 Resistance Training (Mechanical Tension & Motor unit recruitment)

The most important factor to maximize MPS is resistance training.

You can feed a coma patient as much protein and food as you want, he won’t build any significant amount of skeletal muscle (the type of muscles we want).

Why? Because there’s exactly 0 reason for their body to do so. There is just no stimulus.

The reason some studies seem to find slight muscle gain during a calorie surplus, even without resistance training, is because everyday physical activity still provides a minimal stimulus.

Anyway, how do we maximize the stimulus from resistance training?

To understand that, we need to know what even creates the stimulus.

The seemingly only and best supported muscle growth stimuli are mechanical tension and muscle fiber recruitment.

And you probably need both 1) high mechanical tension and 2) high muscle fiber recruitment at the same time.

What is mechanical tension?

Mechanical tension represents the internal load (force) the muscles experience when contracting against resistance. It is higher the more the bar speed slows down due to being close to failure.

What is muscle fiber recruitment?

Muscle fiber refers to the amount of motor units being recruited during a set of a resistance exercise. In the beginning of a set more low threshold motor units will be activated, the more they fatigue, the more motor units need to be recruited to keep producing force. That’s when the higher threshold motor units will be activated. If a set is sufficiently heavy, nearly all motor units will be recruited from the start.

To maximize both, we want to train close to failure (0-1 RIR) in the 4-12 rep range with moderate to heavy loads.

Training in higher rep ranges can lead to less motor unit recruitment due to CNS fatigue.

3.2 Protein (Intake, Timing, Quality)

This is the second most important factor to maximize MPS.

Amino acids are the building blocks of muscle tissue, as they are assembled into new muscle proteins during muscle protein synthesis (MPS).

If we don't consume enough amino acids, the body simply won't have the raw materials needed to build new muscle tissue, and muscle growth will not occur.

It's not just about quantity, though — the right types of amino acids must also be present. Think of it like baking: if you're missing one key ingredient, you can only bake as many batches as that limiting ingredient allows before production stops.

Similarly, in muscle protein synthesis, if even one essential amino acid is missing or insufficient, the body can only synthesize new muscle proteins until that amino acid runs out, at which point MPS comes to a halt.

Ideally, we want to provide our body with enough of the right ‘ingredients’ throughout the day to maximize baking uptime, i.e. we want to feed our bodies enough of the right amino acids throughout the day to maximize muscle protein synthesis uptime.

How do we do all that in practice?

It’s simple.

1) Eat 1+ gram of 2) high-quality protein per lb of body weight, 3) evenly distributed across 3-6 evenly spaced meals throughout the day.

What are high-quality protein sources?

• lean meats (chicken, turkey, minced beef, etc.)

• lean dairy (e.g., low-fat cheese, Greek yogurt, skim milk, etc.)

• eggs

• whey or casein supplements (basically dairy proteins)

• fish (I have no idea about fishes as I don’t eat them, sorry…)

• probably some vegan sources (again, I have no idea about that)

I am more and more of the opinion that consuming more protein than 1.6 g/kg is beneficial. I know studies often find that this is not the case, but anecdotally I think it’s true.

There was even a recent article that came out by stronger by science which seems to claim that consuming more than 2.2 g/kg (~1 g/lb) might even be beneficial.

Here are the takeaways of the article:

3.3 Energy Availability

This isn’t as important as I once thought.

As long as you’re not too lean (10+% body fat), and are consuming pretty close to maintenance calories or above, you can build muscle.

Yes, even in a slight deficit.

Energy availability refers not only to short-term energy balance via calorie consumption, but also long-term energy availability via fat stores.

This explains, why overweight people can build muscle while in a deficit. The bodies of overweight people have enough long-term energy availability to allow for muscle growth while in a calorie deficit.

Being in a deficit (i.e., consuming calories below maintenance), can and probably will decrease your muscle growth when compared to being closer to maintenance or above, but it’s possible as long as the deficit isn’t too high.

Further, it seems consuming a sizable calorie surplus isn’t necessary to maximize muscle growth.

We can maximally synthesize 5-20g of muscle protein per day. To do that, we need a calorie surplus of about 20-100 kcal.

But, since trying to stay at maintenance likely leads to small amounts of weight gain over time, we can stick to consuming close to maintenance calories and see how our body weight changes over time.

As long as we are not gaining more than 0.15-0.5 kg (~0.3-1.1 lbs) per month, we should be fine.

If we’re gaining faster than that, it could be that we’re gaining needless amounts of additional fat while not increasing our muscle gain.

3.4 Sleep

Sleep also really isn’t that important as long as you’re not fucking up your sleep through chronic sleep deprivation.

Just try to sleep 8+ hours every night and you should be golden.

4. Summary

1. Train close to failure (0-1 RIR) in the 4-12 rep range with moderate to heavy loads

2. Eat 1+ gram of high-quality protein per lb of body weight, evenly distributed across 3-6 evenly spaced meals throughout the day

3. Don’t gain more than 0.15-0.5 kg (~0.3-1.1 lbs) per month, or you are likely gaining needles amounts of fat

4. Try to sleep more than 8 hours every night

I hope you found it helpful.

Thanks for reading, Jonas