They’re Parents to Two Kids Under Five. They Also Just Crushed Rainier’s Infinity Loop FKT.

The O’Briens had just set the mixed-gender fastest known time (FKT) for the Rainier Infinity Loop. Approaching their target: Mount Rainier, 14,410 feet (Photo: Tracy O’Brien)ADVERTISEMENTTaking on the Rainier Infinity LoopThe Infinity Loop was the second FKT the O’Briens had set on Rainier in as many months. Then, they were off on their great Infinity Loop adventure. “We took about an hour, ate, changed into running clothes, and we were back on the trail,” Tracy said. But for the sake of her girls, she might be retiring from FKTs—at least, anything as intense as the Rainier Infinity Loop.