After a six-year hiatus from running, Anne Mahlum got back into it big time, finishing up her goal of completing a marathon on every continent. Her last remaining one? Antarctica. She crossed that off her list on March 17, and she did it for a good cause: She ended up raising $102,927 for the New York City chapter of Back on My Feet, a nonprofit she had founded in 2007 that uses​ running and community to empower people experiencing homelessness. While Mahlum hadn’t laced up in six years, she wasn’t inactive. She had been busy growing her boutique fitness company...