Genetic Limits and Differences in Training (and how to surpass them)

By on November 20, 2020

If you give two athletes the exact same training program and they both put in 100% effort, their results will not be identical.

This is a simple truth that most people recognize. But it raises some interesting questions: to what extent is our physical destiny set? Is there any point in training for skills and traits that don’t come naturally?

What are the mechanisms of these genetic limitations and advantages? How do we maximize our genetic gifts and minimize the impact of our weaknesses?

Overcoming Genetic Limits


While many things are up for discussion when it comes to your physical makeup, something that is non-negotiable is an individual’s physical dimensions. That is to say: the proportionate length of limbs, overall height, and insertions.

There is no one “correct” way to squat.

Limb proportion is a subject that has been gaining more recognition among coaches; particularly as it pertains to movements like the squat.

Genetic differences in squat technique

The simple truth is that there is no one “correct” way to squat. Ankle and hip mobility play a big role and some of this is genetically predetermined. For example: a lifter with a longer femur (thigh bone) versus tibia (shin bone) will need to lean forward more into the squat. We can gain more ankle mobility but we sure can’t get longer tibias short of some painful years-long surgery.

Just to be clear: I am not recommending surgery.

Hip Socket Depth and More Factors Affecting Squat

Then there’s hip socket depth: if you have a shallow hip socket and thick femoral neck, then you will experience a reduced range of motion.

Other factors play a role too: like the femoral neck angle (which refers to the way the top of the thigh bone angles).

We should never judge the squat technique of others without having trained them directly.

Likewise, the comparative length of your arms compared with your legs is of course going to impact on the way you deadlift.

This is why we should never judge the squat technique of others without having trained them directly. Nor should we dogmatically force ourselves to adhere to impossible standards from coaches that have never met us in person.

Of course, limb length also impacts on the distance that a weight needs to be moved.

Packing Muscle Onto Your Frame

Of course, the length of your limb also limits the amount of muscle you can fit into a smaller space. Likewise, the size of your frame will ultimately limit the amount of muscle you can pack on. But of course it takes longer for a much taller person to look dense with muscle as they require more work to fill that larger space.

Boineer physique muscle


The tendon insertion is the point where the tendon connects the muscle to the limb. This is a crucial aspect of strength and performance.

Consider the biceps brachii. This muscle originates at the scapula (that’s right this muscle can also act on the shoulder joint). It then spans the elbow joint to insert at the forearm tuberosity of radius and fascia). Contracting (shortening) the biceps brachii has the action of closing the joint angle of the elbow.

Bioneer Bicep Curl

Essentially, this means the elbow joint is the axis or the fulcrum and the forearm is the lever arm. The force or resistance is located at the hand end. The closer the insertion is to the hand (resistance), the shorter the lever arm will be. This then means that it will be easier for you to lift the weight with the same amount of force coming from the bicep. Bringing the insertion closer to the joint will increase the lever arm, thereby increasing the amount of resistance on the bicep.

Muscle Bellies

Conversely, the distance between the origin and insertion is going to directly affect the length of the muscle belly, which alters the capacity for growth, as well as the appearance of thickness. Someone with a slightly shorter arm may actually have a longer muscle belly if they have longer insertions. This then increases strenght:weight ratio!

Arnie biceps

(Of course, agility is also greatly affected by factors such as strength and height. The planche, for example, becomes significantly more difficult as your legs become longer.)

Aesthetic features like the gap between your pecs and how low down they sit on your chest are also, unfortunately, predetermined. This means that you cannot simply copy someone else’s workout and expect to get the precise same results!

You cannot simply copy someone else’s workout and expect to get the precise same results!

Fortunately, the differences aren’t enough to cause drastic advantages or disadvantages for most regular Joes in terms of performance. You can “make up the difference” with smart training. Keep in mind too, that you may have “optimal” insertions for one muscle but not another! This is one reason we find ourselves gravitating more or less to certain moves and exercises.

If you want to excel in your chosen sport, learning how to play to your own strengths and compensate for your weaknesses is absolutely critical.


Here’s something amazing: there are multiple muscles in the human body that are only present in a percentage of the population. Incredible, right?

For example, the Palmaris Longus is a thin tendon that attaches to the bottom of the wrist but is missing in 16% of people (study). The tendon is very weak however, and so has no significant effect on grip strength. You can find out if you have it by holding your arm out with palm facing upward and touching your thumb to your middle and forefinger. If it’s there it will protrude from your wrist.

Muscle Differences

The pyramidalis is a triangular-shaped muscle in the abdomen that is missing in 20% of the population. Most humans have two!

There are many more examples and this just goes to show the huge amount of variation in the human race.

See also: Introducing the ATSP Hierarhcy: Training for Anything & Everything

In my ATSP hierarchy, I refer to these as “fixed attributes.” These are the unmovable aspects of your physiology that you need to work around.  

SuperFunctional Training ATSP Hierarchy

Metabolism and Plasticity

Is metabolism genetic? This is a big subject to delve into but the simple answer is “to an extent.”

And this is critical. Let’s imagine you take two identical athletes in terms of height and insertion. You give them both the same training program and they work equally hard at it, with the same diet and rest protocols. Do they turn out identical?

Genetic differences in metabolism

Still no. Why? Because they will vary in terms of plasticity. This is one of the most critical features that will determine your success in training.

Your body is designed to adapt to its environment (which includes habits and goals). When we train, we add new variables to our environment to stimulate adaptation. But how rapidly the body changes shape in response to that stimulus is what will determine the ultimate outcome.

Neural Plasticity

The same is true for cognitive performance where greater neural plasticity (brain plasticity) will mean your brain changes more quickly in response to training. A more plastic brain will see growth in the trained brain regions and greater connectivity between them. Thus they will find learning easier – both in the classroom and when learning movement patterns. A more plastic brain may even see greater recovery from stroke and other catastrophic events.

Meditation Plasticity

But note that more plasticity does not always equal better. After all, if our brain changed shape in response to everything then it could pick up bad habits as quickly as good ones. Thus we see limitations on brain plasticity and adaptation (study).

This is complex: there are multiple different “forms” of brain plasticity that can be measured in distinct ways. These range from differences in the number and strength of synapses to variations in dendritic spine formation. Again, you could enjoy optimal performance in some areas and not others.

See also: The Dark Side of Learning: Negative Brain Plasticity

Increasing Neuroplasticity

The good news is that there are mitigating factors and methods you can use to increase your plasticity levels. Seeing as this is something most people don’t train, it’s easy to get an advantage here, even if you weren’t dealt the best hand in terms of genetics. The best way to enhance plasticity? Keep learning! The more you subject yourself to novel stimuli that requires adaptation, the more you will produce the chemicals to support that change.

See also: Neuroplasticity – An in-depth guide to how it works and how to transform your brain

Getting more sleep also helps plasticity, as does consuming a healthy diet consisting of many plasticity-supporting nutrients.

Muscle Plasticity

The rest of the body is plastic in just the same way. Muscles adapt to the environment through hypertrophy, motor unit recruitment, mitochondrial density, and fiber type composition. Changes likewise occur in the tendon, fascia, and bones surrounding the muscles. Given the same amount of training, two muscles may grow at different rates simply due to variations in specific hormones and chemicals.

See also: How to Train for Stronger Bones – Wolverine Training Part One

These hormones are at least partly what we describe as our metabolism. That same metabolism is responsible for how quickly you lose or gain fat (the distribution of fat is also genetically determined which is why it’s almost unanimously agreed that you can’t perform “spot reduction” to remove fat from a certain region – it falls off in a genetically predetermined order).

Metabolism and genetics

Countless genetic variations will impact on your metabolism which will directly impact on your energy levels, your weight loss, and even your mood. This is partly what separates the world into “hard gainers” and “the lucky ones.” But keep in mind that the whole endomorph, ectomorph, mesomorph thing is about as helpful a framework as BMI – which is to say not very. As you’ve probably grasped at this point… it’s a lot more complicated than that!

Weight Loss and Gain

This is also why calorie counting won’t work for everyone. Not because there is an exception to the first law of thermodynamics (conservation of energy) but rather because we can’t accurately know how rapidly the body is burning through those calories. No simple calculation will give you an accurate resting metabolic rate as it can’t account for those hormonal differences.

See also: How to get ripped abs and a powerful core

As I often say, you may not have hyper or hypothyroidism, but you might have a tendency more toward one or the other. It doesn’t pay to think entirely in binary.

Genetic differences in testosterone, growth hormone, thyroid hormones, and even the receptors that allow us to respond to those things will make some people more responsive to training than others.

Genetic Mutations

Perhaps the most striking example of a genetic difference affecting metabolism is the extremely smallpercentage of the population born with mutations causing myostatin deficiencies. Myostatin is a protein produced by the human body that causes the breakdown of skeletal muscle tissue. Variations affecting both copies of the MSTN gene result in some people (and animals) becoming myostatin deficient. This is one of the closest things to a natural super-power and can result in huge increases in muscle mass (up to a 100% increase) with no serious side effects (although this might increase the likelihood of tendon injuries).

Myostatin mutations

But again, this itself can be trained and can be hacked. You can keep your metabolism higher by spiking it more frequently with intermittent exercise throughout the day. You can even control your physiology to an extent by changing your state of mind.

Different foods, varying amounts of sleep, and even the ambient temperature will likewise impact on your resting metabolic rate.

Different foods, varying amounts of sleep, and even the ambient temperature will impact on your resting metabolic rate. Likewise, so too do many medicines and drugs. Steroids effectively work by increasing muscle plasticity. Again, this usage would not be reflected in an AMR calculation for the purposes of calorie counting.

Fiber Type Composition

One of the most hotly debated areas of functional training in particular, is “fiber type composition.” As most of you will know, we have three different types of muscle fiber (although the distinction isn’t quite as clear cut as all that, in reality) which are Type 1, Type 2a, and Type 2x. Type 1 muscle fiber is slow-twitch and is less powerful but highly endurance. Meanwhile, Type 2a is faster and stronger but quicker to fatigue. Finally, Type 2x is “faster” still but also comparatively very rare.

Is fibre type genetic

Marathon runners have large amounts of slow twitch muscle fiber which allows them to run long distances without tiring out. High jumpers have lots of faster twitch fibers which gives them the explosiveness necessary to leap great heights. Bodybuilders need fast twitch in order to build bigger muscles, as this type of fiber is larger.

Some people claim that fiber type can’t be changed on the whole. However, most research suggests that genetics only account for around 50% of variability in the makeup of fiber types on average (reference, this one puts it a bit higher). So, while you might have a bit of a preclusion toward either endurance or explosive activities, it’s also true that you can train to become better at the other.

Even the changeability of your fiber-type composition appears to be partly genetic (reference)!

It has been known for a long time that it is possible to convert Type 2a fibers into Type 2x and vice versa. This is very difficult and the change usually occurs in a downward trajectory (meaning muscle gets less explosive). However, there is now ample evidence to suggest that Type 1 fiber can be converted into Type 2a (reference).

What’s interesting, is that even that changeability of fiber-type composition appears to be partly genetic (reference)! So, your muscle may be more glued to a particular format, or more changeable.

It’s Not Just About Fiber Type

It’s also worth noting that “explosiveness” and power are not just functions of fiber type. We can become more explosive via neural changes that enhance our rate of force production by allowing for greater rapid recruitment of larger motor units comprised of fast twitch fiber. Likewise, we can increase max strength by building more muscle, thus making those existing fast-twitch fibers stronger.

Fast twitch fibre

The efficiency of movement can also translate to faster and more explosive execution.

It’s also possible to make slow-twitch fiber behave more like fast-twitch and vice versa. So, while you might be slow to respond to training, you should keep at it. Place a specific demand on your body long enough and you will change to some extent.

And once again, fiber composition varies from one muscle to another. You might have a more explosive upper body relative to your lower body, for example!

The Bottom Line

The bottom line is this: while I’m all about telling people that they can be anything they want to be with the right training, the truth is that some people are just born for a specific sport. Stand next to a professional rower and you’ll likely find they’re very tall with long limbs, great muscle endurance, with great lat insertions. At my stocky 5’8’’ frame, I’d be unlikely to ever compete with those guys with all the training in the world.

Likewise, if we look at an endurance runner like Mo Farrah, we see someone extremely light with a huge number of slow twitch muscle fibers and perfect biomechanics for running. Again, I’m much more explosive and while I can certainly improve my endurance, I probably can’t reach the same level as Mo.

Me: not built for basketball!

But this is a good thing. This is an argument for training cross-modally. As the vast majority of us will never be world champions in any one event, it makes sense to train ourselves to become better at multiple things. To fully express our unique potential.

These systems all work together, and so we will gain unique and amazing advantages by simply taking our strengths and maxing them out. It’s also an argument for adapting training to your own limitations and not comparing your results to anyone else.

We are so entirely unique.

But Also, We Are Extremely Plastic

Amazing genetics

And don’t be disheartened. While you can’t grow taller once your growth plates have closed over, or change your tendon insertions; the real takeaway should be just how truly plastic the human body is. How adaptable. You have countless mechanisms designed to help you adapt to your environment and this allows for incredible individual expression on top of your unique starting point. The things that people have trained themselves to be able to do in some cases are truly remarkable.

See also: The Permanent Benefits of Training – And Overcoming the Interference Principle

Even your genetics can be changed thanks to gene transcription. Training, diet, and lifestyle factors won’t change the contents of your genetic code, but they can change which genes are active and which are “switched off” thereby leading to permanent changes to your anatomy that can even be passed on to your children.

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About Adam Sinicki

Adam Sinicki, AKA The Bioneer, is a writer, personal trainer, author, entrepreneur, and web developer. I've been writing about health, psychology, and fitness for the past 10+ years and have a fascination with the limits of human performance. When I'm not running my online businesses or training, I love sandwiches, computer games, comics, and hanging out with my family.

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