Cherie Gruenfeld, 81, is an Ironman Hall of Famer who completed her first marathon at age 42. She retired from competing at 78 with 14 world titles, and still competes in half-Ironmans and ...

Zone 2 dominates the heart rate training conversation. It’s the backbone of the 80/20 rule. It’s where you thrive on easy runs. It’s the effort level you’re told to lock into for long runs and ...

Running has long been hailed as the king of cardio. It's free, accessible and an efficient way to get your heart pumping. Still can't stand it? You're not alone. The things that make running such a ...