The field test consists two 8 minute all out efforts. The wttage average from these will be used to determine the training zones until the next field test. We usually do a few of these per year. I use my Cycle-Ops Indoor 400 since the results are completely comparable. Riding outside, especially in the winter, presents too many variable from wind, to windchill, to traffic, road conditions, etc. Plus, inside is mentally tougher which never hurts. The last time we did these, which I think was in mid-January, I held 365 and 370 watts. This was in the middle of a tough winter of training and the third of the four indoor time trials. The indoor tt effort is around 14:30-15:10 and using my Powertap while on their Compu-Trainer my power at its best was around 368 and 390 respectively. The Compu-trainer was always about 20-25 watts higher. Not sure which is truly accurate but the important things was they were consistent on each ride. it certainly helps with the power having other riders competing on the course at the same time. I warmed up for 20 minutes today pushing 170-200 watts. I started the first effort at 280 watts and by the 30 second mark had my target power at 370 knowing that was where we were the last time. My goal was to ride close to 375. In the end I rode the first 8 minutes at 369 and the second at 371 so essentially the same as last January. Watts per kg would be right around 4.8. I'd have to hold about 385 to reach that illusive 5 wts/kg. Tought to do for this length fo time but not impossible.