Does anyone do any "pre-fatigue" work before doing a 2x20 Threshold Interval session?

I recently took my first (20 min) FTP test using Andrew Coggan's protocol. The protocol required a 5 minute all out effort before settling into the 20 min test effort.

My current training plan requires 2x20 Threshold Intervals. Do I need to do a 5 min all out effort as part of my warm up before starting the intervals?

It’s not necessary but it won’t hurt. I often do a 10min warmup followed by a hard 5 min and then 5min easy before starting a 2x20 on the trainer. Mostly because I want a little more than an hour in duration and I can get an idea of how I'm going to feel after the 5min interval.

Yeah, you should warm up by exceeding the stress of the steady-state you are about to experience. I usually do 2 reps of 1.5 minutes full throttle with maybe 3 minutes between and after. But some sort of warm up will help a lot.

No. The point of the 5 min all out on the test is to better estimate your 20 minute power. Those with higher anaerobic abilities can use those abilities to get through a 20 min effort and end up with a higher estimated ftp number than those more aerobically inclined. Hitting that 5 mins all out forces everyone to rely more heavily on their aerobic fitness for the 20 minutes.

Trying to do that before a workout is going to kill your workout. A true 5 minute max effort will leave you struggling to complete one 20 minute effort, let alone two.

So yes, it will hurt and no, you shouldn't do it.

Doing a couple of minutes at ftp or slightly above to ensure you're properly warmed up is generally good, though.

Yes, that's my understanding also, and I agree that doing a hard (threshold) 5min, but not all-out, effort before a recovery and before the first 20min interval is a good idea just to get you ready to work.

Or use friel's 30 min FTP test averaging the last 20 mins.