Asynchronous Cardio/pulmonary Exercise

The worst part about aerobic exercise close to your personal limits is that you're gasping for breath and your muscles are burning at the same time. My solution to this is an airtight mask which slightly constricts the volume of air which you are able to inhale, making your lungs work harder and grow stronger. By wearing this mask for several hours per day (or even all night) one can effortlessly build a level of pulmonary health significantly higher than their cardiac health, making exercise much easier. An alternative would be to filter air through a set of baffles filled with water and an oxygen-fixing bacteria, thus reducing the O2 content of the inhaled air and, over time, building a higher red blood-cell count. This variant is more desirable than the air-restriction device because it doesn't alter the volume of air you inhale, just the oxygen saturation, which means your body actually becomes more efficient in its oxygen use rather than just making you better at breathing hard.