How long does it take to adjust to an increase in altitude (sea level to mountains)?
The air at 5,000 feet has quite a bit less oxygen, so your body and lungs need to generate the capacity to function better that it did at sea level. More Exercise will help, and I assume you aren’t a smoker (if you are, get rid of them!) Wouldn’t be surprised if it takes most of a year before you’re back to normal, but you’ll still benefit from exercise in my opinion.
