Genetic Trainability: Your Genes Influence Your Workout Results

The big problem with statements like “hard work beats talent,” as us professional fitness trainers and sports coaches often say, is that it always assumes that “hard work” is the answer. However, the undeniable reality is: While hard training (i.e. working out) makes a difference for everyone — It’s the law of averages; put more in, get more out — some people benefit from (the same type of, and same amount of) “hard” training (drastically) more than others.

In other words, some people are more trainable than others based on their genetic make-up when it comes to seeing results from the same given training program. Some people put work in and get little out of it, while others put the same amount of work in and get (much) more out of it.

In this post, I’m going to provide you a variety of the high-quality scientific evidence demonstrating individual variability in (genetic) trainability; how people have drastically different responses (i.e. results) to the same cardio training and strength training stimulus (i.e. workout programs), and discuss how this information should impact the your training.

Exercise Is Medicine! But each Person Needs the Right Type and Dose (based on their Genetics)

Fitness professionals along with others in the allied health community use the  motto “exercise is medicine.” Just as differences in the human genetics can influence how well different people respond to certain medicines (1), our genetic differences can (and do) influence the individual response to the medicine of any particular variety of fitness training. This is exactly why discussing the differences in genetic response to training outcomes (i.e. results) should not be controversial because it is no different than discussing the differences in genetic responses to coffee. (2)

Genetic Response Differences to Cardio Training and Strength Training: The Science

Put simply, science shows that by nature humans vary considerably in both physical and mental abilities, and a good portion of that variation is due to our genes. And, we have very good evidence that familial factors also contribute significantly to variability in our training response (i.e. individual trainability).(3)

Individual differences in training-induced changes in several physical performance and health-related fitness phenotypes are large, with the range between low and high responders reaching several folds. (4)

As you’re about to see, this wide variability in individual (geneticically influenced) training response occurs in both Aerobic Training and Strength Training.

Cardio Trainability: The research showing drastically different results from the same Aerobic Training programs.

Some of the most thorough and high-quality evidence showing the differences in genetic responses to Aerobic training comes from the HERITAGE Family Study. The HERITAGE Family Study consortium is composed of research teams from five universities in Canada and United States: Indiana University, University of Minnesota, Texas A&M University, Washington University, and the Pennington Biomedical Research Center (Claude Bouchard, Ph.D. The head researcher).

Since the HERITAGE (HEalth, RIsk, factors, exercise Training And GEnetics) project began in 1992; as of 2013 there have been 169 publications in refereed journals. See a full list of these publications here.

This study – one of the many HERITAGE studies – subjected 99 two-generation families to stationary bicycle training programs to increase aerobic fitness. All the families received the same training program consisting of three workouts per week of increasing intensity for 20-weeks, and DNA was taken from all 481 participants. The results revealed marked interindividual differences, like: The range in VO2 max improvement spanned from 0% to 100%, depending on the family heritage. About 15% of participants showed little to no improvement, while another 15% increased their VO2max by 50% or more.

According to the study’s principle investigator, Claude Bouchard, “the range of response to training was six to nine times larger between pairs of brothers than within pairs.” (5)


As David Epstein, author of The Sports Gene: Inside the Science of Extraordinary Athletic Performance (the awesome book that inspired this post) puts it, “Statistical analysis showed that about half of each person’s ability to improve their aerobic capacity with training was determined exclusively by their parents.”

Additionally, it should be noted that person-to-person variability in aerobic training responses has been observed not only in the HERITAGE Family Studies, but also in other studies and populations (6,7).

Muscular Trainability: The research showing drastically different results from the same Weight Training programs.

Two studies in 2007 and 2008 at the University of Alabama-Birmingham’s Core Muscle Research Laboratory and the Veterans Affairs Medical Center in Birmingham showed that individual differences in gene and satellite cell activity are critical to differentiating how people respond to weight training.

The 2007 study published in the Journal of Applied Physiology put 66 people of varying ages on a four-month lower-body strength training plan consisting of three exercises: Squats, Leg Press and Leg Extension. Each person was matched for effort level as a percentage their 1RM. (A typical set was performed for 11 reps at 75% of 1RM). As Epstein summarizes, “At the end of the training the subjects fell rather neatly into three groups: those whose thigh muscle fibers grew 50% in size; those whose fibers grew 25%; and those who had no increase in muscle size at all.” 

Epstein goes on to say,A range from 0% to 50% improvement, despite identical training. Just like the HERITAGE Family Study, differences and train ability were immense, only this was strength as opposed to endurance training. 17 weightlifters were extreme responders, who added muscle furiously; 32 were moderate responders, who had decent gains; and 17 were non-responders, whose muscle fibers did not grow. It seems that some people’s body is set better primed to profit from weightlifting as the subjects who made up the extreme muscle growth group had the most satellite cells in the quadriceps, waiting to be activated and build the muscle.”

In addition, other studies like this one run by an international consortium of hospitals and universities have validated these results finding that men and women exhibit wide ranges of response to resistance training, with some subjects showing little to no gain, and others showing profound changes. Five hundred eighty-five subjects (342 women, 243 men) were tested at one of eight study centers. In 12 weeks of study of 585 men and women, upper arm strength gains ranged from zero to over 250%.

Take Away Lessons

One could certainly say that the harder (and more dedicated) one is with their fitness training, the more likely one is to get a positive response. And, I certainly would not argue with that, as More work = More rewards. But, we must not ignore the fact that some people are low (and potentially non) responders to certain exercise programs, whereas others are high responders, as the research evidence above clearly demonstrates. So, if you’re a low responder it’s likely that you’ll still get less results than your peers who are following the same program.

This reality becomes important for personal trainers and sports coaches to keep in mind when they have clients and athletes who don’t seem to be responding (much) to a given training program. In that, sure it’s a possibility that the client or athlete is not working hard enough. But, it’s also a possibility that the client or athlete is working very hard and just not responding well because the program doesn’t fit well with their genetic profile.

The solution for the clients and athletes who aren’t working hard is a kick in their ass. But the solution to the clients and athletes who are working hard (just not responding well to it) is a pat on the back, and an encouraging conversation that informs them about 1) the evidence on genetic responses to different training regimes, so they understand that 2) just because they’re not responding well to this program doesn’t mean they won’t respond to another (different) training program. And, 3) because of this, you (as the trainer or coach) will be happy to help them to look for something that they may have a better (genetic) response by experimenting with different training programs.

Remember: The Foundational training principles (Specificity, Progressive Overload, GAS) are universal. But there are many ways to apply these principles to best fit each individual. This is where the “art” of training comes in. IN that, the “art” is finding different ways (that best fit each individual) to apply the same “scientific” principles.

Lets face it, as important as it is to encourage everyone to “train hard,” it’s also dangerous not to also inform everyone that hard work isn’t everything; it’s your (individual) response to it.

Variations in genetic trainability suggests that innate qualities of each individual ensure that there is no one-size-fits-all sport or method of training. So trainers, coaches, clients, athletes, and parents of young athletes, shouldn’t look at every situation where results aren’t coming (as they are with others) and automatically think its case of “not training hard enough.” This could easily cause those low responders (and non-repsonders), who are working hard, to end up pushing themselves beyond their capacity, which leads them to become overtrained, potentially injured, and very discouraged.

Further Reading

In addition to the references hyperlinked throughout the article, here are some other great resources about Genetics and Strength Training:

The Truth About Bodybuilding Genetics by Bret Contreras

Weight Training: The Importance of Genetics by Matt Brzycki

Muscle Building: Top 3 Factors, Genetics, Exercise Variety & Periodization by Brad Schoenfeld


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