Clara Vinter

5 min read

2025-04-23

by Clara Vinter writer

In my twenties, I loved running. I ran 3-4 times a week for about 15 years, and on top of that, I biked to and from work and picked up the kids from daycare.

-Not because I was training for a race, but because it became my regular routine. Running was something I could always do with ease, -just put on my shoes and head out the door.

There were days when the run felt light and effortless, as if my legs had their own rhythm. And then there were days when every step felt heavy. I often asked myself: is this just in my head, or is there something deeper? Something in my biology that affects how we move?

As a nurse, I’ve always been curious about the connection between the body and our lived experience. Over the past few years, my interest in genetics has grown, not just in terms of illness, but in everyday things, like why some people are naturally quick on their feet while others are steady and enduring.

A Closer Look at ACTN3

One gene that keeps coming up in the research is ACTN3. It influences the production of a protein found in fast-twitch muscle fibers, the type responsible for explosive power, like sprinting. Some people have a version of the gene (the R-variant) that helps their muscles work efficiently in short bursts. Others have a different version (the X-variant), which is associated with better endurance.

Neither version is “better,” but they do seem to set the stage for different kinds of physical strengths.

This may help explain why some of us felt at home on the school track while others preferred long walks or team sports, or why some runners lean toward marathons, while others excel at the 100 meters.

The Power of BDKRB2

Another fascinating gene is BDKRB2, which plays a role in controlling blood pressure and blood flow. This gene impacts how well your muscles can get oxygen during physical activity, influencing endurance.

Research has found that certain variations of this gene are linked to better aerobic capacity, meaning people with these variations may be able to run longer without tiring, or recover from strenuous activity more quickly. If you’ve ever found yourself wondering how some people can push through long workouts with ease, this gene could be one reason why.

MTHFR, -More Than Just Folate

MTHFR, a gene involved in the processing of folate and homocysteine, may not directly affect speed, but it has broader implications for physical health. Variants of this gene can impact how well your body manages inflammation and oxidative stress, both of which are key to muscle function and recovery. For those with certain MTHFR variations, the body may struggle more with these processes, potentially leading to quicker fatigue or longer recovery times after exercise. It’s a reminder that genetics plays a role in both how we perform and how we recover.

Nuance: The link between MTHFR variants and athletic performance is less direct than for ACTN3 or BDKRB2. Poor MTHFR function can affect overall health (e.g., cardiovascular health, fatigue), but its impact on muscle recovery or exercise performance is not as well-established. Lifestyle factors like diet (folate intake) and supplementation can mitigate effects.

The Euphoric Running Gene? DRD4

A year ago, I found something that made me laugh and think, “Is this me?!” There’s a gene called DRD4, associated with dopamine regulation, the neurotransmitter linked to reward and motivation. Some variations of this gene have been connected to increased feelings of excitement, reward, and even euphoria when engaging in physical activity. I couldn’t help but smile when I read about it. It made so much sense! I had always felt a kind of “euphoria” when I was running, -that burst of joy and energy that made the run feel almost effortless, like a natural high. I told my kids about it, and we had a good laugh, thinking that my ‘euphoric running’ was probably linked to this gene. Curious as ever, I looked into it more…-and sure enough, there it was: a genetic link to that feeling I’d always loved during my runs.

Nuance: While DRD4 may play a minor role in exercise reward, FAAH (anandamide regulation) and OPRM1 (endorphin signaling) are the most likely genes to influence euphoria during running, with DRD2, COMT, and SLC6A4 contributing to reward and mood. The runner’s high is a complex, multifactorial phenomenon, and no single gene fully accounts for it.

Beyond Speed: The Influence of COMT

Speed isn’t only about muscles; it’s also about your brain’s response to stress and effort. The COMT gene plays a role in the breakdown of dopamine, the neurotransmitter that affects mood and motivation. If you carry the Val variant of the gene, you might feel more driven, more focused during physical exertion, which could enhance performance in sports or challenging tasks. On the other hand, the Met variant might lead to quicker burnout under stress, which could influence how long you can sustain intense physical activity.

I’ll revisit this gene in a later blog post to dive deeper into its influence.

It’s Never Just One Gene

Of course, ACTN3, BDKRB2, MTHFR, DRD4, and COMT are just pieces of a much larger puzzle. Dozens of other genes influence things like your metabolism, muscle recovery, and how your brain processes physical effort. Your environment, your diet, stress levels, sleep patterns, and overall lifestyle -also shapes how your genetic traits come to life. It’s a complex, beautiful interaction between what’s in your DNA and what you experience in your daily life.

Genomic studies (e.g., Rankinen et al., 2016) estimate that over 200 genetic variants contribute to physical performance, with no single gene being dominant.

Knowing, Not Limiting

I don’t believe we should let our genes define us. But understanding them can help us shift from self-criticism to curiosity. Maybe you’re not slow, maybe you’re built for a different kind of strength. Maybe it’s not laziness or lack of effort, but a body that’s wired to perform in its own way, on its own timeline.

Looking back on those 15 years of running 3-4 times a week, I realize just how much I loved it. I wasn’t racing anyone, but I was racing my own body to see just what it was capable of. And even now, I’m still learning how to listen to what it’s saying. Maybe it’s time to start running again. Just for the joy of it, -and to see if that euphoric feeling comes back?

I´ll let you know. I sure will! 👟👟

…
Clara Vinter
Registered Nurse | Sweden
Writing about genes, the body, and the everyday science of being human

Disclaimer: I am not a doctor, and the information provided here is based on current research and my personal understanding. Gene research is advancing rapidly, and new findings may alter our understanding of genetic influences on health and performance. Always consult a healthcare professional for personalized medical advice or concerns regarding genetics, health conditions, or treatments.