I know many people who have become more sedimentary. Many people have fallen, and the odds are they do not return to a walking life. Others have become so overweight they find movement hard. I can speak from experience as I weighed more than Nero Wolfe, the fictional detective. He weighed in at a 1/7 of a ton. You can do the math to find the actual weight.
There are ways we can exercise safely. Below, I have posted YouTube videos that deal with workouts that you can do standing or sitting. If you have balance issues or cannot stand up, do these exercises from the chair. First, check with your doctor if you can do a physical rehab. Second, watch the videos before you do them. Some of these videos can help you wherever you're at. Others may be more advanced and something you could try as you get better.
Most of the advertising you can skip after a few seconds. The ads may be questionable, and with any health ad, before you take their advice, it's always a good idea to check with your doctor or physical therapist because if it sounds too good to be true. It isn't good.
Some of the workouts are from Silver Sneakers. Again, as they get into the exercises, they tell you you can do them sitting down. A few workouts come from two physical therapists, Bob and Brad. These guys have worked with many people who have fallen and maybe broke a bone. They have all types of senior citizens workouts, but watch them before you do them.
A word about sitting and doing workouts: first, they do work. Secondly, they work on the muscles we often experience weakness when we get older. Try a workout, sitting in a chair, no matter how healthy you are. It may help you understand how the workout out might help your older friend or parent deal with their aging issues.
Exercising with balance support can be very helpful. I am not an expert. I have looked at these things and tried them out. They appear very senior-friendly. That is why I advise you to check in with your doctor. You and your doctor know your health better than anybody else, and your doctor may connect you with a support rehabilitation to start your progress. Still, some are walk-in-home, and you may have to find balance support to do the exercises. I hope you find them helpful to keep walking. Here are the links
Senior exorcises https://www.youtube.com/watch?v=8BcPHWGQO44
Bob and Brad https://www.youtube.com/watch?y=cYHOp4h4hAm4
Bob & Brad https://www.youtube.com/watch?v=n8_JcYAN7eU&t=607s
Silver sneakers https://www.youtube.com/watch?v=n8_JcYAN7eU&t=607s
Senior walk 2 miles advance https://youtu.be/jRWKYOhcWWU
Senior sneakers 30-minute walk or sit https://youtu.be/cgyfL6Te_aA
Silver sneakers 15-minute sit or stand https://youtu.be/nTdzz3-01sE
Balance (interesting) https://youtu.be/uth_9K3EmDI
Bob and Brad balance (good ideas https://youtu.be/atMJ2opvCvo