to come through the nose otherwise your core is weaker in action and you will not bring in as much oxygen. This holds true for exhalation through the nose for it affects the core area in strength releasing the carbon dioxide out of the body so you can get a complete transfer from oxygen to carbon dioxide. How you breathe through your nostrils affects so many functions of the body it is art unto itself. Lowering your shoulder stress before you even start your work out will let person become emotionally and physically engage in the work out faster with more fat burning time during the work out and boredom will not be part of the workout. Boredom is the mental disengagement of what you are doing at the gym physically.