Stand with your feet hip-width apart, hands on your hips, your shoulders back and down and your abs pulled in. Take a large step to the front, bending both knees at a 90-degree angle, back knee almost touching the ground. Stand up, swing your back leg forward and “step” into your next lunge. Do 30 lunges and rest. Muscles worked: Core, hips, butt, thighs and calves.