What about trying an exercise bike, namely a recumbent bike? You don't have to support your body weight with your legs because the chair already does that for you, and that can make getting exercise a little easier. You're also leaning back on a recumbent bike and not forced to sit upright like you would on a traditional exercise bike (which can tire out the abs quickly). On top of that, you can use the bike while texting on your phone etc to distract you. Or watch videos on YouTube. That will pass time quickly and before you know it, you'll have gotten in a lot of exercise.