Andrew, I’m curious to see what you think of block training, i.e. overload blocks of maybe 3-4 days consecutive days of higher intensity training followed by a few days of low intensity?
I find that when I do single HIIT sessions, with easy days after I don’t really make any gains, but when I block them together I seem to make improvements. The intervals in the sessions are usually around FTP or between FTP and VO2max, with relatively short breaks.
So day 1 is often 8x4 minutes around FTP with 1 min break. Day 2 is 5/6/7/8 minute intervals around 105% with increasing rest. And day 3 tends to be 8 minute intervals at around 110%. I often carb restrict and ‘sleep low’ after the final day, with easy session the following morning. Then 2 more easy days and back into it.

Seems to be working for me, as the building fatigue allows me to achieve significant overload, but I am sometimes concerned that I won’t achieve the adaptations if I’m too tired.

It depends.

Can you elaborate a bit :) Assuming I am a trained cyclist, and I want to continue to improve in 60 minute crits my training should in general look like......?

What Andy means is that what training is right for you depends on a range of factors covering an understanding of your physiological or power profile, previous performance data, what factors are limiting your improvement, what factors have you room to improve, your experience, race nouse and skills required for the goal events, your race program, the nature of the race demands (crits types can vary a lot in terrain and technicality), the race tactics and strategy best suited for you, physical factors (e.g. mass, aero), your logistical and other training constraints, motivational and other psychological factors, what you do in rest of life (e.g. desk bound vs intensive labour), stress levels, health/medical status, what your actual goals are (e.g. to win, to upgrade, to finish with the "A" bunch?) and so on...

We tend in these forums to focus on our effort during training and the desired physiological impacts but, in my experience as a coach, for racing crits and other mass start cycle races this is only one of several factors required for performance improvement and attaining goals. Indeed nailing efforts in training "perfectly" is not the most important factor nor is it that the most powerful that win, it's those who have the craft, skill, experience and know how to use their power wisely.

Yes of course we also want to be in the best shape we can be as well.

So even if we only consider the physiological aspect of training, well even that will vary over the course of a season so there is no one right answer as to what you (or anyone) should be doing right now.

It might be you are best served by a focus on lifting threshold power, or your peak power, or your sprint endurance, supra threshold reserves, or maximal aerobic power.

Who can say what will make most sense for you at this time? We simply don't have enough information to make such a call.

But whatever you do, just make sure the fun to work ratio is high enough for you. That's another cat that can be skinned in many ways.