This is also where I think you need to decide on whether or not it is a sport specific applicication. I think we can all agree that kind of endurance training is only good for..well endurance. HIIT and GPP are great ways to stay in shape but running 3 miles a week is not going to win you any 50k's or ultra marathons. I honestly hate running but try to get in 10 miles a week to prep fro triathlons. And I mostly work on the bike(this early in the season and Im only hitting about 150miles a week). Where I start to get worn down is if I load too much strength training with this high capacity I still lift WAY more than the average triathlete but keep it down the closer I get to the season.
That was kind of a basic blurb about over training, although exersize is a complementary stress it can become a very harmful one if over done or not recovered from properly. Almost more important than workload, recovery and nutrition should be watched just as closely.
just my $0.02