It's difficult to change overnight but if you are persistent and take one step at a time you will see results!
Jack LaLanneYou should do it against the clock. Say you are going to do 30 laps in 15 minutes. Then you try to do it each day a little faster. That is putting demands on the body, and that is how you build up. You keep up your energy instead of going downhill.
Jack LaLanne