This is a key workout for any triathlete/time-trial specialist because it asks you to ride at an effort that is just beyond what you would normally race at and then it demands consistency while in the effort. Jeremy's goal was to produce two intervals lasting ten minutes a piece where he would keep his Power output right at his Power Threshold of 342 watts. This is a little different experience mentally, as well as physically, when compared to the more typical intervals where Jeremy would have an entire Power range that he can ride within. You don't have the luxury that you normally have during a normal interval, where if you aren't feeling well on a particular day you can decide to ride at the lower end of your Power range. Ultimately because of the intense concentration necessary in trying to keep your Power output steady during a Power Threshold interval, this ride will sharpen your mental focus at the same time that it helps to create consistency in your riding ability.
Another element to becoming strong at time-trials is your ability to becoming more efficient and reducing your level of perceived exertion while in the "red zone". What you begin to create with Power Threshold intervals is a more efficient engine that operates more like a car on the highway using cruise control rather than a car driving in the stop and go traffic of the city. I think that you would agree that if you were in the midst of a long interval you would appreciate having cruise control, right? Your body has a much better chance of adapting to the stress of the interval when you are successful at keeping your Power output steady and limiting the fluctuations in your Power. For the triathlete one major result of being more efficient is a more controlled heart rate and less overall stress is placed on the body. Now that is something to get excited about because after an efficient bike split you will have more to give on the run than ever before, and since that is where the race is usually won or lost, that's a huge competitive advantage.
So far what I have seen in Jeremy is that when he has to crank up the intensity he does so very easily and it's not like his heart rate doesn't jump right up there with his effort, but once he is into a prolonged Threshold type of effort he can continue to pound out the watts and his heart rate barely budges. It is after seeing Jeremy's efficiency on this ride that I can appreciate why he has been so successful with his endurance endeavors.