If you have been using the BBB template for three cycles, this may be a good time to Challenge. If you are new to BBB, do not attempt the challenge. 90% TM is the maximum, 85% is best for those with several years of consistent, proper training. This is not something to do to "jump start" your training or after a layoff. If your body is not in-shape and ready for this volume, you will suffer. With all that being said, the challenge is fun as hell.