Emily McCarthy never expected her destiny to be hauling heavy weights on her back. As a D1 track and cross country athlete in college, she focused intensively on cardio after a childhood spent dabbling in sports like soccer and tennis. "My base has always been as an endurance athlete. I didn't do a lot of strength training," she told Business Insider. That changed while training to become a CIA operative. During a grueling land-navigation exercise, trekking for miles with a loaded pack, map,