NowFitness, St. Louis

The crowd's roar flooded the streets of Chicago as Darcy Zenker crossed the finish line of her first marathon, clocking in at 3:35. After she had been running for years—placing among the top finishers at four half-marathons and competing on the Southern Illinois University track team—she decided she needed a break. She then immersed herself in a new athletic pursuit—group fitness instruction.

Three years later, she became the head trainer of her own boot-camp fitness program, NowFitness, where her years of athletic training and certification in fitness instruction shine through in her workouts. In parks throughout the local area, she and her staff of fellow trainers lead groups through high-intensity workouts that take advantage of their surroundings. She motivates patrons to scale stairs, do crunches on benches, and hoist planks across grassy fields. The trainers also offer a stroller-based boot camp for moms, in which participants blast through cardio and strength-training exercises that incorporate their stroller with baby or a watermelon they've dressed up to look like a baby in tow. In addition to hosting classes, NowFitness pairs patrons with certified lifestyle and weight-management coach Amanda Bickel for a comprehensive five-week nutrition program.