Prior to their use on the tennis courts, nets were employed strictly for trapping newspaper-stealing neighbors or dredging Loch Ness to discover America's Next Top Monster. Ensnare opponents in a vigorous volley instead with today's Groupon: for $10, you get one group cardio-tennis class at Giammalva Racquet Club in Spring's Wimbledon Subdivision. Helmed by Texas Tennis Hall-of-Famer Sammy Giammalva Jr., Giammalva Racquet Club uses a variety of fun and technical classes to fashion future pros. The one-hour cardio-tennis class fuses music and aerobics with training to burn each racketeer's calories while fostering scorching serves, soundtracked swings, and melodic grunting. Intimate class sizes of up to 15 allow expert coaches to lavish individualized attention and impart instruction to students of all levels and ages.