Ectomorphs are the longer, leaner body type. It’s usually defined by having narrower shoulders, lankier limbs, thinner bones, and less body fat. It often goes along with having a higher metabolism. Most ectomorphs describe themselves as being naturally skinny and often have a hard time gaining weight.
Maybe that describes you perfectly, maybe you aren’t sure. These tests will help you figure out if you’re an ectomorph or not. They’ll also determine how much of a ectomorph you are, how that will affect your ability to build muscle, and what your genetic potential is.
To do that, we’ll teach you how to measure your collarbone length, your wrist thickness, and your muscle-to-tendon ratio. This is how researchers determine whether you have an ectomorph body type, but the tests are simple enough that you can do them from the comfort of your home.
Ectomorph Test #1. Do You Have Narrow Shoulders?
In our article on aesthetics and attractivenesses, we talk about the most attractive shoulder-to-waist ratio. In a nutshell, the broader your shoulders are compared to your waist, the more attractive your body looks to women. Genetics can help with that, certainly, but attractiveness is based almost entirely on how lean and muscular you are (study).
After all, having broad shoulders is just a proxy for strength, and having a lean waist is just a proxy for leanness. If you have a muscular upper body and a lean waist, then your bone structure won’t matter very much. Women don’t care about our body type, they care about whether we’re in shape or not.
However, the more we understand our body type, the easier it’s going to be to get into great shape. Figuring out if we have narrow shoulders relative to our hips is a great place to start because it’s almost entirely genetic, and it can have a big influence on our muscularity.
I initially read about this a decade ago in the old Scrawny to Brawny book by Dr John Berardi. In it, Dr Berardi suggested that if your collarbone-to-hip ratio is 1.46 or higher, then you have an ideal frame for building muscle. Digging into the research, there are indeed a few studies proving that we can use that ratio as a way of predicting our overall size and muscle mass.
Two of these studies are especially interesting.
The first is a study out of Johns Hopkins University titled Body Mass Prediction From Skeletal Frame Size in Elite Athletes. In this study, the researchers took elite athletes who competed in various sports, measured their collarbone-to-hip ratio, weighed them, and established a way to predict body mass based on bone structure.
The strength athletes, such as the Olympic weightlifters, were the broadest and most muscular, with a ratio of 1.5. These are the mesomorphs, and they really are naturally bigger and stronger. The endurance athletes, such as the decathletes, were the narrowest and thinnest, with a ratio of 1.3. These are the ectomorphs, and again, they really are naturally thinner.
A follow-up study titled Body Mass Prediction From Stature and Bi-iliac Breadth in Two High Latitude Populations confirmed the findings from Johns Hopkins, but more importantly, proved that the findings were applicable to the general population, not just elite athletes. They found that the Inupiats (aboriginals of Alaska) have a 1.38 collarbone-to-hip ratio and are slenderer than Finns, who have a 1.41 ratio (study).
In both studies, the researchers found that these body type differences were predictive, meaning that by taking these shoulder and hip measurements, we can get an idea of how big and muscular we can naturally get. All body types can build muscle, but guys with a more mesomorphic bone structure are going to have a slightly higher muscle-building potential than guys with a more ectomorphic bone structure.
If you want to figure out whether you have a mesomorphic or ectomorphic frame, you can measure the length of your collarbones (bi-acromial breadth) and then divide it by the width of your hip bones (bi-iliac breadth):
To figure out how long your collarbones are, use measuring tape to measure the distance between the outermost parts of your shoulder bones. This doesn’t include your upper arm bone or your shoulder muscles, but just where your shoulder joint begins. Also keep in mind that we’re measuring the distance between the joints, so hold the measuring tape out a little bit in front of your body so that it doesn’t curve around your chest.
Then do the same thing with your hips, measuring between the outermost part of your upper hip bones, again without bending the measuring tape.
Once you have these measurements, divide your collarbone length by your hip width to get your ratio.
Bone Breadth Ratio = collarbone length / hip width
- If you have a ratio under 1.4, you have a more ectomorphic body type
- If you have a ratio of 1.4–1.45, you are average
- If you have a ratio of 1.46–1.5, you have a more mesomorphic body type
For an example of someone with amazing natural muscle-building potential, we can look at the classic bodybuilder Steve Reeves. Even as a young teenager, you can see that his collarbones are quite broad and his hips are quite narrow:
However, even ectomorphs can build impressive amounts of muscle mass, especially if their goal is just to look strong, healthy, and attractive.
A couple good examples of that are Ryan Gosling and Brad Pitt. Both have ectomorph body types, but Ryan Gosling has a narrower ectomorph build, whereas Brad Pitt has a slightly broader ectomorph build. If you’re an ectomorph, chances are that you’re somewhere in the middle.
What does having narrow shoulders mean for building muscle?
This research shows that ectomorphs naturally carry less muscle mass and that mesomorphs tend to make better strength athletes. However, if your goal is to become strong, muscular, and healthy, it won’t make as much of a difference as you might expect. Most research shows that our genetic muscular limit is only about 10% lower than average. And since hardly anyone gets even close to their muscular potential, that’s hardly any limit at all.
For example, if you look at Ryan Gosling and Brad Pitt above, both of them are ectomorphs, and neither of them are anywhere near their natural muscle-building potential. If you want, you can become far bigger and stronger than either one of them.
If you’re curious about how big and strong you can get, and how quickly you can do it, here’s our article on ectomorph muscle and strength potential.
Ectomorph Test #2. Do You Have Thin Bones?
This is the original hardgainer test. In the 1950’s, the famous bodybuilder Reg Park began noticing that “the small-boned type” didn’t build muscle as easily as other body types. The term hardgainer was coined shortly thereafter.
Reg Park wasn’t a scientist, mind you. He didn’t actually measure anyone’s bone thickness, and he didn’t prove a causal link. It was just an observation. It sparked a line of research, though, and a couple decades later, Dr. Casey Butts proved that there is indeed a relationship between bone thickness and muscle-building potential.
However, there isn’t a link between bone thickness and the rate of muscle growth. In fact, guys who are naturally thinner tend to gain muscle more quickly than guys who are naturally bigger. This is because thinner guys are further away from their genetic limit, allowing them to grow at an accelerated rate. That’s why most skinny guys can gain 30–40 pounds within their first year of lifting weights.
There has also been research showing that some people resist fat gain more than others. For example, in a famous 1999 study, the researchers overfed people by 1000 calories and measured how much weight they gained. Some of the study participants gained as much as 9 pounds, whereas other participants gained less than a single pound. This study (along with many others) proved that some people have a harder time gaining weight than others. We call these people “hardgainers.” (Here’s our article going in-depth on why it’s so hard for hardgainers to gain weight, and what you can do about it.)
Anyway, when we’re talking about someone having a fast metabolism, we use the term hardgainer. When we talk about someone having a thin bone structure, we use the term ectomorph. This test measures the thickness of your bones, so we’ll call it an ectomorph test.
To see how narrow your bones are, you can measure how thick your bones are and then compare that to your height, finding our second ectomorph ratio. The best place to measure your bone thickness is in your wrists and ankles because, unless you’re extremely overweight, those measurements are determined almost entirely by your bone thickness.
Wrist size is most closely related to arm muscularity, whereas ankle size is more closely linked with leg muscularity. For the purposes of this test, we’ll use our wrists.
Bone Thickness Ratio = Wrist Circumference / Height
To find out whether you have an ectomorphic bone thickness, measure your wrist circumference and then divide it by your height (in cm or inches). If the number you get is smaller than 0.1045, you have thin wrist bones, which is a sign that you’re an ectomorph.
To figure out what an exceptionally thick bone structure is, Dr Casey Butts took the wrist and ankle measurements of bodybuilders from the 40s and 50s, before steroids were available. The thinner bodybuilder Ron Lacy (Mr. America 1957) had a moderate ratio of 0.1058, whereas the thicker bodybuilder John Grimek had a ratio of 0.1138. Dr Butts compared their bone size against their muscularity to see if it placed a limit on their muscular potential.
After measuring the proportions of hundreds of bodybuilders, Dr Butts found that men with a ratio of 0.1111 or greater were able to become substantially bigger than average. Their genetic muscular potential was about 10% higher. He called these guys “easygainers,” but we’ll call them mesomorphs.
To be clear, a 10% increase in genetic muscular potential isn’t much for the general population. Most people never reach their genetic muscular potential anyway, and once a guy looks strong, he reaches a point of diminishing returns, where becoming even bigger and stronger won’t make him any healthier or more attractive.
By the time a guy can deadlift 400–500 pounds, squat 300–400 pounds, and bench press 200–300 pounds, becoming even stronger isn’t going to have a big impact on his health or appearance. This means that this upper limit of muscularity is really only relevant for strength athletes and bodybuilders. In that case, though, best to be a mesomorph.
Anyway, moving back to our body type tests, we’ll use a ratio of under 0.1045 to denote an ectomorphic build, and a ratio of over 0.1111 to denote a mesomorphic build.
- If your ratio is over 0.1111, you have a mesomorphic bone thickness
- If your ratio is 0.1045–0.1111, you have average muscle-building genetics
- If your ratio is under 0.1045, you have an ectomorphic bone thickness
However, we quickly realized that not a single member in our community had a ratio that was over 0.1. We aren’t just ectomorphs, we’re extreme ectomorphs. For example, my wrist circumference is 6.5” and my height is 74” (6’2), making my ratio 0.088. (In metric that’s 16.5cm divided by 188cm, still giving a ratio of 0.088.) With wrists this small, I’d still be classified as an ectomorph even if I reduced my height to 5’4″.
I contacted Dr Casey Butts about this, and he told me that having an exceptionally thin bone structure, like I do, is rare enough in the bodybuilding world that his calculations don’t account for it. He predicted that I’d be able to exceed his predictions of muscularity, and he was right: I have.
This goes to show that if you’re on the extreme side of being an ectomorph, the calculators that predict muscularity aren’t calibrated for you, and so they might underestimate your potential.
How does having thin bones affect our ability to build muscle?
As we mentioned above, having a more ectomorphic bone structure is linked to a roughly 10% decrease in our genetic muscular potential. This doesn’t mean that we build muscle more slowly. If anything, we build muscle more quickly. However, having thinner bones does mean that we’ll hit our genetic limit at a lower body weight.
Given how few people reach their genetic limit, this shouldn’t be a big issue, but it might mean that you need to train for muscle mass more deliberately than guys who naturally have more of it. For example, a guy with thicker bones will likely carry more muscle mass by default, and so he might be able to maintain a pleasantly muscular physique just by staying fit and healthy. An ectomorph, on the other hand, might need to deliberately lift weights and gain strength in order to become strong and healthy.
Sometimes having thinner bones is a disadvantage, such as when trying to fill out the sleeves of a t-shirt, maintain a healthy posture, avoid concussions, or avoid broken bones. As such, again, we tend to benefit from lifting weights, which is going to fill out our frames with muscle mass, make our bones denser, strengthen our posture, and protect our spines.
Sometimes having thinner bones is an advantage. We have the potential to be quite strong and athletic for our size, being fairly light even after gaining quite a lot of muscle. That’s a great asset when it comes to running, doing bodyweight exercises (such as chin-ups), or playing sports with weight classes. It’s also easier on our joints, given that they need to bear less weight.
Another benefit is that men with thinner bones tend to be considered more attractive by women. The most famous Hollywood actors are all ectomorphs, with narrower bone structures. This is true with guys like Johnny Depp and Leonardo DiCaprio, although you could argue that this has little to do with their physiques, and you’d probably be right. They’re mainly known for having attractive faces and personalities.
What’s more interesting is that when you consider the actors who are known for having the most attractive bodies, again, it’s a list of ectomorphs. Some good examples are Ryan Gosling, Brad Pitt, Cam Gigandet, Paul Walker and Michael Fassbender, all of whom have thinner, ectomorph bone structures:
This goes outside of Hollywood as well. The top male models have thin bone structures, and many of the athletes who are considered attractive have ectomorph builds as well. Take a look at the top male model Mr. Ward and the soccer player David Beckham:
So what should you do if you have thin bones? Thinner-boned ectomorphs do best when they lift weights and bulk up. The more muscle we can add to our frames, the healthier we’re going to be, and the better we’re going to look.
With that done, relax and enjoy the attractiveness benefits.
Ectomorph Test #3: Do You Have Full Muscles?
The third and final ectomorph test has to do with the relationship between our muscle bellies and our muscle tendons.
Most people know that lifting weights can make our muscles thicker, making us bigger and stronger. Most people don’t know that lifting weights can also make our muscles longer, improving our strength and flexibility. No matter how much we lift, though, we cannot change the length of our muscles in relation to our tendons, which can have a big impact on how our physiques look and perform.
An easy way to test your muscle belly size is by measuring how big your biceps are relative to your tendons. If your muscle bellies are smaller, it will be harder to develop big biceps, but the muscles will contrast sharply against the tendons right next to them, giving you more attractive muscle peaks.
To determine your muscle-to-tendon ratio, flex your arm to 90 degrees, face your palm towards your biceps, and see how many fingers you can fit between your biceps muscle belly and your forearm. (See the video for an example.)
- If you can fit 3 or more fingers between your biceps and forearm, you have an ectomorphic muscle-to-tendon ratio.
- If you can fit 2 fingers, you’ve got an average muscle-to-tendon ratio.
- If you can fit 0–1 finger you have a more mesomorphic muscle-to-tendon ratio.
In the above video you can see me easily fitting three fingers between my biceps and forearm, slotting me firmly in the ectomorph category. With bodybuilders and fitness models, this is quite rate. However, when you look at guys a little further away from bodybuilding, you see far more famous ectomorphs. Some top tier actors, like Ryan Gosling and Brad Pitt, are ectomorphs who have very small muscle bellies.
What should you do if you have a low muscle-to-tendon ratio?
The main place that guys notice smaller muscle bellies is in their arms. It’s not that it looks bad, it’s just that their arms tend to start off looking lankier, and often require some extra isolation work in order to fill out a shirt sleeve.
Some guys can get away with growing their arms with compound lifts, but you probably aren’t one of them. If your arms are naturally lankier, build your routine around big compound arm lifts like chin-ups (for the biceps) and overhead presses (for the triceps), but also include plenty of isolation work, such as biceps curls and triceps extensions.
Also, remember that your biceps and triceps are just a small part of your upper arms. You can add tons of girth to your arms by training your other upper-arm muscles, such as your brachialis, brachioradialis, your deltoids, and all of your forearm muscles. The best way to do this is to use a larger range of motion when doing your arm exercises:
- When doing chin-ups, for example, start from a dead hang and bring your chest all the way up to touch the bar.
- When doing overhead presses, bring the weight down all the way to touch your chest.
- When doing curls, start with your arms fully extended, and bring the bar all the way up to your chin.
- When doing rows, reach all the way down, and then pull the weight all the way up to your torso.
The larger your range of motion, the better you’ll stimulate the main movers (such as your biceps and triceps) and the more you’ll involve all of the muscles that can assist in the movement, including all of the other muscles that can bulk up your arms.
Overall Ectomorph Muscle-Building Genetics
Okay, so let’s say you have a stereotypical ectomorph body type, as I do. That isn’t bad. Yes, it might ruin your chances of becoming an Olympic weightlifter, but it also increases your odds of becoming a decathlete. However, most of us aren’t trying to become professional athletes. That changes things.
Being strong, healthy, and attractive is different from pursuing professional sports, and we don’t have a disadvantage there. Yes, it can be harder for ectomorphs to become as strong as other body types, but it’s also much easier to stay lean. We benefit from lifting weights and bulking up, they benefit from doing cardio and losing weight. It’s not better or worse, our body types just favour a different kind of exercise.
The ectomorph body type is also quite popular with women, for whatever reason. For an exaggerated example, compare the mesmorphic wrestler Brock Lesnar with the ectomorphic model Sean O’Pry (the highest paid male model):
Lesnar’s strong mesomorph physique is great for strength sports and bodybuilding, whereas O’Pry’s ectomorph physique not only lines up perfectly with health ideals, but most women also consider it extremely attractive.
Also note that O’Pry isn’t anywhere close to his genetic muscular potential. Even if his genetic muscular potential were 10% lower than average (as is typical with ectomorphs), he could still gain at least another 30 pounds on top of that physique before brushing up against his genetic limits. His genetics would never be a limitation for him.
To be clear, neither body is better than the other, but each is better at different things. Given that we have more in common with the ectomorph on the right, I would recommend aiming for a body more like that. His face may not be something we can acquire, but that body is realistically achievable for every ectomorph.
In fact, given how far O’Pry is from his genetic potential, that physique isn’t all that difficult to build. It’s something you could do with a good diet and three hourlong workouts per week. It wouldn’t even take that long. A year, at most.
Women aren’t looking for the next Steve Reeves or Arnold Schwarzenegger, just a guy with a strong, healthy physique who will make a great father and make his family feel safe. Think more along the lines of Bradley Cooper, Jake Gyllenhaal, or Shia LaBeouf.
How Should Ectomorphs Exercise?
Ectomorphs often make the mistake of assuming that lifting weights is for guys who want to look like bodybuilders. Yes, it’s true that bodybuilders build their physiques by lifting weights, but even if you just want to build a little bit of muscle, you should still be lifting weights. After all, lifting weights is the type of exercise designed to help guys become bigger and stronger.
For example, Wolverine doesn’t look like a bodybuilder, but Hugh Jackman (above) was deadlifting 405 pounds to get in shape for that role. In fact, deadlifting 405 pounds is a good benchmark of strength if you want to build a visibly strong physique, as are benching 225 pounds, squatting 315 pounds, doing chin-ups with 50 pounds around your waist, and pressing 135 pounds overhead. Even for an ectomorph, all of those goals are realistic.
You don’t have to use a barbell, of course, but the same principle holds true if you’re using dumbbells. You’ll still want to hit the equivalent strength standards.
The problem is, most ectomorphs realize that their body type isn’t built for strength sports, and so they’re drawn to the types of exercise that line up with their natural strengths. They gravitate towards calisthenics, cardio, martial arts, and general physical preparedness, such as CrossFit and P90X. That can be frustrating, though, because it doesn’t help them build muscle mass, and so it fails to help them build strong, healthy, and attractive physiques.
Remember that the fitness model who represents P90X, Tony Horton, built his physique with bodybuilding before being hired to represent P90X, at which point he became a little smaller. Same thing with the calisthenics guys. Most of them build their muscle with weights before moving on to calisthenics.
If your goal is to be bigger and stronger, it’s best to be deliberate about gaining size and strength. It’s best to do a program that’s specifically designed to help you bulk up. I suspect that once you start following a good bulking program, you’ll realize that your ectomorph genetics aren’t any kind of limitation:
If you want a program that will teach you absolutely everything you need to know about building muscle as an ectomorph, you’ll love our Bony to Beastly Bulking Program.