Ditch your shoes at the beach and follow those footprints to find a great workout. "Running barefoot on sand is great for your feet, and really challenging--plus, you get a great workout in only 10 minutes," Barrett says. The uneven terrain strengthens your ankles, arches and leg muscles, building power throughout your lower body, and burning more calories than a treadmill would. Start out on the hard, wet sand before you tackle the dry, soft kind. Then wade into the water for a soothing foot soak--and a cool down!