Both Mazzeo and Knowles are employees at Seward & Kissel. While finishing his undergrad degree at New York University, Knowles, 23, interned at the Manhattan-based firm in 2012. He’s now a legal assistant there. Mazzeo, 28, is an associate in the business transactions group, covering M&A and private equity cases. She started at the firm in 2010, just after graduating from Fordham Law School.

The duo’s interest in running goes deeper than J.P. Morgan’s annual 5K race in Central Park. Mazzeo and Knowles are both long-time runners. Mazzeo’s been racing since she was eight and Knowles started at fourteen. They competed on their alma maters’ cross-country teams: Mazzeo during her freshman year at Villanova and Knowles throughout his time at NYU.

Though the 2014 Corporate Challenge was Knowles’ first win, Mazzeo already boasts a gold medal. She finished on top in 2012. (Mazzeo organized Seward & Kissel’s team that year. Knowles wasn’t eligible to compete because of his intern status.)

But the 2012 race reignited a crippling pain. “I was so injured that I almost collapsed near the end of the race,” says Mazzeo. She first tore her hamstring in high school, and has re-torn it multiple times since. A torn hip flexor also “led to all sorts of additional injuries.” Mazzeo endured multiple surgeries in 2013, only to be told that she would never race again. Ever motivated, she still entered that year’s Challenge—but had to drop out. “It was one of my saddest days ever. I felt like I let down the firm,” remembers Mazzeo. “I was depressed for a year about it.” Knowles, free of his intern status, ran and placed fourth.

Mazzeo decided to battle back by setting a goal for gold in 2014. She continued to run before work and complete core workouts after she clocked out—all while working full-time at Seward & Kissel. Mazzeo also helped Knowles train smarter. She introduced him to a group of competitive runners at the New York Athletic Club, where he practices every day after work.

At the 2014 race, Mazzeo and Knowles were ready to win. Just before the starting gun fired, Mazzeo thought, I will either win this race or die. “I had mentally resolved that if I put myself on the starting line, I was going to win the race no matter what, unless my leg ripped out or I dropped dead during the race,” she says. “I would not have physically allowed there to be any other result, regardless of who showed up that day.”

Knowles fears were a bit less dramatic. “You really don’t know what’s going to happen at the end of a race,” Knowles explains. “It can really be anyone’s day.”

It was their day. Knowles and Mazzeo finished the 3.3-mile course in 16:25 and 19:08, respectively.“Winning together was awesome. Nothing could have made that day better,” says Mazzeo. After the race, Dave and Denise celebrated with the rest of the Seward & Kissel team at an after party—and the firm is honoring the winners with a lunch party later this week.

“When you are working toward goals, whether in running or your career or both, you inevitably need to make sacrifices,” says Mazzeo. “But the other piece of that is not sacrificing so much that you lose sight of what makes you happy.” Running and winning, it seems, are the perfect combination for these two Seward & Kissel colleagues.

The second night of the Challenge, held on Thursday, saw Charles Murphy of Arch Insurance Group and Alexandra Cadicamo of Goldman Sachs finish with times of 16:40 and 18:50, respectively. The overall team winners for both nights have not yet been announced.

In an earlier version of  this story the name of the law firm Seward & Kissel was spelled incorrectly as Serward & Kissel. Also a sentence in the earlier version stated that “Mazzeo combated that depression by setting a goal for gold in 2014.” which inaccurately described her situation. The story now reads “”Mazzeo decided to battle back by setting a goal for gold in 2014.” Fortune regrets the errors.