I'm taking a 2 week hiatus from running (and praying my calf will finally heal) and a friend is letting me borrow a bike. I don't think I've ever had a bike other than a beach cruiser, I now this is a "regular" bike. So how far/ hard/ fast/ long do you have to bike ride for it to count as exercise? Or cardio? I don't have a gym membership, so no spinning classes.
Otherwise, I'm walking. I'm open to other suggestions for cardio as well. Thanks