Lie on your back and open your legs into a diamond shape (known as Butterfly pose in yoga), with the soles of your feet pressed together and knees out wide. Extend the arms overhead.
Curl the torso up, and tap the floor in front of your feet. If this is too difficult, just raise the torso off the floor as high as you can, performing a basic crunch.
Slowly lower back to the starting position to finish off one rep.
Do as many reps as you can for 40 seconds. Take a 20-second rest. Complete four rounds, then cool down.