Hit the Playground: A local park or school can be a fantastic (and free) alternative to the gym. Hit the monkey bars for pullup practice or hang by your knees for some ab-chiseling, upside-down hanging crunches; race to the top of the slide for some mountain-climber worthy cardio; work your quads with a swing session or grab a bench for incline pushups and triceps dips.
TRX: You probably never realized the excellent upper-body workout you got from hanging on the bars at recess. As an adult, working your shoulders, biceps, triceps and delts doesn’t have to be a drag. Try a TRX class, which channels the same upper-body suspension you’d get from monkeying around. Consider this your calorie-burning, grown-up jungle gym.