Gluteus Maximus, Quadriceps, Rectus Abdominis
Start laying on your back on a mat or a towel. Bring your hands up by your ears and take your elbows out wide. Then elevate your feet off the floor with a 90 degree bend at your hips and your knees. You want your thighs to be vertical and your shins to be parallel to the floor. Then, keeping your lower back pressed down into the floor, tuck your chin to your chest, draw your belly button down and contract your abdominals to roll your upper spine up off the floor. This is the start position. From here, twist your spine to bring your right shoulder and elbow in towards your left knee. At the same time, extend your right leg out as straight as you can and hover it just off the floor. Keep your lower back in contact with the floor. Return to the start position by bringing your right leg back in next to your left leg as you untwist your spine to return your upper body to the top of the crunch position. Then repeat the process for the other side, by twisting your upper body to bring your left shoulder in towards your right knee as you reach your left leg out straight to hover, before returning to the start position.