Cardio—even a 15-minute walk—gets your blood pumping and moves oxygen through the body. New York City personal trainer Jen Cassetty also recommends these moves anytime you feel yourself fading. Do two sets of 10-12 reps each.
Stand with feet shoulder-width, knees slightly bent, hands behind head. With your back flat, bend forward until your back is parallel to the ground, keeping weight in your heels and hips. Return to standing.
Stand against a wall with spine touching it from shoulders to hips, then raise arms parallel to floor. Keeping arms and back against the wall, rotate arms upward as far as you can, then down to starting position.
Sit on a chair or bench with hands behind head. Press elbows straight back to stretch your chest and open your lungs, then bend sideways at the waist to crunch to your left. Come back up and repeat crunch to the right. That's one rep.