The Columbia Center, the tallest office building in the Pacific Northwest, towers over Seattle like some brooding giant. But its 69 flights of stairs are no match for a man with a mission like Dan Nelson’s. He’s got a few things to prove, and on Sunday, March 8, for the seventh year in a row, Nelson, 58, will join 1,499 other firefighters from across the country in marching to the top. The annual Firefighter Stairclimb, in which the rescue workers ascend 1,311 stairs in full gear, breathing into masks and burdened with oxygen tanks every inch of the way, raises funds for the Leukemia and Lymphoma Society.

There’s a lot at stake. Nelson’s father died of leukemia, so every step on that tall snaking staircase is like a barrier to finding a cure, a thing to be stomped on, which he wants to do faster and faster each time. Last year it took him 21 agonizing minutes and 52 grueling seconds to reach the top. Not good enough. The overall winner, Seattle Fire’s 40-year-old Zach Schade, finished in a throat-clutching 11 and a half minutes. Nelson doesn’t think he can best Schade, but he wants to shave minutes off his time and school the men in his age category. Another thing he wants to prove: “There’s too much so-called health-care advice out there telling baby boomers they’re getting old, that they need to fear tendonitis and to stop whatever they’re doing.” The important thing, he says, is to stay active. He would know: When he’s not on duty, he’s Dr. Nelson, a chiropractor and an exercise physiologist, spreading the gospel of fitness.

Nelson, who didn’t become a firefighter until he was 44, trained for the department’s qualifying endurance test by hauling 100-pound sandbags up Laurelhurst’s cruelest hills. Right up until the day he tries to conquer the Columbia Tower, he’ll be scaling stairs at Husky Stadium—with an air mask and 60 pounds of gear instead of sandbags.