A question that comes up with some frequency on forums and message boards, usually from newbie lifters is along the lines of “What is my maximum genetic muscular potential?”

Invariably this leads to a repetitive and pointless argument between those who believe that there are genetic limits to such things as muscular gains and athletic performance and those who believe that anything can be accomplished if you just try hard enough or have the right work ethic.

Now, it should go without saying that nobody can really say upfront what someones genetic potential actually is. Until we live in the world of Gattaca where we can do a full genetic scan and know what it means, nobody can say ahead of time what someone can or can’t achieve. Well, not unless you look at some pretty ludicrous extremes (you’re not going to see someone at 400 pounds ripped any time soon for example).

And, of course, worrying about such things before you even start training is sort of missing the point in my opinion. At a fundamental level, trainees should train and eat properly and let the cards fall where they may. Worrying abut what you might or might not accomplish is putting the cart far before the horse. But that’s another topic for another day. And, of course, doesn’t really answer the question in the title of this article.

I’d note that while I do believe trainees should simply get into proper training and not worry up front what they may or may not accomplish, I also believe that there are genetic limits set by underlying biology (again, modulated by behavioral choices and patterns).

That’s just reality and recognizing them can save people from a lot of mental anguish about what they think they should be able to or could be able to accomplish if they just worked hard enough.

Which is a long way of introducing the topic of today’s article, what is the maximum amount of muscle that someone can gain over a career of proper lifting and nutrition. In looking at the topic I’m going to examine 4 different mathematical models. As you’ll see, they all tend to end up in the same place albeit by slightly different paths.

I’d note that most of what I’m going to talk about applies to male lifters, data on females being much more difficult to come by. Just realize that the average female potential for muscle mass gains is even lower than that in males. I’ll mention some specific below but you can read more about women’s muscular potential in The Women’s Book Vol 1.

The McDonald Model for Genetic Muscular Potential

I’m not sure if I came up with this idea on my own or stole it from somewhere else (probably a combination of the two) but, in a slightly different context (how quickly can someone gain muscle), I have often thrown out the following values for rates of muscle gain.

Again, these values are for males, females would use roughly half of those values. In the first year, a muscular gain of 10-12 lbs might be realistic. This would fall to 5-6 lbs in the second year, 2-3 lbs in the third year and would be minimal beyond that. This would give the average female the potential to gain perhaps 17-21 lbs of total muscle over a career of lifting.

Please note that these are averages and make a few assumptions about proper training and nutrition and such. Age interacts with this as well. Older individuals won’t gain as quickly (with a lower genetic limit) compared to younger individuals who gain more quickly.

As well, age will interact with this; older individuals won’t gain as quickly and younger individuals may gain more quickly.

For example, it’s not unheard of for underweight high school kids to gain muscle very rapidly. But they are usually starting out very underweight and have the natural anabolic steroid cycle called puberty working for them.

Year of training also refers to proper years of training. Someone who has been training poorly for 4 years and gained squat for muscle gains may still have roughly the Year 1 potential when they start training properly.

Now, if you total up those values, you get a gain of roughly 40-50 pounds of total muscle mass over a lifting career although it might take a solid 4+ years of proper training to achieve that. So if you started with 130 pound of lean body mass (say in high school you were 150 pounds with 12% body fat), you might have the potential to reach a level of 170-180 pounds of lean body mass after 4-5 years of proper training. At 12% body fat, that would put you at a weight of 190-200 pounds.

Again, that’s a rough average, you might find some who gain a bit more and some who gain a bit less. And there will be other factors that impact on the above numbers (e.g. age, hormones, etc.).

The Aragon/Helms Model

Another commonly used model was developed by Alan Aragon, Eric Helms or both. It recommends rates of weight gain as a percentage of current body weight for lifters of a different training age. While slightly different than my model above, it ends up at about the same place.

Note: this does not include manipulations such as creatine loading or temporary glycogen supercompensation which can cause rapid changes in “lean body mass” which aren’t actual skeletal muscle mass

So a 150 pound beginner might be able to gain 1.5-2.25 pounds of muscle per month yielding 18-27 lbs per year, nearly identical to my value above.

After a year, he’s an intermediate at 170 pounds and might be capable of gaining 0.85-1.7 lbs per month which yields 10-20 lbs per year. I would personally consider 20 lbs of muscle as an intermediate an incredible response.

After another year, he’s an advanced lifter at 180 and might only gain 0.5-1 lb per month for another 6-12 lbs. Again I would consider 12 pounds to be an incredible response.

So our lifter starting at 150 lbs would top out at 190-200 pounds with 170-180 lbs of lean body mass at 10% bodyfat, essentially identical to my value above.

Once again, women would use roughly half of the above values: 0.5-0.75% for a beginner, 0.25-0.5% for an intermediate and no more than 0.25% for an advanced female. Without boring you with more math, this works out to more or less the same values in my model.

Casey Butt’s Frame Size Model of Genetic Muscular Potential

Of course, both my and Alan’s model for maximum muscle growth are pretty simplified and don’t take into account some of the other factors that can go into determining maximum muscular potential. One that has been argued to impact on overall size and strength gain potential is frame size, usually assessed by wrist and/or ankle size (or other measurements).

Natural bodybuilder and all-around smart guy Casey Butt has done an exhaustive analysis of top level natural bodybuilders and developed a calculator that will predict maximum muscular potential based on height, ankle and wrist size along with goal body fat percentage. He’s also written an extensive, math heavy book showing how he came up with his model.

Casey Butt’s Maximum Muscular Potential Calculator

I’ve run a lifter of different heights with a 7″ wrist and 8.75″ ankle through the calculator to show his predicted body weights (at 10% body fat) and lean body mass.

Of course, variations in ankle and wrist will change the numbers but you can go plug in your own numbers. I’d note that Casey’s calculations end up being a bit more conservative than mine or Alan’s but they are all at least within shooting distance of one another. You’d need to be towards the taller end of things to reach the highest levels suggested by my or Alan’s method.

And while some might argue that frame size has nothing to do with this, there is research to support the idea that it impacts on gains in muscular mass. I’d mention again that Caseys analysis is based on examination of real-world bodybuilders, arguably the group that you’d expect to surpass any supposed limits if it were possible.

At least one study showed that light framed individuals gained less muscle mass compared to heavier framed individuals on the same training program and, at a more basic level, hormones such as testosterone/etc. impact on things like bone growth and frame size. So there is a biologically potential link between frame size and hormone levels that would contribute to trainability and ultimate gains in muscle mass.

It’s also no accident that top strength athletes typically have large frames and robust joints (or that those with relatively smaller frames tend to be drawn/succeed in endurance sports). Some of this is simply so they can handle the level of training needed to succeed at their sport; but some of it is probably indicative of overall hormonal status as well.

The Berkhan Model for Genetic Muscular Potential

Martin Berkhan of Leangains.com has a somewhat simpler model than Casey’s, also based on his observation of top level natural bodybuilding competitors who are contest lean (e.g. 4-5% body fat).

His equation is:

Height in centimeters – 100 = upper limit of weight in kilograms in contest shape.

American readers should take your height in inches and multiply by 2.54, that’s your height in centimeters. Subtract 100 and that’s your predicted maximum weight in contest shape (which is 5% body fat or less for males) in kilograms. Then multiply that value by 2.2 to get pounds. So let’s look at body weight at 5% body fat using the same heights I used for Casey’s calculator. I’ve also calculated out lean body mass at 10% body fat.

While not identical, these values are certainly right in line with Casey’s calculator. I would note that contest lean bodybuilders are often highly dehydrated and may be glycogen depleted and this will tend to lower the measurement of lean body mass. We might realistically add 5-10 pounds of lean body mass to the above values to account for dehydration/etc. With that adjustment, they are more or less identical to Casey’s values.

A Reality Check: Part 1

As I noted in the introduction, a lot of lifters get fairly angry or upset over the above types of estimations, assuming that they don’t take into account individual differences in motivation, work ethic, etc. To that I say nonsense.

Both Casey and Martin’s equations are based on top level natural bodybuilders, the group that you’d expect to surpass such limits if they existed (and who’s dedication and work ethic is pretty hard to question). Mine and Alan’s are based on years of experience in the field. If a massive number of exceptions to the above existed, someone would have seen them by now.

Don’t get me wrong, they certainly exist. As I examined in my series on Fat Free Mass Index, there are the occasional elite bodybuilders or athletes who exceed these levels. But exceptions are just that. Usually these athletes started big and muscular and just got bigger and more muscular. And you aren’t them.

Now I think part of this has to do with exceedingly skewed ideas about what’s achievable, a problem driven by pro-bodybuilding. After seeing a pro-bodybuilder stepping on stage at 260 pounds or more and shredded, the idea that a natural may top out at 180-190 pounds of lean body mass (if that) can be disheartening.

Of course, to the general public, an individual at a lean 180-190 pounds is still pretty enormous. It’s just that compared to the absurd size of a pro bodybuilder, it seems absolutely tiny. But it is reality.

A Reality Check: Part 2

People forget that Arnold Schwarzenegger competed at perhaps 230 pounds (assuming 5% body fat, that’s only 220 pounds of lean body mass) and that was with (admittedly low doses) of anabolic steroids in the mixture.

The simple real-world fact, which can be verified by going to any natural bodybuilding show is that you simply don’t see naturals coming into contest shape much above 200 pounds (the exceptions can usually be counted on one hand) and few even achieve that level of size. It’s always the lighter classes (e.g. 165 lb class) that have the most competitors at natural shows with fewer and fewer coming in at the heavier weights, especially in contest shape.

Now, some guys on stage may weigh more than 200 pounds but they usually aren’t lean enough. At even 10% body fat, a guy at 220 pounds only has 200 pounds of lean body mass. By the time you got him contest lean, he’d likely come in with less than that.

Even when people point to large natural strength athletes who might be 270-280 lbs. natural, by the time you figure in 28-30% body fat, that still puts them right back at a maximum lean body mass of 189-196 lbs. Certainly near the higher end of things but not by that much.

A Reality Check: Part 3

And while many will argue that improvements in training methods and nutrition should change the above values, that simply doesn’t seem to be the case. Human genetics have not changed and you still don’t see natural bodybuilders or other athletes coming in with more lean body mass than would be predicted by the above models. They might get there a bit faster but the overall size of natural bodybuilders doesn’t seem to have changed much, if at all, in decades.

To quote from Casey’s site:

Over the years I’ve also received many emails full of unsubstantiated claims, hostile remarks and even personal attacks because of the information presented here. But in that time, though many have told me they’re easily going to surpass these predictions, I haven’t received any legitimate, verifiable statistics that significantly exceed the results of the equations presented above …including correspondence with some of today’s top-ranked drug-free bodybuilders upon which the equations were partially based.



I anticipate a similar response in the comments section of this article and I’d just refer you to what Casey wrote above.

I’d finish by only saying that I’m not writing this in an attempt to be negative in any way shape or form, as I noted in the introduction, I would rather see people put their energy into their training and nutrition than worrying ahead of time about what they might or might not accomplish. And while I certainly wish that everyone reading this is the lone exception to the values calculated above, well…that’s not what an exception is.

At the same time, a failure to recognize that there are genetic limitations can lead people to do some very silly things in terms of their training or diet. Folks nearing their genetic limits, in an attempt to gain muscle at a rate that simply not achievable will put on enormous amounts of fat in hopes that it will net them a ton of muscle gain. And that just doesn’t ever end up being the case.

I’d only note in closing that the above calculations also has some real-world implications in terms of diet and how much of a calorie surplus is ideal to support muscle growth without generating excessive gains in body fat.

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