Maximum Genetic Muscular Potential – The Models And Their Limitations

Key points:

  • There are limitations to the maximum drug-free muscular potential models out there.
  • It’s useful to be aware of them, but you shouldn’t necessarily cap yourself at what these calculators would peg you as being capable of achieving.
  • As fun as it would be, it is not possible to simply make a calculation to determine whether someone is ‘roided to the gills or not.

The guy you see below is legendary Korean bodybuilder, Kim Jin Ho. This photo was taken of him at the Bodypower Pro show in Birmingham in May, a qualifier to get into the Mr Olympia competition 212lb division. Mr Olympia is bodybuilding at the highest level. The contestants are not tested for drug use. He is 5’4, and weighed 178lbs on that day. He won.

Is it possible that he is natural?

Muscular bodybuilding posing bicep flex

Four weeks ago when a mutual friend of ours insisted that he was, I scoffed at this idea. – Certain models of maximum muscular potential would suggest is he is significantly over his genetic limit. And though in fairness they weren’t developed for people of his stature (very short), he’s simply too far over it for him being natural to be plausible. Or is it?

I may now have changed my tune.

Why I’m Writing This Article Now

Ken and I have built our Japanese language sister site,, into the most popular fitness information site in Japan. We are highly trusted, but with such a big readership I feel there is a big burden of responsibility on our shoulders to get things right.

It came to my attention recently that I had screwed up – we released a translation of an article on genetic muscular potential that left people open to steroid accusations as we hadn’t discussed the limitations. In honesty, I wasn’t aware of them until recently but I should have been more careful. We fixed the error a couple of weeks back by providing an extensive update, and influential industry friends here kindly shared the shit out of the updated version once again on social media.

Now, when it comes to my English readers I am guilty of linking far too many people to a couple of articles on genetic muscular potential over the years, believing the formulas and calculations discussed within to be the definitive word on the subject of what a drug-free athlete can achieve.

They are not.

There are some historical exceptions and limitations to the models that I’d like to discuss. And we’ll finish with our man Mr Kim as an example.

Maximum Drug-free Genetic Muscular Potential Models

The Models In Question:

Lyle McDonald has made an excellent analysis of both in his own article on genetic potential and pretty much concludes that when glycogen and water weight are taken into account, that they come out at roughly the same level regarding maximum muscular potential. I’m not going to go into more detail on it, you can read that here.

The Berkhan Model Of Maximum Drug-free Genetic Potential

Though I’d highly recommend that you read the article, Martin’s formula for determining the maximum that a drug-free trainee will weigh when in “stage-shredded” condition (i.e. 5-6% body fat) is as follows:

(Height in centimetres – 98-102) = Body weight in kilos.

This is likely to be the formula that my Facebook chum Gregory O’Gallagher, at the ripe old age of 23, has used to conclude that he is, “pretty close to the brink of what is achievable naturally for my height.“. He really needs to reel his neck in (and trust DEXA scans less) as he’s doing himself a grave injustice here by placing limiting beliefs on himself, which is something I’ll come to later.

Anyway, if you’re,

  • 173cm tall (5’8), your stage-shredded maximum will be ~75kg (165lbs).
  • 178cm tall (5’10) your stage-shredded maximum will be ~80kg (176lbs).
  • 183cm tall (6’0) your stage-shredded maximum will be ~85kg (187lbs).
  • 188cm tall (6’2) your stage-shredded maximum will be ~90kg (198lbs).

While this is not a bad rule of thumb for estimating what a seriously hard-working trainee will achieve over a lifetime, it doesn’t take into account the genetically blessed exceptions to the rule. We’ll look at these exceptions now.

Using FFMI To Determine What Can Be Achieved As A Natural Bodybuilder

Eric Helms wrote an excellent guest article for Alan Aragon’s Research Review recently, What can be achieved as a natural bodybuilder? Alan decided that it was such an important piece that he published it for free, and I’d encourage you to read it. (For those that won’t be bothered, from here to the table graphic below is a quick summary.)

Eric writes about some famous research from 1995, that looked at the fat-free mass index (FFMI) of steroid using and non-steroid using bodybuilders.

FFMI = fat-free mass in kg ÷ (height in meters)²

In the research 83 users, 74 nonusers FFMI were calculated and then compared. The average FFMI of the steroid users was ~25, of non-users it was ~22, and on the extreme ends a handful of non-users reached a FFMI of ~25.

To put that into more meaningful figures, the average height of the men in both groups was ~180cm (5’11), average body-fat percentage ~13%. The average weight of the steroid users was 92kg (202.5lbs), vs the non-users which was 82kg (180.5lbs).

The maximum FFMI of the non-user group was 25; for the steroid-using group it was 32.

From this research, it was suggested that the genetic ceiling for a natural trainee was a FFMI of around 25.

Comparison With The Berkhan Model

Here’s how the Berkhan model looks when the predicted figures from his model are converted to FFMI:

  • 173cm (5’8), 75kg (165lbs) @5% = 71.25kg lean mass = 23.8 FFMI
  • 178cm (5’10), 80kg (176lbs) @5% = 76kg lean mass = 24.0 FFMI
  • 183cm (6’0), 85kg (187lbs) @5% = 80.75kg lean mass = 24.1 FFMI
  • 188cm (6’2), ~90kg (198lbs) @5% = 85.5kg lean mass = 24.2 FFMI

We can see that the Berkhan model figures are lower, and the math works out to be ~6.5-8lbs (~3-3.5kg) lower than a FFMI of 25.

Research vs History

Eric then goes on to talk about the FFMI data of the Mr America winners from 1939-1959, spanning a period where steroids were almost certainly not used, to a time when they were, that was also discussed in that study.

Using Table 2 from Kouri et al, high scepticism is indicated by the winners in the green box, while moderate scepticism is indicated by the winners in the orange box. If we accept the 1939-1944 winners as natural, the average FFMI is 24.9, with the highest reported at 27.3. Applying moderate skepticism and accepting the 1939-1953 winners as natural, the average FFMI is 25.6, with the highest reported at 28.0. These means are not much different from the 1939-1959 group mean. In fact, the authors analysed the FFMI’s to determine if they were increasing over time. They noted: “there was no significant trend towards increased FFMI among the Mr. America winners over a 20-year span from 1939 to 1959.” Thus if drug use was occurring, perhaps it wasn’t frequent or effective enough to significantly affect the aggregate FFMI.

Mr America Winner FFMIs - 1939-1959

One thing worth mentioning, as it’s an issue I’m sure people will raise: ‘golden age’ bodybuilders usually carried more fat on stage than guys today (8-10% was more common than the 5-6% we expect now) which means their FFMIs were overstated a bit. On the flip side, awesome leg development wasn’t expected or desirable (compare Arnold’s legs to literally any pro BB today), which probably more than makes up for the difference. (i.e. if those guys were competing today, they’d probably have 3-4kg (~7-9lb) less fat, but at least 3-4kg more muscle on their legs and ass.)

Criticisms of the 25 FFMI Genetic Ceiling

1) There were guys with a FFMI over 25 that were almost certainly not on steroids. You can see from the table, one guy had a FFMI of 27.3, and another with a FFMI of 26.9, and if we lower our scepticism just a bit, we can take it all the way up to 28.

2) If we’re going to take a FFMI of 25 (or even 27.3 or 28) as the absolute limit of what’s attainable naturally, we would also have to assume that the most genetically elite people imaginable are included in that sample, which is not likely. Yes, those guys had physiques that were on par with the top drug-tested bodybuilders today (and some lifters of that era, including 26.9 FFMI Grimek, put up weights that are still very impressive by today’s standards), but lifting and physique sports have grown considerably since the ’40s and ’50s.

There is certainly the possibility that there are some people better suited for gaining muscle mass currently participating in bodybuilding and strength sports now, unless we can be sure that the bodybuilders from the ’30s and ’40s represent the absolute pinnacle of attainable human muscularity. However, the records in every other sport have progressed over time as better genetic specimens have entered the pool of competitors (I’d suggest The Sports Gene by David Epstein for more information), so I’m not sure why we’d assume levels of muscularity in drug-free bodybuilding would be any different.

3) We also have to assume that we’ve made no progress whatsoever in terms of training, nutrition, and supplementation. The cynic in me believes that we really haven’t made that much progress in terms of training for hypertrophy since a) periodization doesn’t seem to play much of a role, and b) the biggest determining factor for muscle growth just seems to be training hard and doing a bunch of hard sets, with other factors playing a much smaller role. Basically, getting big isn’t rocket science – it’s mostly about hard work.

However, I do think we’ve made some progress in terms of nutrition and supplementation. I mean, take something as basic as creatine – those guys didn’t have access to it unless they were eating a lot of raw red meat. Will it make a night-and-day difference? No. But it has been shown to pretty reliably help people gain a little more muscle mass.

Applying the Formula – An Example Case

Kim Jun Ho - Bodypower Pro 2015 Lineup - iPhone Snap


So let’s go back to Mr Kim Jin Ho. He was on stage at 178lbs (~81kg), ~5’4 (163cm) in height.

  • This puts him with a FFMI of 29.5, with an adjusted (for height) FFMI of 28.4, which is just 1.1 points above the biggest of the Mr America Winners of the 1939-1944 (almost certainly steroid-free) period.
  • He is 46, so he has a very long training history, and many years to potentially put on muscle.
  • He had a normal voice, his jaw/forehead looked normal, and he doesn’t have the distended gut. (So, no hallmarks of human growth hormone use.)
  • Shredded, but didn’t have the overpowering traps/delts, and no acne marks on his back. (So, none of those obvious signs of AAS use.)

So is he natural?

Well, I wouldn’t bet my life savings on it, but it’s certainly possible. Regardless, this misses the point of this article…

The Point Of The Article

It’s essential to keep these models and their limitations in mind when you plan your bulk. This helps to ground us in reality rather than fantasy land, ensuring that we don’t fall into the ‘dream bulk’ trap, gain a ton of fat, and waste a lot of time and effort dieting it off again.

The Casey Butt / Berkhan model calculations are probably best described as roughly an average of what’s attainable for most reasonably “blessed” people.

A FFMI of 25 is the number usually thrown around as the upper limit, even for someone with great genetics. But as we’ve seen, there are people who go beyond that.

We know that a FFMI of at least 27.3 is attainable naturally, and in all likelihood, 28.0. Add in some minor advancements in training, nutrition, and supplementation, along with some scepticism about whether the most elite of the elite genetically were competing in bodybuilding in the ’40s, and I think it’s pretty likely that some people can attain a FFMI in the 28s naturally. Can many people? Absolutely not. Can most people reach the more conservative limit of 25? Nope. Your genetics are your genetics, and some people were simply dealt a better hand than others. But a FFMI over 25 definitely doesn’t automatically mean someone’s using drugs. And if you have rocketed your way up to the genetic limits calculated by the Berkhan model in your first few years of training, there’s every reason to believe you are one of the few that has the potential to go on and exceed it.

So, don’t limit yourself based on these formulas. The mind exerts a powerful effect over the body. Believe in yourself and have the mindset that you can, and you may just do so.

Update 30th Sept. 2015: Here’s an excellent article by Greg Nuckols over on on how to calculate YOUR Drug-Free Muscle and Strength Potential.


Thank you for reading. 

Productive discussion, correcting errors in my logic, etc. are welcomed in the comments. Accusations or name calling are not, and will be deleted without hesitation. I just can’t be bothered with it.

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Andy Morgan

I am the founder of, this is my sincere effort to build the best nutrition and training guides on the internet. Some readers hire me to coach them, which I've been doing online, via email, for the last seven years. If you're interested in individualized, one-on-one nutrition and training coaching to help you crush your physique goals, let's start the conversation.