This looks like fun, not so much. Well at least the idea seems to make a bit of sense. The O2 Trainer by Bas Rutten is designed to build up your lung strength with resistance training. Simply put, the O2 Trainer ($49) makes it harder to inhale air. Exhaling has no resistance and you can adjust the inhale resistance from 1MM to 14MM. If nothing elseâ€¦ doing your resistance training with restricted airflow will make exercise with no air resistance seem much easier. Video after the break.