What happens if you just keep slow, without speeding up? Have you tried swimming, restorative yoga, yin yoga, yoga nidra - I go to a yoga studio and I realize that if you cannot afford a gym, you also cannot afford a yoga studio, but there must be free options via YouTube. All of the above styles of yoga are relaxing and not exerting, and all very good for you. I think you might be a person who benefits from slow exercise.