You can do exercise with weights sitting in your chair. Any time you get your arms over your head you can boost your heart rate.
Get some weights and do your arms over your head and out to the side - there should be some wheelchair exercises on line. Do this two or three times a day -you don't have to walk to get benefit.
You can also put the weights on your thigh and raise your legs or heels - if you can stand on one leg - you can do hip exercises by holding on to the back of the chair and raise you get to the side - start slow and switch sides -
CHECK WITH YOUR DOCTOR BEFORE DOING ANY EXERCISE PROGRAM.
We go to Silver Sneakers at our Aquatic center and a lot of us cannot stand for great lengths of time - look for the exercises on line and find something you can do
Good luck -
I am 69 and my husband is 72 - I had lost 40# but now I have gained back 20 and I am so disgusted with myself.