I've had a new coach since the start of the summer after working with the previous coach for about 6 or 7 years. Its always interesting to have someone else look at your training and race results. With the outdoor time trials over for thsi year and the monthly indoor time trials starting in two weeks my coach has been looking over my power data and questioning whether I am really riding as hard as possible. She asked me if I ever train until failure. I said that the closest I come to that would be in the 3 minute power intervals. I might be able to hold 400+ for the first two but then I drop to 380, 360 and lower. She suggested that we test my power over longer times.
After gradually raising the wattage goals and time in the intervals over the last couple of weeks she assigned me two 20 minute efforts at 360 watts, about 10 watts above what I would hold at the 10.2 mile tt at Cleves or the 10 mile at the Blue Streak. Seemed doable even under a non-competitve environment.
I rode out US 52 starting the first effort just past the entry to Coney Island and finished near the Beckjord Power Plant in New Richmond. Average power--350. Seemed like I was holding 360-380 a lot but obviously not enough. HR was at 95% of max or or 109% of FTP at the end and averaged about 102% of FTP. I took about 8 minutes between and started the next effort. I knew 5 minutes in that I wasn't going to be close on the power but HR was way up there. In the end power was about 335 and HR was higher than the first effort by another % of FTP.
While I didn't push so hard that I had to stop I wasn't too far from the point where power was dropping enough that it wouldn't have been beneficial to continue. The other barometer would have been taking my HR to 98% of max or 110-112% of FTP. I can get there but can't hold that for long. It's like doing the VO2 test on the road.
The point here isn't that you should train to failure every time and in fact you really shouldn't but it is good every once in a while to find that point of failure. The best training zone to develop power over time is right around your FTP. Spend enough time there and you'll gradually increase the power that you can hold in that range.