Bear with me if my english isn't all there, I am norwegian, and don't have the proper words for everything.
But all the books I read, all the posts I see, I never find anything about static exercise. I learned this when I was a kid, and use it on my bad days.
We all know that building muscle helps burning calories an fat, but when you have trouble walking, it,s not that easy. But this actually has helped me a lot!
It's all about tensing and relaxing your muscles. If you suck your belly in, count to three and relax, count to three and release. Repeat ten times. Then your glutes. Then your thighs. As you go along you will connect with more and more of your muscle groups, - invite them all int this game!! You can do it sitting on a bus or watching TV, in your bed and basically everywhere. It sounds like not that big deal, but you will get sore!! Ans your muscle strength will grow!
I try to do this everytime I remember during the day. I have a rather short attention span, very little patience and a terrible memory, but still I get it done a few times a day, and to me it has been a lifesaver!
You can also work on your flexibility in a similar fashion. Remember to be careful so you don't injure yourself. Just hold up your hand a bit and roll the wrist. Five times left to right, five times right to left. Then the shoulder. You don't have tolifft your arm, just raise the shoulder and roll it left to right five times, right to left five times. And your ankles. You can rotate your waist from side to side ,- look as far as you can to the right, then to the left. But be very careful with your neck!! Never rotate your neck backwords, only from side tide, and never to a point where it hurts.
When you are sitting, lift your leg a little bit and put it down. repeat x times.
You can find hundreds of ways to work your muscles and tendons without ever standing up. It is a light-verion of the plank.
Some gyms have machines with "assisted training" They will move, and you just sit and enjoy the ride. As you get stronger, you can actively follow the motion, or actively resist it for better effect.
It all seems so simple, and not like a real workout, but it does help a lot!!
I have days when I can barely move, and I have days when an hour at the gym is easy as a piece of cake. Some days I can walk for hours, some days I am happy if I can manage ten minutes. But these exercises are acsessible, easy and efficient. Combined with a healthy diet, they can make a huge difference, and increase the number of good days immensly!
Let me know how it works out for you!