Aerobic capacity is a multi faceted attribute
It's a set of attributes
But what it adds up to is a bigger gas tank.
You can go longer, further, faster and you can recover easier.
It underpins your work capacity, no matter what your work is.
Activities are not aerobic, you utilise your aerobic system to ensure there's fuel available for that activity.
That said, I want you to use as much of your training as possible to develop the effeciency and effectiveness of the aerobic system
You are going to breathe through your nose while training.
If you are doing:
Any "cardio" exercise, running, cycling, circuits, whatever. Keep your mouth shut.
Any "metcon" or "HIIT" style conditioning set, keep your mouth shut
I'll grant exceptions for tests.
I'll grant exceptions for maximum efforts in the anaerobic zones, anything that asks you to max out inside of a minute, you're going to want to open the mouth, but get back to the nose asap.
But if you're going for an 8, 12, 20 minute conditioning session.
Be it 30 on 30 off x 15, or 45 on 15 off x 25 or whatever, keep the mouth shut.
To assist you in maintaining discipline, to eliminate the natural urge to give into the instinct of mouth breathing, hold a small amount of water in your mouth.
A small sip is plenty
This will assist you in getting the most out of your aerobic system, building an engine that never quits