Is it recommended that you use some kind of barrier to protect yourself when giving cpr

Yes you should wear a protective mask to protect from any disease they have and you should only administer CPR if you are certified. otherwise you could get sued if not done correctly

Well if you pick a machine to work on and that's gonna be your exercise if you don't stick to that machine your muscle strength your muscle mass rather will change because you haven't been doing it you change something in your exercise routine which changes your body's form of dealing with things for example you might become weaker or stronger depending on what kind of exercises you do in whether or not the machine you picked actually your muscles grow.

Wat r u trying to