Annette, I just added in HIIT recently and work out at home. I'm trying to do it twice a week (it's really tough on this ol' body!) and alternating between the treadmill and elliptical. Like Tuesdays on the treadmill and Saturdays on the elliptical. That way I don't overkill myself on one particular activity but once per week, giving that damage time to heal. (I tend to be stupid about things and am a magnet to injuries.
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