A strap is disclosed for a human user. The strap includes a support for the chin of the user, a first support for a first mandible of the user, a second support for the second mandible of the user, and means for securing the strap to the head of the user. The first mandible support is affixed to one side of the chin support and the second mandible support is affixed to the opposite side of the chin support. In a preferred form, the first mandible support and the second mandible support are each from about 1.5 inches wide to about 3 inches wide, and in a preferred range, the first mandible support and the second mandible support are each from about 1.75 inches wide to about 2.25 inches wide. In a preferred embodiment of a strap according to the present invention, the first mandible support is at an angle to the second mandible support of from about 90 degrees to about 140 degrees when the strap is opened flat, as it would be before it is place on the user. In a preferred range, when the strap is opened flat, the first mandible support is at an angle to the second mandible support of from about 100 degrees to about 120 degrees. Typically, when the strap is opened flat, the first mandible support is at an angle to the second mandible support of approximately 110 degrees. In a preferred form, the chin support is at an angle to the main plane of the strap of from about 40 degrees to about 80 degrees when the strap is closed. A preferred range for the chin support is at an angle to the main plane of the strap of from about 50 degrees to about 70 degrees. Typically, the chin support is at an angle to the main plane of the strap of approximately 60 degrees.