Technology is provided for restraint systems for use with head mounted displays and head mounted displays incorporating the same. The head mounted display includes a display unit including a display housing and one or more display devices. A retention assembly attaches to the display unit to support the unit on a user's head. The retention assembly includes at least one tensioner mechanism including a housing having an anchor portion coupled to the display housing and a slider positioned in the housing. A strap is coupled to the slider and configured to support the head mounted display on the user's head. A tension element having a first end portion coupled to the housing and a second end portion coupled to the slider provides a constant force on the strap to comfortably pull the strap against the user's head in order to retain the head mounted display on the user's head.