The biggest reason high intensity training doesnt work for most people is they just can seem to get away from the bodybuilding indoctrination of doing so many sets. They just cant break free of the gravitational like pull of doing set after set. Then, after destroying all that tissue, theyre doing it again in a few days!!!!! If you like doing so many sets/repetition, just take up tennis! It pays well too, LOL!- Best Wishes! Stay Healthy!