Back in the days before Spandex and aerobics, when there were no health clubs or high-tech exercise machines, people who wanted to get fit did calisthenics.

Staples of the military, sports teams and gym classes, these basic conditioning exercises--push-ups and pull-ups and the like--were considered the best way to get strong and fit. In fact, the popularity of the Royal Canadian Air Force's calisthenics program in the late 1950s helped launch the modern fitness movement.

Now--after decades devoted to an explosion of diverse fitness options--these low-tech, low (or no) cost, basic training tools are back. Calisthenics are the mainstay of "boot camp workouts," one of the hottest classes at trendy fitness clubs. New books and videos feature military-style shape-up routines, and there's a boom in outdoor programs led by drill sergeant-inspired instructors who bark their "maggot" charges through basic training regimens.

Back To Basics
The reason? "Anytime you stick to the basics, it's going to work and you'll get results," says Stewart Smith, a former Navy SEAL who trained candidates for the elite group's Basic Underwater Demolition unit.

Calisthenics use your own body weight to provide resistance needed to strengthen muscles, Smith notes, "so you don't need fancy equipment or lots of money to get in top physical condition."

Plus, calisthenics can also provide an aerobic workout. "Try doing a series of exercises called a pyramid where you start by doing one pull-up, two push-ups and three crunches, then do two pull-ups, four push-ups and six crunches and keep progressing until you're doing 10 pull-ups, 20 pushups and 30 crunches, then work your way back down," he says. "You'll get your heart rate up."