Your Guide to Training Volume Article Series: Chapter 2 – The Principle of Maximum Effective Reps

Your Guide to Training Volume Article Series: Chapter 2 – The Principle of Maximum Effective Reps - 1st Detachment

Guest article written by Tom Sheppard of Phoenix Performance Training.

We meet again, avid reader.

Welcome to Chapter 2 of this article series on training volume about hypertrophy. In Chapter 1, we covered the main factors that stimulate hypertrophy. After all, we can’t talk about how to train for hypertrophy without knowing what causes it. Now the geeky stuff is out of the way; we can start to get into the more interesting and applicable material. 

Knowing how much training volume to do is a difficult thing to decipher. After all, you have successful training programs that use a wide variety of volume prescriptions, and lifters have built incredible physiques using both extremes. So how much should YOU do? 

There will be a lot of different factors that play into this, including:

  • Training age,
  • Natural recovery ability,
  • The intensity to which you push your sets
  • Training “sensitivity”
  • Diet status (surplus or deficit) 

The most common problem that we see is, trainees that are performing too much volume at too low of an intensity level to stimulate the progress that they want. You can not compensate for lack of intensity by doing more work; it doesn’t work like that. 

This article will illustrate why that is the case and give you a blueprint to help estimate how much training volume you need to perform and at what intensity to keep progressing.


The Principle of Maximally Effective Reps

We briefly touched on Maximally Effective Reps (MERs) in the first article. MERs are reps that stimulate all possible motor units and muscle fibers, including the fast twitch fibers. This is achieved by performing a rep that requires at least 80% of your maximal force available at that moment (there’s some variation with that figure, but it’s a solid baseline). So, for example, if we performed a set of squats and had 80% of our 1-rep max on the bar, all our reps would be maximally effective because the load would dictate that we need 80% of our maximal effort right from rep one. 

Remember, the fast-twitch fibers are the ones that have the growth potential. Slow twitch fibers have little to no growth potential, so stimulating them doesn’t get us any hypertrophy. But our body likes to be efficient and will only recruit the fibers that it MUST complete the task at hand. 

So, to start, it will recruit just some of the slow twitch fibers. If that doesn’t produce enough force, it will progressively recruit more and more slow-twitch fibers. If that doesn’t produce the required force output, it will recruit the intermediate fibers (which still have minimal growth potential). If this doesn’t result in enough force output, that is when the fast twitch fibers will get recruited. 

This is why a high degree of mechanical tension is needed for growth because it means we have created a situation where the body must recruit all the fast-twitch fibers to get the job done. 

However, starting with a heavy load is not the only way to achieve MERs. As discussed in the previous article, muscle fibers will fatigue at around 3-4% per rep (variation here is based on the fast/slow twitch you are). So even a lighter load will eventually represent an 80%+ effort and cause full fiber recruitment. Table 1 (below) from the previous article sums this up nicely. 

Rep Number

Relative Load/Intensity (%)

Degree of Fatigue (%)


































12 - Failure




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%

As we can see, if we start with a load that is 60% of our 1-rep max then the first five reps are not MERs as they do not represent a high enough relative load to get maximal recruitment. However, from rep six onwards, the load now represents 80%+ of our max force output (at that time), allowing us to start getting maximal recruitment. 

So, the only difference between using 60% and 80% as your starting load is that if you use 60%, you must perform five initial reps before achieving MERs. Whereas, with 80% you have that from the start. This is an important point, which we will touch on later.

What we can infer from Table 1 because the maximum number of MERs we can get from a set is six if we push to the point of completing the maximum number of FULL reps possible. If we push to the point where we fail a rep due to fatigue, then we could argue that we are achieving seven MERs, even though the rep isn’t completed, but I’ll let you debate that. 

So, the intensiveness of the set, or if you prefer, how close it is pushed to failure, determines how many MERs we get from that set (see Table 2 below).

Reps In Reserve (RIR)

Number of MERs achieved


7 (possibly)

0 (can’t complete another full rep)














Table 2 – The relationship between how close to failure a set is pushed (known as reps in reserve/RIR) and how many maximally effective reps are achieved.

Why it is Quality > Quantity

Now you can understand the statement I made in the introduction of this article “You cannot make up for a lack of intensity by simply doing more work, it doesn’t work like that.”. 

If a person is not pushing their sets to a high enough difficulty level, then they may be getting ZERO MERs per set. In that scenario it doesn’t matter how many sets you do because zero multiplied by one million still gives you zero. Of course, this is an extreme example, but you get the picture. 

What we usually see is lifters thinking they are pushing to one or two reps in reserve (RIR) when in fact they have more like four or five RIR. 

Why is this important? Because this is going to radically change the number of MERs the lifter achieves. If we look at this difference across the course of a whole workout consisting of 10 sets:


Lifter 1 is working at an intensity of 4-5 RIR = 1-2 MERs x 10 sets = 10-20 MERs

Lifter 2 is working at an intensity of 1-2 RIR = 4-5 MERs x 10 sets = 40-50 MERs


Now, both lifters have performed the same volume, but Lifter 2 has achieved two to five times more MERs than Lifter 1. This is an enormous gulf in terms of workout efficacy and the stimulus that will be achieved from the workout. 

The inevitable follow up question will then be…

“But can’t Lifter 1 just do more volume to make up for this difference in stimulation?”

Sure, but Lifter 2 would need to perform two to five times more volume to match the stimulation achieved by Lifter 1. Meaning Lifter 2 would end up performing anywhere from 20 to 50 sets to achieve the same stimulus! 

Now, even if Lifter 2 was willing and able to do this amount of volume that still wouldn’t mean they would get the same positive outcome from the workout. Doing more work means releasing more cortisol/adrenaline (neurological fatigue) and means expending more energy to perform the work.

There is only so much work you can recover from and if you exceed that then you make no progress, even if you do accumulate enough MERs. Remember, you only get elevated protein synthesis in a muscle for 24-36 hours. If you spend that entire timeframe recovering from the excessive workload you did, then you end up with zero net muscle gain. So, Lifter 1 would most likely perform all that work and still get no benefit from it. 

Whether you like it or not, at some point if you want to make progress then your sets must be HARD. There just isn’t a way to work around that fact. 


How Many MERs Do I Need to Grow?

So now we move on to the information you’ve all being dying to know since the start of the first article…

 “Bro, just tell me how much lifting I have to do to get jacked.”.

We’re getting there I promise. But just like the hot girl (or guy) you want to hook up with; if I just gave you the good stuff right away then you wouldn’t respect me afterwards. 

As I mentioned earlier, there are several factors that will affect exactly how many MERs you need to achieve maximal growth. But I will outline some general guidelines below based on training experience.


Beginner – 8-15 MERs per muscle group per week

It can be very hard to classify people based on training age. I know plenty of people who have been training for years but are still beginners. Likewise, I’ve met others who have progressed passed the beginner stage in 9-12 months easily by working hard, following the right program, and doing everything right outside of the gym (being dealt a good hand in the genetic lottery also helps here). 

When we talk about beginners, we are talking about people who are still making “newbie” gains. They are gaining muscle at a fast rate, can make linear progression in terms of their strength, and probably don’t have to be paying that much attention to the other stuff (nutrition, sleep etc.) to do this. This is because their training sensitivity is very high due to it still being a novel stimulus to them. 

This category would also include anyone who has taken a lengthy break from training because their sensitivity to training would once again be very high. This is why programmed de-loads can be very useful; but we’ll talk about that in the third article.

Studies on un-trained populations have found that programs that result in as little as 8-10 MERs per muscle group per week can be very effective for hypertrophy. If you’re not completely un-trained then this is likely going to be a little low as you will have at least some adaptation to the training stimulus. 

Hence my suggested range of 8-15 MERs per muscle group per week

This means that if you can train your work sets to an intensiveness of 1-2 RIR (RPE 8-9) then you can maximize your progress in terms of hypertrophy from as little as two to four work sets per week per muscle group (enjoy that while you can). 

The caveat here is that beginners will often find it difficult to push to a genuine RPE 8 or 9. This is because their motor skills (proprioception, intra and inter-muscular coordination) will generally be poorly developed. This means that they often must end sets not because they cannot create the muscular force required but because they cannot stabilize or control the movement any longer. 

If this is you, or someone you coach, then you can navigate around this by sticking to machine or cable-based movements that require considerably less stabilization, which will allow them to push to a genuine RPE 8 or 9. Or your other option would be to do an extra set for each muscle group to account for the fact that their RPE 9 is probably more like an RPE 8 from a muscular effort standpoint. 


Intermediate – 15-25 MERs per muscle group per week

It is easier to classify an intermediate in my opinion. Intermediates are lifters/athletes who are passed the stage of making incremental progress on a short-term basis. In terms of strength, this refers to people who will now require a structured training cycle (usually around 10-16 weeks) to hit solid PRs in their lifts. But they are still hitting PRs reliably at the end of each cycle. 

In terms of hypertrophy this is an individual who’s rate of muscle gain has now slowed down to a more sustainable level. An intermediate training for hypertrophy can expect to put on around 1-1.25lb of muscle tissue per month if they do everything right. Can some people gain more? Sure, those who are genetically predisposed to putting on muscle easily can gain more than this. But for a drug-free trainee if you manage to add 12-15lbs of muscle in a year then you are progressing extremely well. Most will fall well short of this.

Remember, we’re talking 12-15lbs of MUSCLE TISSUE here, this would equate to around 20-25lbs of scale weight increase when you take in to account the extra water, glycogen and fat that will come with it. People really under-estimate what 15lbs (for example) of actual muscle tissue does to a person’s appearance. If someone hasn’t seen you for a year and you’ve gained that much muscle, you will look like a different person to them. Likewise, if a competitive bodybuilder steps on stage 15lbs heavier than their last show (in the same condition) people would be shocked. 

Now obviously as an intermediate you are going to be more adapted to the training stimulus. Gone are the days of not being able to walk for five days after your squat workout (or, at least, they really should be). So, we will now need a greater stimulus to get the response that we want. 

For intermediates my suggested range is 15-25 MERs per muscle group per week

It would be uncommon for an intermediate to genuinely need 25 MERs/week. This would generally be reserved for individuals who have historically trained using high volume approaches. Remember, your body will adapt to whatever workload you give it over time. So, if you consistently train using a higher volume than is necessary then at some point it will acclimatize, and you will get no stimulus from it. Again, this is why the next article will cover the use of de-loads to re-establish training sensitivity. 


Advanced – 18-30 MERs per muscle group per week

Advanced trainees are in a scenario where they must fight tooth and nail for every bit of progress. For a strength athlete they will only be capable of hitting PRs on their main lifts likely once or twice per year because it will take months of strategic planning to get them up to that level. Even then sometimes they won’t improve on their previous result if the training cycle didn’t go to plan for whatever reason. 

For those chasing hypertrophy we’re looking at gaining 3-5lbs of muscle tissue per year. Remember that will mean about 5-8lbs of scale weight gain and this is presuming you are doing everything possible to maximize your ability to grow muscle (short of taking PEDs). 

The volume requirement for some advanced trainees won’t increase that much. The reason for this is that advanced trainees are going to be more efficient at recruiting their fast-twitch fibers. This allows them to start stimulating MERs earlier and fatigue them more quickly. This is most prominent in strength athletes but will also be present in those who train primarily hypertrophy also (more so who train in the lower rep ranges). This increased efficiency helps to off-set some of the adaptation to training resulting in a lower increase in required MERs. 

In fact, this is why many advanced athletes (primarily strength) find they have to train LESS than when they were intermediates. Five sets of five at 80% of 1 rep-max is perfectly acceptable for intermediates and may well be too easy for a beginner, but it would floor an advanced athlete, if they could even complete it. 

With that in mind my suggested range for advanced athletes is 18-30 MERs per muscle group per week.

Again, it would be rare for individuals to need 30 MERs per week to progress, but if you are right at the top of your genetic ceiling in terms of hypertrophy then this may well be the case. 

As you become more advanced not only do you need to do a bit more volume, but you will also be fatiguing your nervous system to a greater degree, through more efficient recruitment as well as the fact you will likely being using heavier training loads. This increased recovery demand is where intensification methods such as rest-pauses, drop-sets etc. can become incredibly useful to help achieve the required MERs using less total workload. 

Hopefully this second article has given you a better grasp of the principle of Maximally Effective Reps and how it governs how much volume you need to perform, and at what intensity, in your training. The third article in this series will be about how to maximize the efficiency of your training using de-loads and intensification methods. Until next time.

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