What are the barriers to exercise and the ways around them?

Personal. Embarrassment that you're not as fit as the gymrats can be overcome by saying, "i'm going to be happy because they're happy, and enjoy the show". They'll respect & help you if and only if they see real effort. Boredom can be overcome by anything from an earphone with music to exploring inner space; the first marathon runner found strength from the "iliad". 1/2 your battle's won already.