AvatarSteve McKennaThe Simple Exercise Upgrade for Six-Pack AbsMen's Health - Jill FanslauYou don’t have to crunch more than an accountant during tax season to score a six-pack. Instead, try the elevated bird dog—a new (and much harder) spin on the standard bird dog. “The bird dog forces you to keep your core stiff,” says David Jack, director of Teamworks Fitness in Acton, Massachusetts …