I appreciate what
@RojoRacing writes about his effort...often known as "fly and die". It's a romantic approach to riding hard. It makes you feel kind of macho. It also gives you a built-in excuse for failing to meet your target. But it is less likely to lead to the best times that you are capable of. Let me explain, and I emphasize that I mean no disrespect to Jason, I just want to suggest an alternative approach for those with a different mindset.
My background is in rowing, specifically on the indoor machine often called the "erg". We have organized indoor competitions attracting thousands of competitors, leading up to annual world championship races. I'm an ex-world champion in my age group, and until a few months ago held my age-group world record (65+), so I have some relevant experience. I'll never be a competitive bike racer because I'm too big and too old, but honestly I like riding on Zwift much better that rowing on the erg.
On the erg you have nothing to look at but the "power meter" in front of your face that shows your pace, both instantaneous and cumulative. Races are about 7 minutes long, so they are 70% aerobic and thus a little different from the 30-minute time trials that we are engaged in, but close enough that I think the same principles apply. Virtually every world record, and every championship race for many years, has been won by a competitor rowing even splits or negative splits (getting faster as the race progresses). Fly-and-die simply doesn't work, and I think there are two reasons. First is the exhaustion buildup in your legs, perhaps due to lactic acid or other reasons. You can ignore it in the beginning of the race because you feel pretty good, but it's happening behind the scenes anyway, and you will inevitably pay for it later. Second, there is a mental game going on and it's hard to exert yourself for very long at the edge of your capability.
If you have been riding with power meters for long, and testing your FTP, you have a very good idea of what you are capable of on a given day. Sure, there will be some variation due to "sensations" or your mindset, but the variation will be less than you might think. You will have more consistent results by riding with your power meter (the "Chris Froome" approach) vs. the how-I-feel approach (Alberto Contador). It's not as exciting but it works better because you disperse your energy in a flat power distribution throughout the whole ride, ideally ending up spent at the very end.
When I do a rowing race, which is 2000 meters, I usually break it into 4 intervals, looking at my time for the first 800m, next 600m, next 400m, and final 200m sprint. The first 800m is done at 1 second per 500m over my overall target pace. That makes it feel relatively easy, and almost halfway through the race I'm still feeling pretty good. Then I drop it to my target average pace for the next 600m. Third is 400m at 1 second below target pace. Sprinting at the end can shoot for 2 seconds below. This is not even pacing, it is negative splitting. It works for me because it minimizes my time in the "agonizing pain" zone.
This is harder to do on the bike because there is no cumulative power reading so it's hard to tell whether you are ahead or behind your target. Also there is a lot of variation in each pedal turn, unlike on the rowing machine which is pretty steady. But by watching the power readings continuously, or by taking times at various milestones, you can get a pretty good idea of how you are doing and adjust accordingly. This is why I think that taking a "watch the power meter" approach and try to ride even or negative splits will lead to the best times for most people. I urge you to try it.
