Guest article written by Tom Sheppard of Phoenix Performance Training.

We all want to be jacked. Even those of us who claim to do it for health benefits, performance (in strength sports or other sports), or whatever other reason. Being more jacked gives us more confidence, makes moving house infinitely easier, and helps make the sad head voice go away for a little while.

So, considering that just about everyone in the weights room is after hypertrophy in at least some capacity, very few understand what stimulates hypertrophy and even further understand how much work they need to do to achieve it. 

The goal of this article series is to help address these points. 

In this first article, we will briefly cover the mechanisms that drive hypertrophy. This will lay the foundation for what we will cover in the later articles about how we set up effective programming. So yes, this first article may be a little dry (read: very boring) for some of you. But how can we program for hypertrophy if we don’t know what CAUSES hypertrophy? So simply see this as an investment in future gains.

So have your chicken and rice ready, and let’s begin…..

What Stimulates Hypertrophy?

Until quite recently, the primary driver of hypertrophy was a hotly debated topic. Some thought it was volume, and some thought it was mechanical tension, while others thought it was the 9 ancestral tenants (if you don’t get that joke/reference, then consider yourself lucky).

However, a lot of great research has been done over the last 10-15 years to help clear this up, especially by the likes of Brad Schoenfeld. Meaning that we now have a pretty clear of what does, and does not, contribute to the stimulus of hypertrophy. 

Factor 1 – Mechanical Tension

It’s now become clear that mechanical tension is the primary stimulus for muscle hypertrophy. But what exactly does mechanical tension mean in this circumstance? 

Put simply; it is the stress that is applied to the muscle fiber from an external resistance. Now, we can achieve a high degree of mechanical tension from the start of a set by using heavier loads. That way, the muscle fibers are under a high degree of stress from the very start of the set. But that isn’t the only way we can achieve this.

The mechanical tension created by a load will increase from rep to rep as fatigue accumulates. On average, muscle fibers will fatigue at around 3-4% per rep, so if we start our set with a weight that represents 60% of our 1-rep max, the RELATIVE LOAD (or intensity) will increase with each rep until we reach failure. Failure simply happens when the relative load exceeds 100% of our capacity at that moment in time. 

This is summed up in Table 1 below.

Table 1 – The relationship between rep number, relative intensity, and fatigue. Those listed in red are “maximally effective reps.” The 12th rep would be a failed rep due to relative load exceeding 100%

When training for hypertrophy, we need 80% relative load/intensity to properly stimulate a response. This is where the principle of maximally effective reps comes into play, which we will address in the next article. 

For now, simply remember that we need a high degree of mechanical tension to stimulate hypertrophy and that this can be achieved with heavier loading and/or by intra-set fatigue leading to a lighter load representing a higher relative level of loading/intensity. 

One thing that is worth pointing out here is that there is a difference between external force and intra-muscular tension (mechanical tension). Some movements, such as plyometrics, have a very high force output (Force = mass x acceleration) but do not really stimulate hypertrophy. This is because the rate of movement allows very few actin-myosin cross-bridges to be formed. A low number of cross-bridges means low internal tension within that fiber, which means low internal tension for the muscle. 

To get high mechanical tension, we need two conditions: a high degree of intensity/effort and a reasonably slow movement speed. And no, that doesn’t mean we can just purposefully move slowly during our reps to create higher mechanical tension. While this can help us create a higher degree of intensity with lower weights (which can be useful at times), we still need to get to the point where movement speed slows down DUE TO FATIGUE and not due to us limiting it voluntarily…… 

To boil it down, think of it like this; you need to be pushing your sets to the point where the concentric rep speed slows down significantly. For most, this will start to happen in 3-4 reps from failure, depending on how “fast twitch” you are. Reps performed after this point are the “money reps,” as Arnold would say. If you are not getting to this point with your sets, then you are not really stimulating much (if any) hypertrophy. Furthermore, you simply can not make up for this lack of intensity by doing more volume, as we will discuss below.

Factor 2 – Volume

It was theorized by some that volume was, in fact, the main driver of hypertrophy. On the surface, it makes sense, right? How do you make your muscles grow? You just progressively ask them to do more work. The issue arises here when you scale this up to the long term. 

How does one progressively do more volume throughout their whole lifting “career”? At some point, we would all end up training twice a day for 3 hours each session, 7 days per week. 

Not only is this completely impractical but at some point, it would surely become impossible to recover from such a workload, even if much of it was done at a low intensity. We may grow bigger muscles, but our nervous, immune, and lymphatic systems do not increase in their respective abilities as much as we get jacked. Sure, our training tolerance improves as we adapt to training, but nowhere near enough to support an ever-increasing amount of volume for years on end. 

Not only that, but this also doesn’t explain how so many successful bodybuilders (and other athletes) have had success utilizing lower-volume training. Dorian Yates, Mike Mentzer (before his methods went a bit, you know….), and Lee Haney are good examples of individuals who thrived using a low-volume, high-intensity approach. Then there are all of those who have used programs such as DC training with good effect. 

Now, of course, there’s also a huge number of people who have used a high-volume approach to great success. 

What this tells us is that hypertrophy can be achieved using varying degrees of total volume or workload. This, in turns, means it CAN’T be the main driver of hypertrophy; otherwise, we would see some form of dose-dependent hypertrophy response to training volume. 

A study by Amirthalingam et al. (2017) summed this up nicely by comparing 2 groups, one training using a typical GVT-style routine (10 sets of 10) and the other using half the volume (5 sets of 10). The group running the regular GVT routine (10 sets) got no more hypertrophy than the 5-set group. This shows that, at some point, more volume does not equal more gains. There are plenty of good studies that show this same trend, but this one always springs to mind due to the aura that often surrounds GVT.

So, what role DOES volume play in hypertrophy?

Well, that will also become clearer in the second article of this series, where we dive into the principle of maximally effective reps and how we use that to determine our required volume. But for now, there are two principles we need to know about:

Minimum Effective Volume (MEV) – this is the minimum volume we can do to elicit some form of positive response or adaptation. Performing the minimum effective volume doesn’t get us the maximum stimulus we can from that workout, but it elicits just enough of a positive response that we end up in a net positive once we take into account the catabolic nature of performing a workout and the resources it requires to recover from it.

Maximum Recoverable Volume (MRV) – this is the absolute maximum volume we can perform and still recover. Now, that doesn’t mean to say that we NEED to do this amount of volume to get maximal adaptation from this workout. Always performing the maximal recoverable volume would in fact hinder your progress because you are constantly performing the highest workload possible and leaving yourself little to no “spare” resources to actually grow.

Let’s say we can get the maximum stimulation from a workout using 10-12 sets (taken to the correct intensity). Our MRV may, in fact, be 16 sets. So, if we go with our MRV and always perform 16 sets, then we are performing 4-6 extra sets every workout that we don’t need to. Those extra sets are going to take resources to recover from. 

Remember, protein synthesis is only upregulated in a muscle for around 24 hours after a workout (maybe up to 36 if you’re very lucky in the genetic lottery) before returning to baseline, where there is no net synthesis of new tissue. Now, if you spend pretty much all of those 24 hours just recovering from the work done in the workout, then you leave precious little time to actually grow any new tissue. This is why doing too much volume can be damaging to progress, along with other factors. 

Somewhere in between MEV and MRV lies the mystical beast known as OPTIMAL VOLUME (OV). This is the amount of work we need to perform to get the maximum stimulus from that workout and nothing more. This is where we want to be, as it gives us maximum returns with no wasted output. 

Volume may not be the main driver of hypertrophy, but it IS still an important factor we need to control. There is a minimum threshold of volume that we must perform to achieve the stimulus we desire, and on the other end, there is a limit to how much volume we can perform before we start to get detrimental effects. 

Factor 3 – Muscle Damage 

The idea of muscle damage being the driver of hypertrophy stood for a long time. Once again, it made sense in our heads, so we didn’t argue too much. We train hard, tear up some muscle fibers, then the body’s immune system detects the damage and rebuilds bigger, stronger fibers to protect against it happening again. 

But in reality, this isn’t what happens.

Does muscle damage lead to an increase in protein synthesis? Yes, it absolutely does. But that increase in protein synthesis is only used to repair the existing damage and IS NOT used to create new tissue. Therefore, it doesn’t lead to hypertrophy. 

The problem was that when we first started researching these things we didn’t have great ways of measuring the level of protein synthesis and tracking the end results of it. So, in the labs, we simply saw that muscle damage led to increased synthesis; that was it. We couldn’t see how much the rate of synthesis was raised, where the new proteins were going, and so on. 

Fortunately, now we have much better technology and ways to study these things, and this lack of “super-compensation” became clear very quickly. This also explains why we don’t see any hypertrophy to response in non-training related conditions that create a high degree of muscle damage, such as crush injuries, etc. 

Again, this doesn’t mean that muscle damage is irrelevant when it comes to hypertrophy, however. The reason the idea of muscle damage driving hypertrophy persisted for so long is that many of the things that maximize mechanical tension (the true driver of hypertrophy) also cause larger amounts of muscle damage.

Examples include:

• Emphasizing the eccentric phase
• Loading a muscle in the stretched position
• Large degrees of local muscle fiber fatigue (usually achieved through the volume of work)

So, we are always going to cause at least some degree of muscle damage when we are looking to maximize hypertrophy. Yes, there are methods you can use that cause little to no muscle damage, but we will never maximize hypertrophy by using those alone. 

The problem is that muscle damage imposes a big demand on the immune system to recover from. Meaning we end up in the same situation as we did with volume; we need to find a way of maximally stimulating hypertrophy without causing an excessive amount of muscle damage that is going to take too long to recover from.

This can become even more important if you are an individual who, for whatever reason, has a poor immune system. In this scenario, if you train using methods that cause a lot of muscle damage, then you will often leave yourself in a situation where you won’t progress due to the recovery demands being too great. If you fall into any (or several) of the below categories, then you need to be careful with the amount of muscle damage you cause within your training:

• Naturally poor immune system (get sick regularly compared to others)
• You’re older (50+)
• You’re in a large calorie deficit or have been in some form of deficit for a long time (which partly suppresses the immune system)
• Your general life stress is high (chronically high cortisol suppresses the immune system)
• You have any medical conditions that negatively affect your immune system or metabolism (i.e., hypothyroidism, diabetes)

Putting It All Together

Mechanical tension is the king when it comes to stimulating hypertrophy. If we don’t tick this box during our workouts, then the stimulus we receive is going to be poor at best. This should be the main concern when you are addressing your programming. But that is not the only thing we need to take into account. 

Our volume needs to be dosed carefully so that we are providing enough stimulation to get a hypertrophy response from that workout (MEV) whilst also making sure we don’t go above the amount of work that we can recover from before our window of increased protein synthesis is over (MRV). 

Muscle damage then needs to be taken into account as the amount of damage we cause will directly affect the time taken to recover from the workout and therefore affect our resulting net gains in protein synthesis.

In essence, the perfect workout is one that provides a high degree of mechanical tension to the target muscles using just enough volume to get the maximum possible response while keeping muscle damage to a minimum.

Simple right?.....

How we achieve this is what we will begin to cover in article two.

References

Amirthalingam, Theban; Mavros, Yorgi; Wilson, Guy C.; Clarke, Jillian L.; Mitchell, Lachlan; Hackett, Daniel A.. Effects of a Modified German Volume Training Program on Muscular Hypertrophy and Strength. Journal of Strength and Conditioning Research 31(11):p 3109-3119, November 2017. | DOI: 10.1519/JSC.0000000000001747