I really don't agree with the idea that 110% effort is necessary. Being that the amount of tension needed to grow more penis, which is nearly 100% soft tissue, is not 1000lbs of force then why would you treat it as a maximum effort tug-o-war? The whole point of this method, or theory, is that you only need a SMALL amount of tension to change the size and shape of the tissues in the penis.
As for the idea of "training to failure" in regards to bodybuilding, I'm glad that it's working for you. Regardless of what your progress has been so far I can guarantee you that at some point you will burn out. Your CNS can not and will not sustain that level of activity because as it goes your body will adapt to the system and will ultimately require more training volume, different movements, varied sets and rep schemes, etc etc. HIIT training has been discusses ad infinitum among the Strength and Conditioning coaches the world over, and there is very little value placed upon the theories or principles of HIIT.
Another note on this is that "failure" can either be mechanical, nervous system related, stress from life, not eating enough calories, training too frequently etc etc. Genuine muscle failure is CNS governed, and this is a nearly impossible threshold to reach because the muscles can no longer recruit the larger motor units to move the weights and the smaller units, slow twitch fibers, are not strong enough to move the load. This is the primary reason that a weight starts to feel "heavy" during a set because MUs are falling off due to fatigue. This is a good thing, but you're missing out on a whole lot of muscle growth and strength gains by training to this point because the Large fast twitch fibers have the greatest potential for growth. This means that if you take a heavy load and move it for 1-3 reps with good speed for multiple sets, usually between 6-10 sets, that you will see fantastic size gains as well as strength gains without ever coming close to failure.
If anyone is interested try this with a Bench Press with 80-95% of your maximum weight on the bar and do sets of 2-3, while moving the bar with as much speed as possible (note: this does not mean dropping the bar to your chest, the negative is always controlled but the reverse of the movement is to move the bar with great technique as quickly as possible), and perform this for 8-10 sets. I can assure you that you will feel worked, and more than likely spent using such a heavy load for a high number of sets.