It was narrated that Aishah said: "I never saw the Messenger of Allah ﷺ pray sitting down until he grew old. Then he would pray sitting down and when there were thirty or forty verses left, he would stand up and recite them, then bow".
The Prophet Muhammad was an example for us all in how he conducted himself throughout his life, including his prayers. Even though he was growing older and weaker, he still made sure that his prayers were done properly by standing up for the last few verses before bowing down in submission. This shows us that no matter what age or physical condition we may be in, there is always something that each one of us can do to serve Allah and fulfill His commands.