“On a scale of 1 to 10, your average training difficulty should be an 8, but if you never go to 10 you’ll lose your perception of what an 8 really is. Because of that, a lot of people are really doing a 5 or 6 when they think they’re at 8. An occasional lesson in pain in the gym will allow you to keep things in perspective.
Doing level “10” workouts can be useful, but you must understand how they affect the body and plan your training accordingly. Realize that you will not be in an optimal shape for a few days after doing a stress session, so either plan rest days or program in some easier training in the days after your challenge”