I use it for a 40-minute workout in the pool, light on the cardio, but plenty of work on the muscles. It helps enormously.

Yes; it will help sob from beginning right away and will help you mainain your exercise for a sufficient amount of time to actually feel the difference. Remember, if your 02 sats are good, you can keep going for as long as you can stand it ab=nd not do yourself any harm.

YES