If you prefer planking on your forearms, get out of the habit of clasping the hands together in a triangle shape. (mindbodygreen.com)
** If clasping your hands behind your back is not accessible, use a strap or PVC pipe; widen the grip to a place where you can fold forward. (weckmethod.com)
Clasping your hands in front of your groin area draws attention to the wrong place. (inc.com)