We're talking your basic push-up but—not to worry—with knees on the floor.
Stand facing a staircase with your left foot on the first step, leaning slightly forward from the hips (don't bend at the waist). Pulling up and forward with your left leg, bring your right foot up to the step; tap the toes of your right foot on the stair, pause for a second, then step back down. Keep your left foot on the step until you complete all reps; then switch sides.
Week 9: Do your established routine—two sets of ten reps of squats, sit-ups, back extensions, and toe stands. Add two sets of five push-ups.
Week 10: Do the above plus two sets of five step-ups on each leg (20 reps altogether).
Week 11: Do two sets of ten reps each of squats, sit-ups, back extensions, toe stands, and push-ups, and two sets of five reps of step-ups.
Week 12: Do two sets of ten reps of all six moves.
So far, the strength routine includes six moves every other day. "Now it's time for some weights," says Miriam Nelson, PhD, director of the Center for Physical Activity and Nutrition at Tufts University. Add two moves with three- to five-pound dumbbells (use more weight if this is easy) for your arms.
Stand with your feet hip-width apart, hands down at your sides holding the dumbbells, palms facing in toward your legs. Keeping your elbows gently pressed against your sides, bring your forearms forward and up until the weights are at shoulder height with palms facing in toward your body. Lower back down.
Sitting in a chair while holding the dumbbells, bend your arms so the weights are in front of you at shoulder height, parallel to the floor (the inner ends should be just in front of your shoulders), palms facing forward, away from your body. Now slowly press the dumbbells up until your arms are straight. Don't lock your elbows, and don't aim for exactly above your head; the weights should end up slightly forward. Pause, then lower.
Week 13: Do your established routine—two sets of ten reps of squats, sit-ups, back extensions, toe stands, push-ups, and step-ups. Add two sets of five biceps curls.
Week 14: To the above, add two sets of five overhead presses.
Week 15: Do two sets of ten reps of the first seven moves, plus two sets of five overhead presses.
Week 16: Do two sets of ten reps of all eight moves.