By Jen Murphy Sept. 22, 2018 9:00 a.m. ET Dane Chapin, a real-estate executive, goofs off at the Bridges Golf Club in Rancho Santa Fe, a San Diego-area course. Adding a stability ball to his gym routine has improved his golf game. Photo: Sandy Huffaker for The Wall Street Journal One look up close at tennis great Jimmy Connors practicing in the early 1980s gave Dane Chapin a life-changing realization: He would never reach his dream of playing the sport professionally. Mr. Chapin, then a junior on UCLA’s tennis team, watched Mr. Connors, a UCLA alum, at practice one day.