Once upon a time, Jim and Bob both started tennis coaching. Both were intermediate tennis players in their late 30’s and had decided to shift the beer belly and get fit again. Every week, Jim and Bob would play several games of tennis and go for a few runs.
One day, they both started to get pain in their knee when running and playing tennis. The pain lasted several days. Because of that, Jim decided the best thing to do was to rest from all exercise for a couple of weeks, then go back to training at the same intensity. At first it felt ok, but after several sessions, his knee was giving him grief again.