Lie on your back with your knees bent and feet flat on the floor. Place your hands behind your head or across your chest. Lift your shoulders off the floor by contracting your abdominal muscles. Lower back down and repeat.
Start in a push-up position, then bend your elbows to 90 degrees and rest your weight on your forearms. Keep your body in a straight line from head to heels, engaging your core. Hold the position for as long as possible, aiming for 30 seconds to 1 minute.
Sit on the floor with your knees bent and feet flat. Lean back slightly and lift your feet off the ground, balancing on your sit bones. Hold your hands together in front of you and twist your torso to one side, then the other.
Lie on your back with your hands under your hips. Lift your legs toward the ceiling, keeping them straight. Lower your legs down without letting them touch the ground and then raise them back up.
Start in a plank position. Bring one knee toward your chest and then switch legs in a running motion. Keep your core engaged and move quickly.