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Did you know DNA affects your response to endurance training?

PPARGC1A, the gene that foils the best-laid plan to boost your endurance

If you were to pick two random people off the street, equally matched for variables like age, sex, body type and fitness level, what’s the likelihood that, with proper training, both of them would finish a marathon? Purely based on genetics, 9 out of 10 times, both people will complete the race, which means there’s a 10% chance that one of them won’t. Everything else being equal, these odds are influenced by a single gene, PPARGC1A. This gene can affect our aerobic capacity, as well as how trainable our bodies are to take on a strenuous endurance activity like running a marathon.

Aerobic capacity is a measure of how well the body makes use of oxygen. For instance, a healthy, untrained man consumes between 35-40 ml of oxygen in a minute. Whereas an elite male runner, of the same weight with a higher aerobic capacity, can use as much as 85 ml of oxygen in a minute. As you can imagine, there are more than a few differences between an endurance athlete and someone who is not as active – the heart of an athlete is better at pumping oxygen to the body and, even more importantly, the muscles are better at using this oxygen to power them.

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When we sprint, we use ‘fast-twitch’ muscles that give us a powerful burst of energy. Fast-twitch muscles produce energy without oxygen, resulting in the the production of lactate in this anaerobic environment. In a marathon we would use ‘slow-twitch’ muscles. These muscles are rich in mitochondria, the cell’s powerhouses, and use oxygen to generate energy. The slow-twitch muscles of an endurance athlete are so rich in mitochondria that they not only use oxygen more efficiently, but they can also break down the lactate produced by exhausted fast-twitch muscles and use this lactate as an alternative source of energy. 

An exception to the benefits of endurance training can be seen if you inherit a version of the PPARGC1A gene called rs8192678. The PPARGC1A gene gives instructions to make PGC-1α, a protein which impacts our aerobic capacity and endurance in several different ways. PGC-1α turns on genes involved in energy production, facilitates the switch from fast-twitch to slow-twitch muscles, and regulates the number of mitochondria found in our muscles. Exercise can increase the amount of PGC-1α, and studies also show that artificially elevating its levels can enhance performance, exercise capacity, and oxygen uptake.

However, people who inherit the rs8192678 version don’t appear to reap the same levels of benefits from regular training. According to one study, after nine weeks of regular training, the increase in aerobic fitness was lower in people with the altered version of PPARGC1A compared to those with the normal version of the gene. In another study, people with rs8192678 lacked an exercise-induced increase in slow-twitch muscle fibres, so it is not surprising that rs8192678 is underrepresented amongst elite endurance athletes.

Many of us have a reason for exercising, such as just wanting to lose a bit of extra weight or to complete in our first marathon. We assume that regular exercise will boost our stamina and enhance our cardiovascular fitness to protect us from disease. However, it is becoming increasingly clear that genetic differences have a lot to do with the type of exercise that will benefit a given person. PPARGC1A is one such example where individuals with the altered version don’t benefit as much from endurance exercise. Maybe the time has come to take the guess work out of your workout and let your genes dictate the best exercise regime that can help you live long and prosper.

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