Oh yes it is. I had ankle and knee pain running more than 40 km a week, too. I'm simply getting too old for more than 2 hours of intense sport a day, I had to g

Oh yes it is. I had ankle and knee pain running more than 40 km a week, too. I'm simply getting too old for more than 2 hours of intense sport a day, I had to get back to 60 to 90 minutes.