Most runners should train the same way that competitive runners do, even if they jog only for fitness. Here’s a program that you can follow even if you do not plan to compete. First get a physical exam to assure that you are healthy. Then start out by running every other day until your legs feel tired or hurt. Gradually work up to the point where you can run for thirty continuous minutes.
Then start your training program. Plan one fast and one long workout a week. The other workouts should be at a slower pace and can be skipped if you feel tired. Your fast run can be on Wednesday and your long run on Sunday. Wednesdays, start out slowly and gradually increase the pace until you start to feel uncomfortable as you breathe hard and your muscles start to hurt. Slow down until you recover and gradually pick up the pace again. Repeat until your legs start to feel heavy.
Each week try to improve by spending more time running fast and less time running slow. Take the next day, Thursday, off because your legs will be sore. On Friday and Saturday, jog slowly a short distance. On Sunday, try to run for 30 minutes, and each week, extend the time running until you can stay out for 60 to 90 minutes or more of brisk running. Take the next day off. Then jog slowly on Tuesday and try to run fast again on Wednesday. The same principles can be applied to any endurance sport you use for fitness, such as cycling, rowing or swimming.