17 September 2019

Genetics 101

by Aaron Hoey 0

  It is almost inevitable when discussing human differences, especially when it comes to body composition and sports performance that the topic of genetics will arise. Unfortunately though, genetic variation is a poorly understood concept. As with anything, a more thorough understanding assists with dispelling misconceptions, thus allowing a better standard of knowledge to proliferate….


It is almost inevitable when discussing human differences, especially when it comes to body composition and sports performance that the topic of genetics will arise. Unfortunately though, genetic variation is a poorly understood concept. As with anything, a more thorough understanding assists with dispelling misconceptions, thus allowing a better standard of knowledge to proliferate. This can help each individual to focus his or her energy and attention where it is required in order to achieve the desired outcome. This article will focus primarily on the genetic difference in organisms that can lead to such drastic variance in any outcome. A future article will focus more so on how environmental factors can impact on said outcomes.


What do we mean by the word “genetics”?


Genetics refers to the genetic properties or inherited characteristics of an organism. As humans, we acquire our genetic makeup from our parents, and as such, have an increased chance of acquiring certain pieces of genetic material. The genetic material we end up acquiring will lay the foundations for certain traits and characteristics – therefore we have a higher than average probability of developing similar characteristics to our parents (based on genetic factors alone and without even considering environmental factors).

A simple example would be if two individuals of dark skin complexion procreated, their offspring would have a very strong probability of acquiring a dark skin complexion.  Charles Darwin’s theory of “survival of the fittest”, suggests that certain “beneficial traits” are more likely to be passed along to enhance the offspring’s chances of surviving in the world.


More specific to our purposes here, the word “genetics” as it stands in the current fitness sphere seems to be loaded with certain assumptions and misconceptions. Examples of these are how individuals may claim to be averse to losing body fat due to having “bad genetics” which leads to a slower metabolism, or perhaps the misconception that champion bodybuilders with large amounts of muscle tissue did not have to work hard for their results as they are genetically “blessed”.


Standard distributions.


Certain traits are dichotomous, and can be simply divided into a yes/no paradigm. Examples of such would be sex, which is either defined by one having either an XX or XY pair of chromosomes. Other traits can be ordered according to a magnitude of scale, such as an individual’s height. In such a situation, individuals fall on a spectrum where there will be an average height, and 68% of the population falling within 2 standard deviations of the average. At either end of the spectrum we have a small percentage of the population that falls into either the “short” or the “tall” categories. The height of the curve may differ, depending on how far away from the norm the extremes deviate.

This is important because a more conceptual knowledge of individual differences will allow for a more systematically authenticated model of how individuals differ and the magnitude in which they differ, especially when it comes to more nuanced models of assessing if someone is genetically blessed or at a detriment.

For example, if we now plot the height of all humans out separately with sample sizes based on gender, we will have 2 standard distribution curves that will look approximately as follows.

We can conclude from this data that, on average, men are taller than women. Of course, there is a large portion of the female population taller than the male population, and denying this would be a misunderstanding of the data. If one was to further categorize, one may find that certain populations of females (basketballers) are on average taller than another sub group of male athletes (horse jockeys). We have to ensure that we are comparing apples to apples when making generalist statements – outliers and exceptions to the rule will always exist.


The purpose of this example was not to highlight the genetic differences between genders, but rather to put forward a relatively easy to understand example before we progress to the more nuanced topics of aesthetics and strength.


Genetics in sports

One thing which is not often touched on in the discussion of genetics is how many outlying traits can be viewed as either an advantage or a disadvantage depending on which lens you are viewing it with. For example, being 7-foot-tall would be considered advantageous for many sports (football ruckman, basketball, high jump), while subsequently being disadvantageous for other sports (horse jockey, powerlifting, bodybuilding). Therefore, one cannot be deemed “gifted” until it has been specified in which domain they are gifted in.


Another example of this would be an individual’s percentage of fast twitch and slow twitch muscle fibres. While the average individual would possess an even spread of both, if one were to take muscle biopsies from champion marathon runners, the results would indicate that they have a genetic predisposition to have more type I or slow twitch muscle fibres, meaning that they are genetically more efficient at sub maximal intensity exercise due to their ability to utilise substrates for energy and expel waste, therefore resulting in high amounts of fatigue resistance. A muscle biopsy from a sprinter on the other hand would likely return with a higher percentage of fast twitch muscle fibres, indicating that the fibres are quick to turn glucose into usable ATP and hence can create high velocity contractions. While both athletes may be meticulous in their training, dieting and recovery strategies, their ability to ascend to the top in their individual sports is strongly aided by their inherited genetic traits.


Even within a single sport, there can be genetic trade-offs observed. Let us take powerlifting for example, a sport that takes the collective sum of the best attempts at the squat, bench and deadlift to determine who is the stronger individual. These three lifts are quite different, and a different orthopaedic profile would serve as advantageous for each lift. This means that one cannot be perfectly suited to both the bench press and deadlift however, as optimal arm length for the bench press vs the deadlift is opposing, with the ideal bencher ideally having shorter arms to decrease range of motion, while the ideal deadlifter would have long arms to also decrease range of motion. Similar issues apply with femur-to-torso length ratios when comparing the squat and deadlift.


When it comes to genetics as it pertains to muscle hypertrophy and fat loss, we can also look at genetics through multiple lenses. Let us first take muscle hypertrophy as an example. If we look at individual muscle hypertrophy response to resistance training and plot the results along a standard distribution, we will have high responders, average responders, and non-responders. While this data doesn’t necessarily explain why individuals respond so differently, the fact that we see such a startling difference in outcome from the same intervention suggests that there is an underlying mechanism which is responsible for the difference.




When it comes to muscle hypertrophy, it is difficult to be truly be certain if one falls into the category of what could be considered “gifted” without some kind of genetic testing. While other phenotypes such as height and limb length are quite easily observable, one’s genetic potential to acquire lean mass is difficult to observe and quantify as it has a large amount of influential factors. For example, while one individual’s muscle protein synthesis levels might be very responsive to resistance training, they may also have weak connective tissue by comparison and spend a greater amount of their career injured. In addition to this, someone’s insulin sensitivity or blood pressure might decay rapidly when they gain weight, whereas for another individual these general health metrics might be more robust during a caloric surplus – these are also factors that impact how much muscle someone can and will grow. Furthermore, one’s physique when untrained does not give a good indication of their genetic potential, therefore looking at pictures from before a weight lifting intervention is an invalid method of assessing if one is gifted unless there is some kind of normative data to compare to.


When we look at competitive bodybuilding however, many who end up placing highly in bodybuilding competitions are more than likely predisposed to having certain characteristics that individual’s ability to achieve lower levels of body fat, and their physical shape, which is dictated by bone structure as well as muscle insertion points – among many other things.


How does genetics influence training and nutrition interventions?

While genetic variance certainly exists, we have to hold the magnitude of variation in context. As humans we are 99.9% the same. We have the same general body structure with a head, a spine and four limbs, as well as organs located in the same locations and made out of the same tissues. The fact that we are so similar is why we can prescribe training, nutrition and medicine interventions while being quite confident of the outcome.


Regardless of one’s genetic make-up, principles still remain such as having to be in a calorie deficit to lose fat, and exposing the muscles to sufficient magnitudes and durations of tension to facilitate hypertrophy. If we liken the human body and our physical progress to a game of chess, the common denominator is that we are governed by a predetermined set of rules. Our ability to win the game (make physical progress), may be made slightly easier or more difficult depending on the opponent being faced (our genetics, something outside of our control). Nevertheless, by playing our best game possible and always striving to be more knowledgeable and more disciplined in our actions, we increase the likelihood of winning the game regardless of our opponent. A focus on improving our capacity to win will yield far greater benefits compared to obsessing over the capabilities of our opponent (worrying how our genetics influences our potential), or the opponents of other players (genetics of other).


Being tactical is to do what you can with what you have – Saul Alinsky

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