The key is “gradual” working up into a exercise routine.
This is my main exercise video. It keeps my heart in good shape and the wrist weights strengthen upper body by swinging arms.
Notice I do not run, just walk at 25-26 minutes/mile pace, and cover 1 mile distance 5 times a week.
The treadmill is set 1-1/2 to 2 degrees up depending on my mood that day. After the treadmill, I will drink half a glass of water and then pull 15-20 lb (total) weight on the weight machine 23 times. At age 81, I do not need speed, just need to keep some tone in body.
https://www.youtube.com/watch?v=I55ZxIwbuOU
https://www.youtube.com/watch?v=I55ZxIwbuOU