This is ultimately what killed my mum. She stopped moving. Once that happens so many things in the body just don't work so well. Combined with her other ailment

This is ultimately what killed my mum. She stopped moving. Once that happens so many things in the body just don't work so well. Combined with her other ailments her body just didn't work properly any more. She initially went down-hill after she was weaned off the steroids she had been on during treatment for a benign brain tumour. Obviously the tumour and the radiotherapy didn't help things, but her health dropped off a cliff when the steroids stopped, she lost all her strength. I often wonder if she'd still be around now if they had just kept her on them and worked on her mobility. Keep moving. You don't have to run marathons or go to the gym for it to have a positive effect.