15 Minute Exercises: Is it ENOUGH?
Walking at a four-mile-an-hour clip is a good pace that helps keep your muscles, ligaments, and aerobic systems in good working condition. It’s easy and anyone can do it. By the way, walking is not only good for the body, it’s good for the mind. It’s a good distraction from the stresses of your day. Jogging and running are also good, even if you do just two miles at a time. Remember though, as noted above, do not exceed five miles.
Also, try going to your local swimming pool – not necessarily swimming laps, but doing what we call aqua jogging or walking. Just 20 minutes of this sort of activity will burn calories, benefit your aerobic system, and benefit your muscles by combining isometric and isotonic activity in a way that’s good for your lower extremities. That’s a particularly good thing for sports officials. Remember that isometric exercise is designed to build and strengthen muscles, while isotonic exercise is designed to tone your muscles. There’s a difference. You can have good muscle tone without strength. Ideally you’d have both.
Cycling from 20 to 45 minutes a day is another good form of exercise. Just be sure you do so in an area where the roads are safe. If you prefer to ride a stationary bike at home or in a gym, that’s fine, too. Don’t try to do too much, though. If you bike strenuously, keep it to no more than three times a week.
https://www.nfhs.org/articles/offseason-exercise-how-much-is-too-little-too-much-or-just-right/