After several years of plowing my way through New York City’s streets, I decided to join a local running group—the South Brooklyn Running Club (SBRC)—to provide me with company, friendship, inspiration, and conversation. We’ve run the length of Manhattan, traversed Brooklyn, and criss-crossed the bridges that knit the city together. Although I’ve been with them for fewer than three years, it’s hard for me to remember what it was like to run alone.

But a 20-mile training run stubbornly remains 20 miles no matter the company, and when Birgit, a friend in the group, suggested that we try a 5-4-3-2-1 workout that she’d seen posted on the Intertubes, we approached it with some trepidation—not least because the write-up called it “one of the most demanding race-specific workouts a marathoner can do.” What the run entailed was a slow first and/or second mile, followed by five miles at marathon pace; then another slow mile, followed by four at marathon pace; a further slow mile and then three at marathon pace; another slow mile and then two at half-marathon pace; and, finally, a slow mile and another at half-marathon pace. We’d run a total of 21 miles—of which 15 would be at or faster than our marathon pace.

I offered to try out a shorter version of the workout (5-4-3-2) in New York Road Runners’ 18-mile Marathon Tune-Up a week before our scheduled exercise, with only one slow initial mile, and no final slow and half-marathon-pace mile. I’d not been particularly impressed, especially since the year before I’d completed the 18-mile Tune-Up five minutes faster than the 5-4-3-2 afforded. But I agreed to give it another go.

Birgit and I set off from Carroll Gardens in Brooklyn, and timed our two slow miles (9:30 minutes per mile) so that we were facing the downward slope of the Brooklyn Bridge when we kicked on. Our marathon pace would be 8:00 minutes per mile and our half-marathon 7:30 minutes per mile, as we ran up the West Side of Manhattan to the George Washington Bridge and back. We had our hiccups along the way: Birgit’s running belt caused chafing that needed to be addressed, and I failed to put enough vaseline on my nipples, with the inevitable bleeding. I pushed a little too hard on some of the marathon-pace miles, but when I mentioned to Birgit at mile 16 that it wouldn’t be terrible if we didn’t run the final stages at half-marathon pace, she made it very clear that she hadn’t come all that way to slow down or give up.

By the time we ended our run in Battery Park City we were tired, bloody, sore, and elated. Mario Fraioli, the trainer who’d posted the 5-4-3-2-1 regimen, mentioned that the workout would provide “a huge fitness boost and will give you the confidence that you’re ready to tackle your marathon goal,” and he wasn’t kidding. Although we’d completed many long runs between us, the precision, discipline, and cameraderie of doing it together made it nothing less than exhilarating. Something, we knew, had shifted inside us, and when we both completed October marathons with PRs and BQs, we independently thanked the other in our Facebook posts for that long run. It wasn’t just that the 5-4-3-2-1 showed us that we were fit enough and capable enough, or that it gave us the confidence to succeed. It was important that we did it together—a public acknowledgment of the other’s readiness that was a deeper validation than any private accomplishment.

And that’s perhaps why being part of a club matters. When I’d undertaken the shortened version, I’d been doing it alone, albeit surrounded by thousands of others circling Central Park. Even though I was with only one other person a week later, I needed a mirror-companion to check in with and to join me, bloodied but unbowed, in the whoop that the Garmin’s beep at 21 miles let loose. In the long run, that’s what might be what really matters.