A method for improving athletic or physical performance in a human includes administering to the human a composition or supplement formulation including a single administration of inorganic nitrate (NO3−；), a single administration of inorganic nitrite (NO2−；), or a combination thereof； and an additive. A method for increasing endurance in a human includes administering to the human a composition or supplement formulation including a single administration of inorganic nitrate (NO3−；), a single administration of inorganic nitrite (NO2−；), or a combination thereof； and an additive.
