Fast-twitch, Slow-twitch

Sunday Letter | #324

After the meet — 2000

My senior year of high school I was on the cross-country team, and to this day I still remember my first 5K. The race was on a cold, clear morning, at a high school not far from ours. My new red-and-blue race shoes were light as air – probably half the weight of my usual runners – and the thin polyester uniform felt like barely wearing anything at all. I was ready to run.

These races have a mass start: everyone lines up together and you all go at once. Though, now that I think about it, we might’ve split into two groups and staggered the starts. I got in a long row with my teammates and the runners from other schools, and waited for the signal. Was it a flag? A long beep? Some kind of starting gun? I forget what the signal was, but I won’t ever forget how I reacted to it: by completely ignoring our coaches’ warnings for new runners to pace ourselves. As soon as the signal went off, I sprinted to the front.

Reader, I led that race. For a whole glorious fifteen seconds. In that first fifteen seconds, I had boundless energy. I thought, I could run the whole freaking race like this! I remember seeing my coaches chuckling and shaking their heads as I zoomed by.

It only took fifteen more seconds for my body to remember physics. Another thirty and my joints and muscles were starting to stiffen. Even the air around me seemed to grow slowly thicker. First I fell behind the elite runners who were both supernaturally gifted and well-practiced – the ones who could sprint the entire race, more or less. Then I was passed by the runners who were just below the elite tier (but still very fast) and who’d been running for years. Eventually I was passed, too, by those runners who might not have had the natural speed and talent, but did have the training and work ethic. Who knew their target pace and stuck to it.

You can probably tell I’m setting up a metaphor here, but it’s maybe not the one you think. I was first reminded of that cross-country meet a few years ago when I got the results of a DNA test – one of those ones where you send in a tube of spit to have your genome sequenced. The report I got back confirmed, for the most part, a bunch of things I already knew – that I’m 99.9 percent Chinese; that cilantro tastes to me like soap; that I don’t get the “Asian flush” when I drink alcohol. But the report also said a few things I didn’t know, that I didn’t realize the test could detect. And one of those things was muscle composition.

Very briefly: we have two types of muscle fibers, fast-twitch and slow-twitch. Fast-twitch muscles have more of that explosive power (think sprinters, running backs, jumpers). Slow-twitch fibers don’t contract as quickly, but also tire less easily, and are typically more predominant in elite endurance athletes. Michael Jordan probably has more fast-twitch muscles; Lance Armstrong probably more slow-twitch. My report showed a CC genotype on the rs1815739 marker of the ACTN3 gene. Or, in 23andme’s flattering plain english:

Jack, your genetic muscle composition is common in elite power athletes.

For years I’d been telling myself that, because of my inclination toward cross-country over track, toward writing novels over short stories, that I was, both physically and creatively, a long-distance runner. But could it be that this whole time, I was really a sprinter?!

Now, I realize that these are only probabilities here, and genetics are not destiny, etc. etc. But something clicked for me when I started thinking of myself as a sprinter. Or potentially a sprinter. The next time I ran on the track at the local YMCA, instead of trying to jog for ten minutes or for a mile and a half, I opted for short, hi-intensity intervals instead. I ran the way I might’ve run just for fun as a kid: to see how fast I could go. It was nothing short of liberating.

Lately, as I’ve been reflecting on how to release any shame and guilt around my writing practice, I’ve been thinking again about those fast- and slow-twitch muscles. I’ve been thinking about how all have our own creative type, and part of maturing as an artist/human is knowing your self and type –– or types – more deeply, knowing what methods and practices and environments and schedules and motivations best suit you. You might be faced with the same task as another person. You might have to run the same long race. But might you approach that race differently, if you knew your mental and creative composition was more fast-twitch than slow-twitch?

For me, the lens of fast- and slow-twitch helps me see that my work on manuscripts doesn’t always happen at the steady clip I’d like to think it does. There are spurts of progress on my novels, weeks where I write every day and do deep, significant work and do it quickly. Then there are stretches where I plod away and barely make a dent, despite sitting down consistently every day.

I think back, also, to how that first cross-country meet ended.

I was coming over the final, gentle hill, and could see a bigger group of spectators lining the path to the finish. By then, I’d been passed by at least two-thirds of the field, but I sized up the remaining distance and knew that I still had some juice left. I pushed myself a little harder. Then I heard a woman cheering for her son, who wasn’t far behind me. “Come on, you can beat him!” she yelled over my shoulder. I could hear him getting closer. Uh-uh. Not going to happen. For that last stretch, I broke into a flat-out sprint. I crossed the finish line without getting passed.

And while I didn’t set any team records that day, I did finish my first race. I finished it with a time that I wouldn’t beat for the rest of the year, even when I remembered to pace myself.