Prone
Whether just waking up or finding oneself knocked down, a prone person is one who is lying horizontally on the ground. Being prone is risky, especially in combat situations. As long as this state persists, prone characters have MOV 1 and suffer penalties of –4 to attack and –2 to defense. Standing up takes 1 action. An enemy in close combat range may choose to attack a prone character with an attack of opportunity. To evade this attack of opportunity, the hero must make a check on Body Control (Combat Maneuvers).
Publication: Core Rules page 36