I'm 70 and just started running again last year. I only sprint short distances though. Like a block at a time or less. But it is at full speed, as fast as I can run. A year earlier I would be lucky to run ten steps. I started our doing what I could. Ten or fifteen steps at a jog.

Six years ago I was 100 pounds overweight and could not run and could not do a lot of things. I give credit for my much better health and physical condition to changing my diet to a very low carbohydrate diet. That diet also reversed my diabetes of over 30 years, got rid of my back and knee pain, and a host of other health improvements. Got me off of a half dozen medications including four injections of insulin a day.

Don't under estimate what eating the wrong food or too much of unhealthy food can do against you in the health and pain department. I was told I would need a knee replacement about six years ago. Now I am doing sprints several days a week without pain. No knee replacement in the plans.

The one thing you DON'T want to do is injure yourself. So proceed cautiously and safely in the department of increased physical activity.