a mouth guard seated at least partially on an upper jaw of a user to reduce resistance of air flow in a nasal channel of the user comprises a flange positionable between the upper jaw and an associated upper lip such that the flange extends above a gum line of the upper jaw . a chamber within the flange includes a valve for adjusting the volume of the chamber so that pressure applied by the flange to the upper lip is adjustable to affect dilation of the nasal channel resulting from such pressure , thereby allowing the user to selectably reduce resistance of air flow in the nasal channel .