I've noticed that much of the training literature, as well as DVD coaches like Spinervals' Coach Troy, advocate training either in the range below 80% of max. HR (aerobic endurance) or above 90% (power), but to avoid the "no man's zone" in between.

However, I've also noticed that when I do a fast metric or a fast century, I tend to do the first part of the event right in that "no man's zone" and then kick it up to time-trial mode for the last 1.5-2 hours, finally going above LT for as long as I think I can do it.

So, if I'm going to ride for 1.5-3 hours in "no man's zone" anyway, why should I avoid training in that zone? Or perhaps I should rethink the way I dose my effort for these events?

Advice from fast century riders much appreciated.

("Fast" for me is anything under 5 1/2 hours for a century or 3 1/4 hours for a metric.)

Your lactate threshold could be anywhere between 50% (hopefully not) and 90+% (probably not) of your max hr. Your HR zones should be based on your lactate threshold HR, not max HR.

I end up riding at about 85% of my max HR for much of a century.

We don't normally train much in that middle zone because it tires one out and doesn't produce results proportionally. Thinking today is to do your endurance work at a level that doesn't exhaust you over time, and then supplement that with HIIT, which increases your ability to cruise at high HR more than anything else. Of course when you're riding an event, you use whatever HR is appropriate, without regard to training. Unless you're riding it for training, in which case you'd take it easy except for hammering the hills as hard as you can. I remember watching Boonen riding one of the spring Classics. He attacked again and again, only to slow down and let the peloton sweep him up. By the time they got to the last 10k he was too tired to be a threat, but he wasn't riding to win that race.

Sounds a lot like Lydiard ca 1950's. (not that there's anything wrong with that)

Good point -- I hadn't thought about cumulative overtraining that might occur with consistent efforts in that zone.

Even without thinking about overtraining, we need to be fresh enough to maximize our interval efforts. At the same time, taking time off to freshen oneself isn't helpful, either. It's a difficult balance. I do a bit of zone 3 training during base rides, like now, but that'll quit when I start preparing for the season, like March, because I'll start doing "low-intensity" intervals then. So that's kind of my rule: either ride some Z3 or ride intervals. Sometimes one's better, sometimes the other.

Well, whether you avoid the no man's zone or not is up to you. Any exercise that you do is better than any exercise that you do not do. If you like riding in that zone, do it. Even if it is not the most effective way to train, if you will do it, it is better than a training method that you won't use.

I am not arguing against doing the optimal methods, but if you don't like them, and will not do them then do what you like.

Given the range of abilities, experience, goals, training times, recovery times, and on and on, I'm curious what the single optimal methods are.

As is clear from the figure here, https://www.fascatcoaching.com/sweetspottraining.html, the response to training is a continuum; there are no discrete zones with step changes between them. There is no single right or wrong point on that continuum to train. The best choice will depend on all the individual characteristics and goals of each particular rider. The best we can hope for is to have the information and knowledge so each individual can design the best training plan for themselves.

You can train in that zone, I do once or twice a week at the moment.

The way I look at it is if you train in zone 3, or no mans land you are not going quick enough to make you quicker, but your not going slow enough to go long distance so your not really working one of the other.

So, I use zone 2 to train my endurance, circ 50 miles plus, and use zone 4 training for my speed work. When doing a sportive for example im no longer training so I use zone 3 as its a happy medium between speed and endurance, then up the pace near the end to zone 4.

This time of year I cannot get out so much due to bad weather so im limited to 2hr turbo sessions which is about as much turbo training as i can handle, and as I cannot go long I use zone 3 as it still gives the benefits of zone 2, but i generally take a day off, or do a recovery session the day after but it is possible to do back to back zone 3 rides.

That is a common point of view. It is also an incorrect one as has been explained earlier. Aerobic improvements come basically as the product of volume and intensity. This is illustrated in the referenced article.

If the purpose of your ride is to cause aerobic adaptations in slow twitch fibers than studies have shown 45%-75% vVo2max increase mitochondria to the same maximum levels the only difference from doing it at the lower end 45% is it will take longer.