By: Eric Trexler
Maximizing muscle mass: Where (and when) you’ll find your genetic limit
The day you begin lifting, you enter yourself into an endless cycle of questions, doubts, and comparisons. Am I making decent progress? Do I need to change my approach? What's actually realistic to expect in the first place? Social media has certainly amplified the doubts. Instead of comparing against the folks in your local gym, you’re seeing people make extraordinary gains everywhere you look – after algorithms filter out the massive number of more typical results, of course.
In the fitness industry, many companies and influencers thrive on these uncertainties. Whether they’re selling you a supplement, a program, a book, a coaching service, or something else entirely, the sales pitch hinges on your doubts: everyone out there is making more (and faster) gains than you, so you need this product (or service) to catch up.
Without understanding what "normal" muscle growth actually looks like, you can't tell whether you're on track or falling behind. You also can’t tell if you’re buying false promises or legitimate expectations.
How much muscle should a beginner expect to gain? When do those gains start to slow down? What do good, bad, or average genetics actually look like in practice? How much does steroid use shift these answers?
These are tough questions to answer without solid data. So, this article aims to give you realistic benchmarks based on actual research data.
Quantifying muscularity
The fat-free mass index (FFMI) gives us a height-adjusted way to quantify and compare muscularity levels. A 180-pound person who's 5'6" is more muscular (relative to their height) than a 180-pound person who's 6'2" at the same body fat. FFMI captures this difference in a single number.
It's not a perfect metric. Fat-free mass includes water, glycogen, and other lean tissue, so a pound of fat-free mass isn’t the same exact thing as a pound of muscle. On top of that, FFMI slightly overestimates muscularity in taller people and slightly underestimates muscularity in shorter people. Nonetheless, it's the best tool we have for these comparisons. You can find FFMI calculators online that do the math for you – just search "FFMI calculator" and plug in your numbers. But the calculation for FFMI is pretty easy to do by hand:
FFMI = fat-free mass / height²
First, you need to estimate your fat-free mass: take your body weight, figure out your body fat percentage (using a scale, calipers, or even a decent visual estimation), and subtract the fat mass from your total body weight. What's left is your fat-free mass. Convert it to kilograms, then divide that by your height (in meters squared), and you’ve got your FFMI.
For example, if you're 5'10" (178 cm) and weigh 180 lbs (82 kg) at 12.5% body fat, you have about 72 kg of fat-free mass. Divide that by your height in meters squared (1.78 × 1.78 = 3.17), and you get an FFMI of about 22.
The FFMI “limit”
Before we talk about typical FFMI values, we should establish some boundaries. Totally untrained males tend to be around 19, whereas females tend to be around 16. Low values (10th percentile) for males and females are 16.8 and 14.4, respectively. But since you’re reading this article, I’m guessing you’re a lot more interested in the upper boundary than the lower boundary.
For years, many believed that a natural (drug-free) lifter couldn't exceed an FFMI of 25. This idea came from a 1995 study that found none of their 74 drug-free gym-goers exceeded 25, while nearly half of steroid users did. In the years since this paper was published, people have started using the FFMI cutoff of 25 as an unofficial "screening test" to identify steroid users.
This is wrong. Or, at the very least, it's a massive oversimplification that somehow became gospel in evidence-based fitness circles.
That study had too small a sample size to define the limits of human potential. Imagine I asked you to figure out the heaviest bench press 1RM a human being could possibly attain. Would you go to your local gym and test 74 people? If not, then you should have major doubts about this universally accepted FFMI limit at 25 for drug-free lifters. Even within that same paper, the researchers noted that many Mr. America winners from 1939-1959 (before steroids were reliably available) had FFMIs above 25 (Table 1).
Some of these bodybuilders, who probably never saw steroids in their life (and certainly wouldn’t have had the ability to reliably implement effective steroid protocols), exceeded 27. These were mostly early-career amateur guys competing in an era with virtually no evidence-based nutrition or training guidelines. Some of these guys were even competing during periods of wartime food rationing – not exactly ideal for a bodybuilding prep. In reality, an FFMI above 25 is certainly impressive, but doesn't represent an absolute ceiling for humanity. If we want to set a more appropriate upper limit, we should take a look at some research on people who are elite at being big.
Real-world FFMI values
College football players
Division I college football players offer great insights for FFMI because these rosters are selected from a massive talent pool and the sport directly rewards size and strength. These athletes also have access to top-tier training and nutrition resources. In other words, we're looking at some of the most genetically gifted athletes in the country, training under optimal conditions with tremendous resources dedicated to their growth.
When I did a study on Division I college football players, nearly a third of them had FFMIs above 25. In the years since, other studies have reinforced those observations. But there was important variation by position (Figure 1). FFMI values of offensive and defensive linemen regularly hit the high 20s, with some reaching the low 30s. These are positions where coaches place considerable emphasis on gaining mass, and also positions where carrying some extra body fat is part of the deal. Meanwhile, wide receivers and defensive backs typically stay in the low 20s because their positions prioritize speed over size.
Sumo wrestlers
If you want to see the highest (presumably natural) FFMIs on the planet, look at elite sumo wrestlers. These athletes often sport FFMIs in the low-to-mid 30s. In order to rise to the highest ranks of sumo, these athletes need to push the boundaries of mass accretion, including both fat-free mass and fat mass. Higher body fat levels tend to be permissive of higher FFMI values, so it makes sense that we’re seeing remarkably high FFMIs in football linemen and sumo wrestlers.
Some skeptics (and cynics) suggest that the values I’ve presented for college football linemen and sumo wrestlers are tainted by unreported steroid use. I’m not naive enough to assert steroid utilization rates of exactly 0% in these populations, but I’m skeptical that steroids are meaningfully distorting these findings. If we’re seeing natural bodybuilders reaching 27-28 with low body fat levels in the 1940s, it’s exceedingly easy to believe that the most elite athletes from sports with massive talent pools and huge financial incentives would be able to reach the 30s – especially with virtutally unlimited support and resources at their disposal. But that raises an interesting question: how do steroids impact our expectations for maximal muscle growth?
Professional bodybuilders and strongmen
With high-dose steroid use and elite genetics, IFBB pro bodybuilders push well into the mid-30s and beyond. In a recent paper, a 6-foot tall, Olympia-qualified pro was measured at 289 lbs and 12% body fat, registering an FFMI of 34. In their primes, notable mass monsters of the IFBB almost certainly reached into the high 30s and even the low 40s, particularly in the offseason when carrying a little extra fat mass. Elite strongmen are no different, with research reporting a group-level average FFMI around roughly 35, with some most likely exceeding that value by a comfortable margin.
Summary: how big you can get
It’s clear that your ceiling for FFMI will be dictated by your genetic predisposition to muscle growth, your training, your nutrition, and the level of body fat you’re carrying. One more (fairly obvious) factor is biological sex.
Women can expect proportionally similar gains to men, but absolute gains are lower because they have less muscle mass to begin with. While a man might have about 65 kg of fat-free mass before they begin training, a woman typically has around 45 kg. This means the same proportional gain looks different in absolute terms. Let’s say a specific year-long program increases FFM by about 1% in men, leading to a gain of 6.5kg. We’d expect women to also increase by around 1% in response to the same program, but that would only constitute an addition of 4.5kg rather than 6.5kg. To see how female athletes stack up in terms of FFMI values, check out Figure 2 which plots data from a huge sample of 372 female collegiate athletes.
In summary, the upper limits for FFMI values differ substantially depending on your circumstances. Table 2 helps you contextualize varying levels of massiveness. You can plug
your current stats into this calculator to find out where you stand.
So, where does your personal genetic limit fall within this table?
There’s only one way to find out: train and eat with the intention of maximizing growth, apply consistent effort over a sufficiently long time scale, make thoughtful adjustments when your gains plateau, and see where you end up.
Reaching your ceiling
We’ve addressed where your ceiling might be, but now we’ve reached another big question: how long will it take to reach your genetic ceiling for muscle growth? Before we answer that, there are a few huge caveats to consider.
First, most people never get there. Any estimate assumes you’re doing everything about as perfectly as possible, consistently, for a very long period of time.
Second, most people train and eat pretty suboptimally when they’re first starting out. They tend to figure it out eventually, but that learning curve can differ dramatically from person to person. This makes timelines unpredictable – training for 5 years provides about 2 years of gains if you spend the first 3 years doing everything wrong. So, any time estimate must once again assume that you’re doing things correctly from day 1.
Third, gains are not linear. They are generally logarithmic, meaning gains tend to slow dramatically over time. But within that broadly logarithmic timeline, every now and then you’ll take some time away from the gym, whether by choice or by circumstance, and regress. On the other hand, you’ll also make a major upgrade to your diet or training every now and then. When this happens, you’ll unlock a surprising little jolt of extra gains, but your rate of growth will eventually slow down again (at a higher level of muscularity).
A great example comes from elite college football players I studied over four years. After years of slow and steady gains, we saw an unexpected surge in Year 4 – likely from new programming, increased motivation as they approached the end of their collegiate career, or both. In any case, the takeaway is clear: you can keep making gains well past your beginner phase, so long as you stay consistent and thoughtfully adjust your approach along the way.
With these factors in mind, we should be asking how long it takes to acquire the lion’s share of the available gains on the table. After that, you’ll probably spend many years making tiny, incremental improvements with periodic spurts of accelerated growth.
If you do everything right from day 1 and continue systematically applying progressive overload, you’re probably going to make the majority of your accessible gains in the first 5 years of training. From years 5 to 10, the annual gains will be slow, but they’ll be measurable over large enough time scales. Gains beyond year 10 are likely to be extremely incremental and sporadic.
I know, I know – you’ve seen a ton of people making gains 20+ years into their lifting career. I have too. Here’s the key: theory versus application. In theory, you’re doing everything perfect from day 1 and you never experience any injuries or setbacks, which makes it hard to believe that substantial gains are occurring after 10 years of grinding. In application, you’re constantly trying out new strategies, improving your approach, and navigating the cyclical surges (and setbacks) that real life throws at us.
Keeping tabs on your growth
Let's talk about realistic muscle gains over a typical 10-12 week training block. That time window isn’t arbitrary – it’s the approximate length of most studies and many training programs. When you’re trying to figure out if a new program or strategy worked for you, you’re probably looking back over the last 10-12 weeks to make that assessment. And if you’re just getting started as a lifter and trying to figure out if your genetics seem better (or worse) than average, the short-term perspective is all you have access to.
A 2020 meta-analysis by Benito and colleagues analyzed changes in fat-free mass across 61 resistance training studies with nearly 1,000 participants. The training programs ranged from 4 to 24 weeks in duration, but they averaged about 10.4 weeks, which is perfect for anchoring our expectations for short-term progress. Figure 3 shows the amount of fat-free mass participants gained over that time frame.
Over 10-12 weeks, the typical increase in fat-free mass was about 1.5 kg (3.3 lbs) of fat-free mass over 12 weeks. You won’t need to totally replace your wardrobe with that magnitude of change, but it’s definitely noticeable, especially if you're taking progress photos and tracking measurements.
Unfortunately, some people just don't gain much muscle, even with consistent training. Low responders only gained around 0.5 kg (1.1 lbs) in the same timeframe. That's frustrating, but it's reality for a portion of the population.
If you suspect that you’re a low responder to resistance training, don’t get too carried away with your pessimism. Recent research shows that being a genuine “non-responder” to resistance training is unlikely. People who initially seem like nonresponders eventually grow when the training dose increases, either through more time on a program or increases in training volume or intensity. Nonetheless, low responders also need to be especially careful about their expectations when assessing short-term progress.
On the flip side, genetic lottery winners – high responders with everything clicking – gained around 3 kg (6.6 lbs) in 12 weeks. These are the people producing transformation photos you see all over social media, causing you to wonder why everyone’s making great gains except for you.
Before we move on, I want to acknowledge your skepticism. About 99% of readers are going to feel like low responders after reading this section. If you’re serious enough about lifting that you found this article and sat down to read it, you probably didn’t gain 3.3 pounds of muscle, let alone 6.6, in the past few months.
This is where context matters. While the study by Benito wasn’t adequately designed to quantify the impact of training status, gains obviously aren’t linear across a full lifting career. We make great gains early in our lifting career, and they taper off hard. If you’re a beginner, these benchmarks are pretty solid. If you’re an intermediate lifter, you probably need to cut them in half, give or take. In other words, your “average” intermediate lifter is probably hoping to gain 3.3 lbs every six months, not every three. If you’re an advanced lifter, you’re probably hoping to gain 3.3 lbs over the course of a year. And, to state the obvious: steroids change the game entirely.
We don’t have a ton of scientific evidence related to steroid use in healthy populations. This is one of those areas where the “in the trenches” knowledge legitimately does outpace the formal research. Nonetheless, the best research available is by Bhasin and colleagues. They gave healthy participants 600 mg/week of testosterone while they lifted weights for 10 weeks. Participants gained roughly 6 kg (~13 lbs) of fat-free mass, which is our best estimate of a “typical” short-term response to steroids combined with lifting.
Short-term benchmarks are great for assessing how well we’re responding to a new program, supplement, or training strategy. But the benchmarks will shift as we become more advanced, which limits their long-term utility. After stacking growth month after month, we end up with plenty of added muscle but very slow gains. When we have the privilege of reaching that point, we need to zoom out and shift our focus back to our FFMI: where we started, how far we’ve come, and how far we believe we can go moving forward.
The bottom line
Understanding realistic muscle gain trajectories isn't about being pessimistic – it's about being strategic. When you know what's actually achievable, you can properly evaluate your ongoing progress. This can help you make realistic assessments of your long-term potential, make better decisions about when it’s time to switch things up, and save you from wasting time, money, and energy on hyped up tools or strategies that are too good to be true.
Most importantly, you can stop worrying about the outlier progress pics you’re seeing on social media. Instead, you can focus your energy on the controllable factors that actually move the needle: consistent progressive training, adequate nutrition, intentional recovery, and the patience to let years of work compound over time. Long-term progress is all about effort, consistency, and targeted adjustments when your progress starts to stall. When you’re armed with realistic expectations, you're much more likely to stay the course and actually reach your genetic ceiling, wherever it may be.
Find more from Eric on…
IG: @trexlerfitness