Research Shines Light On How Much Genetics Really Impact Fitness

How often do you hear the statement, “It’s all genetics”, when it comes to lifting or athletic endeavors? Throughout internet forums, message boards, and in various athletic settings everywhere that statement makes a debut pretty often, but new research is beginning to question that logic more and more.

Every day in genetic and muscle focused research settings, we’re moving steps closer to understanding the body and just how malleable it is. If you’re in the camp of thinking that your genetics are a pre-destined track for athletic abilities, then read on. New research is pushing the envelope of what we know in regards to our genetics’ malleability.

The New Research

The other day, I was talking with Dr. Andy Galpin (one of the authors on the case study) about muscle fibers for an article, and one of the topics we hit on were the findings of the cast study below. Researchers followed two monozygotic twins who had very different athletic exposures for over 30-years. The researchers’ goals were to explore the ideas of adaptability and heritability for multiple biomarkers in the 52 year old monozygotic twins.

30-Year Long Twin Muscle Fiber Study
Twin Muscle Fiber Study

Monozygotic twins share over 99% of the same genes, so researchers wanted to assess how each twin’s lifestyle over the course of their adult life impacted things like their anthropometrics, cardiovascular health, skeletal muscle, strength, power, and molecular markers of muscle health.

In an press release published by San Francisco State University, they write that each twin reportedly played a variety of sports in high school, but ended up taking radically different fitness-oriented lifestyles over the course of their adult lives. One twin became a truck driver with a more sedentary lifestyle, while the other started running and became a triathlete.

So What Did the Research Find?

This is where the research gets really interesting and provides a lot of insight into just how malleable the body can be. Overall, the twin who endurance trained regularly expressed multiple health differences. In terms of muscle fiber composition, the endurance trained twin had 55% more MHC I (slow twitch) and less MHC IIa (fast twitch) muscle fibers, which could serve as a suggestion of how much our muscle fibers can really adapt to the stimuli put upon them. This research is suggesting they’re much more malleable than previously conceived.

In addition and to perhaps no one’s surprise, the endurance trained twin had a higher VO2 max, anaerobic endurance, relative cycling power, aerobic capacity, and had a lower body fat percentage and bodyweight. Conversely though, the untrained twin had better muscle strength, size, and had slightly better muscle quality. The researchers suggested this could be due to the increased body fat and larger percentage of fast twitch fibers the sedentary twin possessed.

James Bagley Assistant Professor of Kinesiology at San Francisco State University, a co-author on the study said in the article above, “It shows your genes aren’t a cop-out. If your parents are overweight, for example, it might be harder for you to get fit, but this study shows that it’s not impossible.”

Practical Takeaways

With this research, the idea of genetics being a completely limiting factor in athletic ability and lifestyle is becoming more nuanced than ever. This research is some of the first of its kind, as the duration (30+ years) is much longer than what’s been previously seen, and the muscle fiber compositions varied much greater than what other studies have shown.

Researchers plan to follow-up with the twins every five years, so it’s going to be really interesting to see results as time passes. From the study above and my recent talk with Dr. Galpin, our muscle fibers are much more malleable than what’s normally perceived.

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Jake holds a Master's in Sports Science and a Bachelor's in Exercise Science. Currently, Jake serves as one of the full time writers and editors at BarBend. He's a Certified Strength and Conditioning Specialist (CSCS) and has spoken at state conferences on the topics of writing in the fitness industry and building a brand. As of right now, Jake has published over 1,100 articles related to strength athletes and sports. Articles about powerlifting concepts, advanced strength & conditioning methods, and topics that sit atop a strong science foundation are Jake's bread-and-butter. On top of his personal writing, Jake edits and plans content for 15 writers and strength coaches who come from every strength sport.Prior to BarBend, Jake worked for two years as a strength and conditioning coach for hockey and lacrosse players, and was a writer at the Vitamin Shoppe's corporate office. Jake regularly competes in powerlifting in the 181 lb weight class, and considers himself a weightlifting shoe sneaker head. On the side of writing full time, Jake works as a part-time strength coach and works with clients through his personal business Concrete Athletics in Hoboken and New York City.