The prone position means a human is lying face down on the stomach. This position is popular in yoga as the starting point for various maneuvers. It is also used in health care settings, physical therapy of the back and strength-building exercises.
The prone position for babies is a controversial topic as it is often considered a factor in sudden infant death syndrome. While it is more natural for babies to sleep on their tummies, some health care experts advise parents to put their children to sleep on their backs. The prone position is used during "tummy time," to help acclimate a child to this position and to strengthen head and neck muscles.