From Project: Redcap
Body Levels were the way of tracking damage (wounds) to a character in Ars Magica from First Edition through Fourth Edition. A character had several body levels: OK, Hurt, Light Wounds, Medium Wounds, Heavy Wounds, and Incapacitated. When a character was injured, he would check off one or more Body Levels on the character sheet. The highest unchecked Body Level indicated the character's current wound status.
Loss of Body Levels was progressive: if a character was at Light Wounds and then got hurt again, even by the smallest amount possible, his condition would deteriorate to Medium Wounds. Some injuries caused the loss of more than one Body Level at a time.
Body Levels in Fifth Edition.
Body Levels on the ArM5 Character Sheet
The history of this page before August 6, 2010 is archived at Legacy:body_level