This is a more challenging version of basic crunches.

1. Sit on the balance board with your heels on the floor. Tuck your chin toward your chest, keeping your shoulders relaxed. Lean back.

   

2. Exhale and bring your body upward and sideways so that your arms go over your left leg. Inhale and return to the start position. Repeat 10-15 times, then switch to the other direction. You could also alternate sides throughout the exercise, doing one repetition to the left, then one to the right, and so on. Ensure that you maintain proper breathing throughout the exercise.