Introduction
I was watching Greg Doucette on YouTube the other day, and for what feels like the millionth time, he was claiming his “elite level genetics” explain his success in bodybuilding, casually brushing off the impact of steroids like they were just a sprinkle of seasoning on his gains. And every time, I want to reach through the screen and scream, “Yeah, elite level genetics for responding to high doses of steroids, you cookbook-cooking cooksucker!” But it got me thinking—what’s the real secret behind bodybuilding success? Is it really just about having good natural muscle-building genetics, or could it be more about how well your body responds to steroids and other PEDs? Let’s dive into that question and see if we can figure out what separates the best from the rest.
Section 1: The Basics of Genetics in Muscle Growth
Genetics are foundational in determining your muscle growth potential, but let’s clarify what that really means. You’ve got genes like ACTN3, which is linked to whether you have more fast-twitch or slow-twitch muscle fibers. Fast-twitch fibers are crucial for explosive strength and hypertrophy—the kind of muscles that can win you bodybuilding titles.
Then there’s the MSTN gene, which produces myostatin, a protein that puts the brakes on muscle growth. Some rare folks have mutations in this gene, leading to significantly higher muscle mass—kind of like having the muscle-building equivalent of a green light all the time. But before you go asking your doctor to test your myostatin levels, let’s be clear: these mutations are rare and not something you’re likely to have unless your family tree includes a Belgian Blue cow.
And let’s not forget IGF-1 (Insulin-like Growth Factor 1). The IGF1 gene produces this hormone—yep, the gene and hormone share the same name—and it’s essential for muscle repair and growth. IGF-1 promotes the proliferation and differentiation of satellite cells, which help repair muscle, and enhances protein synthesis. So if you’re like me and tend to confuse these names easily, just remember: the gene makes the hormone, and both are critical in muscle growth.
Also, if you’re wondering why your girlfriend seems to have more muscle size and definition than you despite skipping the gym while you’re in there every day, well, genetics might be playing tricks on you. Or maybe she’s sneaking in a few cycles of anabolics herself! Yeah, that’s probably it, bro. Speaking of your girlfriend, let’s talk about people who don’t even seem to need the gym to look jacked…
Section 2: Muscle Without Training: The Genetics Behind Natural Muscularity
Some people seem to maintain muscle mass effortlessly while the rest of us grind away at the gym. What’s going on there? It could be a few things, starting with myostatin. Individuals with lower levels of this protein, due to rare genetic mutations, are predisposed to more muscle mass even with little to no training. But again, this is a rare genetic anomaly—so don’t assume that your lack of biceps is just because you’ve got too much myostatin holding you back.
Another key factor is basal metabolic rate (BMR). People with a higher BMR burn more calories even at rest, which supports muscle maintenance by ensuring a steady supply of energy for basic physiological functions, like protein synthesis. Plus, it’s easier for them to stay lean, which means their muscles look more defined.
Hormonal levels are another piece of the puzzle. If someone naturally has higher testosterone or growth hormone levels, they might be more muscular without much effort. Combine that with favorable muscle fiber composition—more Type II fast-twitch fibers—and you’ve got a person who’s naturally more jacked.
This brings me to a little story about my son. He’s only 7 years old, and already he’s showing pretty impressive muscle development. Now, most people might assume he gets his muscularity from me, but the truth is, he looks a lot more like his mother—lucky kid! His body shape and muscle bellies resemble hers far more than mine. My wife doesn’t work out all that often, but I’ve always thought that with her long muscle bellies and favorable muscle insertions, she has more bodybuilding potential than I do—but don’t tell her that! I’m no blimmin’ simp, after all.
It was actually my intention all along to produce a superhuman kid when I first laid eyes on her. I was thinking to myself, “If only there were some technology that could somehow produce a kid with half my DNA and half of hers…” Well, after some careful “experimentation,” science hasn’t let me down yet!
Let’s also give a nod to bone structure, muscle attachment points, and muscle belly length, which can create an illusion of greater muscle size even if there isn’t that much muscle mass. Longer muscle bellies generally look fuller and can contribute to a more aesthetic physique, but they also might have functional implications depending on the muscle group. So, if your girlfriend looks more swole than you, relax—it might just be her bone structure and muscle insertions fooling you. You still wear the pants in the relationship… at least figuratively. I mean, we all know who’s the “alpha” here, right? (Hint: it’s probably not you, bro, but hey, no judgment.)
Section 3: Genetics and Response to Training Stimulus
We’ve all been there: you and your buddy start the same workout routine, but while he’s blowing up like a human air pump, you’re still stuck on scrawny mode. Why is that? Genetics again. People with a higher proportion of fast-twitch muscle fibers (Type II) tend to respond better to resistance training, especially when it comes to hypertrophy and strength gains.
Muscle tension is one of the largest contributors to hypertrophy, and this is where neuromuscular efficiency comes in. Some people are just wired to recruit more muscle fibers per rep, creating more tension in the muscle and driving growth more effectively. In other words, their muscles are working smarter, not harder.
And let’s not forget about satellite cells, the unsung heroes of muscle growth. These are a type of stem cell that resides between the muscle fibers and their surrounding sheath. When you train, satellite cells get activated, multiply, and fuse with existing muscle fibers, helping to repair and grow them. If your genetics give you a higher count or more active satellite cells, you’ll recover faster and build muscle more efficiently than someone who has fewer of these cells.
Section 4: Steroid Responsiveness and Genetics
Here’s where the rubber meets the road for a lot of top-level bodybuilders: steroid responsiveness. It’s not just about how much juice you take; it’s about how your body processes it. Genetics play a huge role here.
First, let’s talk about androgen receptor sensitivity. These receptors in your muscle cells are what steroids bind to, sparking the muscle-building process. If you’ve got more androgen receptors or more sensitive ones, you’re likely to get more out of the same dose of steroids than the next guy—at least in theory. Now, let’s discuss how differences in the androgen receptor (AR) gene might influence steroid responsiveness. While there’s some research hinting at a connection—basically suggesting that certain variations in this gene could make you react differently to steroids—it’s important not to get ahead of ourselves. The science is intriguing but not definitive. Studies suggest a potential link, but we’re still in the ‘this could be a thing’ phase rather than ‘this is definitely a thing.’ So, while it’s tempting to believe your genetic makeup could make you a steroid super-responder, take it with a grain of salt. It’s a fascinating area of study, though, and one to keep an eye on as more research rolls in. Personally, I’m certain that some people are more responsive to steroids than others, but I’m just not certain what the exact mechanism behind this is.
Then there’s steroid metabolism. Some people’s bodies are better at processing and utilizing steroids. Enzymes like CYP3A4 affect how quickly steroids are broken down, which can influence how long the effects last and how powerful they are. Combine this with factors like hormone-binding globulins—which determine how much free testosterone or synthetic androgen is available in your system—and you’ve got a whole cocktail of genetic influences that determine how well you respond to steroids.
Plus, some people can take higher doses without experiencing significant side effects, another aspect influenced by genetics. The ability to metabolize steroids efficiently without adverse effects can be a game-changer at the elite level.
And if you’re wondering about clenbuterol, some argue it’s not just for fat loss but might have anabolic properties too. Though the evidence is still up for debate, your genetic makeup could determine how your body reacts to it, both in terms of fat loss and potential muscle gains. I once read that clenbuterol’s mechanism might involve beta-3 receptors, which are more prominent in animals but not confirmed in humans. This might explain why its effects are more pronounced in some animals compared to humans.
Section 5: Other PEDs and Genetic Responses
Steroids aren’t the only PEDs that can give you a leg up (or a bicep boost). Insulin, growth hormone (GH), SARMs, and even creatine are influenced by genetics. For example, genetics can affect insulin sensitivity, which in turn influences muscle growth. Some people can use insulin more effectively to shuttle nutrients into muscle cells, promoting growth and recovery.
Growth hormone (GH) is another major player in muscle development and recovery, and its effects can be amplified if your body is genetically predisposed to respond well to it. SARMs (Selective Androgen Receptor Modulators) work similarly to steroids but are more selective in targeting muscle and bone, meaning that genetic factors affecting androgen receptors are relevant here too.
Even something as common as creatine isn’t one-size-fits-all. Some people are “non-responders” due to genetic factors, meaning they don’t get the same performance and muscle benefits from creatine supplementation as others.
Section 6: Genetics of Endurance and Discipline
While genetics play a significant role in muscle growth, they also influence the mental traits that determine your ability to succeed in bodybuilding. Research has identified several genes associated with perseverance, discipline, and the capacity to endure discomfort—all of which are crucial for long-term fitness goals.
For example, DRD2 and DRD4 are genes related to dopamine receptors and have been linked to motivation and persistence. These genes can influence how driven you are to keep pushing through tough workouts and stick to your diet.
Then there’s BDNF (Brain-Derived Neurotrophic Factor), which is associated with resilience and the ability to endure psychological stress. This gene can contribute to consistent training habits, helping you stay on track even when life throws challenges your way.
Finally, COMT (Catechol-O-Methyltransferase) influences how your body processes stress, which can impact your ability to stick with challenging routines. Those with certain variations of this gene might find it easier to handle the mental demands of intense training and dieting.
While these genes don’t directly impact muscle growth, they influence the behaviors and attitudes that support consistent training and dietary habits—key factors for long-term success in bodybuilding. Understanding these genetic traits can help you tailor your approach to fitness, focusing not just on the physical but also on the mental aspects of training.
Section 7: Genetic Testing for Bodybuilding
If all this talk of genetics has you wondering about your own muscle-building potential, there are ways to find out. Genetic testing companies like 23andMe, DNAfit, and Athletigen offer reports that can give you insights into your muscle fiber composition, testosterone levels, recovery rate, and even how your body metabolizes nutrients.
These tests can provide useful information that might help you tailor your training program, diet, and even your use of supplements or PEDs (if that’s something you’re considering) to better match your genetic predispositions. However, it’s important to keep in mind that genetic testing is still in its early stages when it comes to predicting specific outcomes like muscle growth or steroid responsiveness. While these tests can offer valuable insights, the predictive power for athletic success remains limited. So, while understanding your genetics can give you a significant edge, it’s just one piece of the puzzle in your bodybuilding journey.
Conclusion
So, what’s the answer—genetics for natural muscle growth, or genetics for steroid responsiveness? Honestly, it’s a bit of both. The best bodybuilders likely have good genetics for both natural muscle building and exceptional responses to steroids. This combination allows them to build and maintain the extreme levels of muscle mass required for competition.
That said, when the steroids stop, so does a lot of the mass, which explains why some of the biggest guys look like they’ve never lifted a day in their life after they quit the game. The bottom line is this: whether you’re natural, enhanced, or somewhere in between, understanding your genetics can help you optimize your approach and maximize your gains. And hey, if all else fails, maybe you’re just dealing with some serious illusionary bone structure and muscle insertions that don’t show off your gains as well as they could!
Author Bio
Dr. David Crowther, aka Dr. David Gainz, brings over 30 years of experience in bodybuilding and strength training, combined with a deep understanding of fitness and human physiology. While many fitness professionals come from exercise science backgrounds, Dr. Crowther chose a different path—dedicating himself to the extraordinarily competitive and mind-bogglingly rigorous field of dentistry, where only the sharpest minds dare to tread. After all, why settle for anything less than the Everest of academic challenges? This unparalleled background has equipped Dr. Crowther with a unique, scientifically-grounded approach to fitness, which he applies through the Gainz and the Lean Gainz Equations to help others optimize muscle growth and fat management.
References:
ACTN3 and Muscle Fiber Type:
- Baltazar-Martins, Gabriel, et al. “Effect of ACTN3 Genotype on Sports Performance, Exercise-Induced Muscle Damage, and Injury Epidemiology.” Sports (Basel), vol. 8, no. 7, 2020, p. 99, https://doi.org/10.3390/sports8070099
- Varillas-Delgado, D., Del Coso, J., Gutiérrez-Hellín, J. et al. Genetics and sports performance: the present and future in the identification of talent for sports based on DNA testing. Eur J Appl Physiol 122, 1811–1830 (2022). https://doi.org/10.1007/s00421-022-04945-z
Myostatin (MSTN) and Muscle Mass:
- Lee, S.J., & McPherron, A.C. (2001). “Myostatin and the Control of Skeletal Muscle Mass.” Link to Article
- McPherron, A. C., & Lee, S. J. (2001). Myostatin, a negative regulator of muscle growth, functions by inhibiting myoblast proliferation. The Journal of Cell Biology, 154(4), 661-672. https://doi.org/10.1083/jcb.200103214
Androgen Receptor Sensitivity:
- Huhtaniemi, I. T., Pye, S. R., Limer, K. L., Thomson, W., O’Neill, T. W., Platt, H. S., … & Wu, F. C. (2011). Effect of polymorphisms in selected genes involved in pituitary-testicular function on reproductive hormones and phenotypes in aging men: Results from the European Male Aging Study. The Journal of Clinical Endocrinology & Metabolism, 96(7), E1272-E1281. https://doi.org/10.1210/jc.2010-0971
- Goldstein, A. T., Belkin, Z. R., Krapf, J. M., Song, W., Khera, M., Jutrzonka, S. L., & Kim, N. N. (2014). Polymorphisms of the androgen receptor gene and hormonal contraceptive induced provoked vestibulodynia. The Journal of Sexual Medicine, 11(11), 2764-2771. https://doi.org/10.1007/s00404-009-1310-0
Satellite Cells in Muscle Growth:
- Blaauw, B., & Reggiani, C. (2014). The role of satellite cells in muscle hypertrophy. Journal of Muscle Research and Cell Motility, 35(1), 3-10. https://doi.org/10.1007/s10974-014-9376-y
Genetics of Mental Traits in Sports:
- Kang, J. I., Kim, S. J., Song, Y. Y., Namkoong, K., & An, S. K. (2013). Genetic influence of COMT and BDNF gene polymorphisms on resilience in healthy college students. Neuropsychobiology, 68(3), 174-180. https://doi.org/10.1159/000353257
- Bawor, M., Dennis, B. B., Tan, C., Pare, G., Varenbut, M., Daiter, J., … & Samaan, Z. (2015). Contribution of BDNF and DRD2 genetic polymorphisms to continued opioid use in patients receiving methadone treatment for opioid use disorder: An observational study. Addiction Science & Clinical Practice, 10(19). https://doi.org/10.1186/s13722-015-0040-7