Back Balance
Lay the center of your back on the central part of the Bosu, aiming to keep both the upper and lower back in contact with the Bosu.
Lift both legs so that they are bent at 90 degrees, with your hands resting on your knees. Slowly straighten one leg out to your front, taking the opposite hand out behind your head. Hold this position for 10 - 30 seconds before repeating again on the other side, and a further time for intermediates / advanced persons.
Variations
From the same starting position, extend both arms and legs out slowly together. Concentrate on contracting the abdominal group muscles for stability, whilst keeping your lower (lumbar) back in contact with the Bosu at all times.