Finding Your Genetic Muscular Potential

I often come across questions on fitness forums from beginning bodybuilders wanting to know what their maximum genetic muscular potential is. The responses to this question often fall into one of two categories:

  • Those who think a limit exists, over which it is impossible to gain more muscle.
  • Those who think there is no limit, and that with proper nutrition and training, anything is possible

It goes without saying that no one really has the answer to this question, for it is impossible to know what everyone can accomplish with his/her body. As a beginner, preoccupying oneself with this is pointless. Athletes should simply train and nourish themselves correctly, which will undoubtedly give them results. Wondering what the maximum you can accomplish is before having started to accomplish anything is putting the cart before the horse.

horse cart

I personally believe there is a limit, but that athletes should focus all of their attention on their training rather than worrying about this. The limit is a genetic one that the metabolism imposes on itself (which is of course, also impacted by the athletes choices). Understanding this concept can help you avoid over-complicating things or spending too much time mulling over what your chances of accomplishing certain objectives are.

But how to determine, quantify and qualify this limit? How much muscle mass can a person gain over the course of their life, assuming diet and training are on par? I will present several models, but you will notice that at the end of the day their results are all quite similar. These models apply to male athletes. For female athletes, genetic muscular potential is more difficult to determine, but one thing is certain: it will always be inferior to that of males.

The Alan Aragon Model

This model carries the name of a reference in the subject. In one of his publications, he proposes a different approach to that of McDonald, but the results are quite similar. He gives an estimation of the quantity of muscle that is possible to gain. This model does not take into account creatine cycles or glycogen overloading, activities that could rapidly cause muscle composition to vary (without changing the quantity of skeletal muscle.)

  • For a beginner, gains corresponding to between 1-1.5 % of total weight.
  • For an intermediate athlete, gains between 0.5-1 % of total weight.
  • For an advanced athlete, gains between 0.25-0.5 % of total weight.

For a beginner at 60 kg, it will then be possible to finish the year at 69 kg at the same body fat. After a year, the beginner is then intermediate, and able to end his 2nd year at around 76 kg and so on… (in reality, body fat will diminish for many over these same years, so results may not be exactly as presented in my example which supposes an unchanging level of body fat.)

If we compare the McDonald and Aragon models, we find pretty much the same results.

The Lyle McDonald Model

Carrying the nutritionist’s name, yet another expert, the McDonald model is based on his own experience. Here are the values he proposes:

  • Within the first year of training, between 10 and 12 kg of gains (1 kg per month).
  • Within year 2 of training, between 5 and 7 kg (500g per month)
  • Within year 3 of training, between 2 and 4 kg (250g a month)
  • Within year 4 of training, between 1 and 2 kg.

These observations are made for male athletes. For females, these values should globally be halved.

Furthermore, it is important to understand that age will influence the speed at which it will be possible to gain this mass. For an older individual, it will take much longer than for an adolescent who is full of anabolising hormones (puberty!). Also, these numbers suppose, of course, that the subject is working out and follows an adapted diet; a person who has not been regular with his training for 4 years will have pretty much the same gains as a beginner who worked out regularly for a year.

If we calculate using the higher averages, it will be possible for you to gain over 23 kg of mass in 4 years. If you started with 25% body fat for 80 kg, you could potentially reach 72 kg with 8% body fat after 4 years of training. Of course, these are averages and a lot of factors must be taken into account. Some will gain more muscle mass, some less (age, hormonal disposition, genetics…these are all factors that may impact results).

The Casey Butt model

This model is slightly different than the other two, because it takes into account one’s bone mass. Certain nutritionists and trainers think that morphology is a non-negligible factor when determining muscular potential.

Casey Butt did a detailed analysis on the evolution of muscle mass in a group of bodybuilders, and developed a calculator which uses height and the circumference of ankles and wrists, as well as body fat.

For those of you who are curious, he justifies his analysis in a book you can find here.

Here is Cassey Butt’s calculator online.

After a few tries, C. Butt’s model is a bit more modest than that of Aragon and McDonald, but results still remain pretty similar.

Although some still think that bone circumference doesn’t affect genetic potential, researches seem to support this idea. Furthermore, Casey has worked with the elite of bodybuilding, a group we can always amuse ourselves trying to surpass 🙂

At least one study has proven that individuals with smaller bone structures put on less muscle mass than individuals with larger ones, with the same training and diet. Furthermore, hormones such as testosterone influence bone growth and density. This allows us to confirm that there is at least a potential link between bone structure and the hormones that contribute to muscle gains.

It is also not a coincidence that most elite bodybuilders often have denser bone structures and resistant ligaments. Those are are thinner generally are more skilled at endurance sports. We can see this in another way: these two types of people are respectively “pre-disposed” to succeed in their sport.

The Martin Berkhan model

Martin Berkhan, a coach who popularized intermittent fasting, proposes a model that is similar to that of C. Butt all while being simplified. The model is based on observations Berkhan made while coaching competitive bodybuilders (between 4-5% body fat).

His equation is as follows:

  • Height in centimeters-100 = upper limit in kg to be in shape for a competition (4-5% body fat).

Lets take an athlete at 10% BF as an example:

  • Assuming a height of 172 centimeters, we end up with a weight of 72 kg at 5% bf, and a weight of 77 kg at 10% bf.  This corresponds to around 69 kg of lean mass.
  • Assuming a height of 177 cm, we end up with a weight of 77 kg at 5% bf, and a weight of 81 kg at 10% bf. This corresponds to around 73 kg of lean mass.
  • Assuming a height of 182 cm, we end up with a weight of 82 kg at 5% bf, and a weight of 87 kg at 10% bf. This corresponds to around 78 kg of lean mass.

Take your height in centimeters, and subtract 100 cm. You will then have your genetic muscular potential in kg. These results are more or less equal to those of C. Butt. A competing bodybuilder’s weight on stage is one that takes into account high levels of dehydration and low levels of glycogen. By adding between 3-5 kg of water, we end up with the same numbers as C. Butt.


As mentioned in the introduction, many may become frustrated by the numbers they will get. Nevertheless, keep in mind that all of these models have one thing in common: they are based on the observation of elite athletes; for these people, motivation and dedication towards their sport has already reached a level that most of us realistically won’t ever achieve.


Aragon and McDonald’s models are based on years of observations; if there were exceptions to their results, they would have already noticed them.

One possible source of frustration simply comes from seeing an athlete on stage at 110 kg at 4% body fat, all while knowing that a dedicated athlete could only ever achieve 86-87 kg naturally. Understand though: for most, 87 kg with 4-5% body fat is already a huge accomplishment. Compared to the physique of a bodybuilder, it may seem ridiculous, but this is reality.

Some believe that by changing training routines and having a specific diet (Eating 4-6 grams of protein per kg for example) it is possible to surpass these limits, but this doesn’t seem to be the case. Over the years, natural bodybuilders have not gotten stronger, the values have remained the same. Although recent discoveries in nutrition have led to quicker muscular development, the weight and size of bodybuilders have not changed for decades. Some think that accumulating a high amount of fat during a bulk will allow them to maximize lean gains, however this is unfortunately not the case.

In conclusion, I would say: take this article as a piece of advice; it makes more sense to seriously apply yourself to your training and diet rather than to have a distorted vision of what you can possibly accomplish naturally 🙂


  1. Martin Berkhan – What’s My Genetic Muscular Potential?
  2. Lyle McDonald – What’s My Genetic Muscular Potential?
  3. Casey Butt – Your Maximum Muscular Bodyweight and Measurements
  4. Marc Perry – How Much Muscle Can You Gain Naturally?

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