I would do it in either a race (40k TT) about 6 weeks about as an end to more FTP-based training before shifting to heavy distance or during the taper as a 20 min max.

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Endurance coach | Physiotherapist (primary care) | Bikefitter | Swede

I would do one when you know you are well rested, i often will do one 8-4 days before an A race since i am tapered and a good time to get some testing in. Depending how fit you are on the bike a 20min effort should not be hard to recover from.

Why are you looking to do a "last FTP test?" Don't your long ride/run bricks tell you all you need to know?

depends on your testing protocol, but 4-6 weeks is probably good. gives you some time to adjust your training zones and train accordingly. i wouldn't do it less than 4 weeks out - not for recovery issues, but more because you may not be adequately prepared to ride in your new zones (assuming your FTP improves).

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@adamwfurlong

The reason I want to do FTP test so late is I have been doubting my position since I rode a half Ironman 4 weeks ago and always thought the bike looked to small, anyway I went and got fitted (even though i got fitted last year) and the fitter put my saddle up
a whole 4.1 cm (wow) anyway i have been riding this week and feels good, very good. So my ftp at 75 percent has been set and done all the big days etc etc but now wonder if could be higher. I did Frankfurt last year in this position and to be fair I cant believe i didn't see it but that's my own fault.

I'd look to do one before entering the last block of your build. By build I meant he period where your really working on those race pace long rides, nutrition practice etc. no sense in deciding your going to ride at 70% of your ftp, working to a certain figure in training, then changing it 2-3-4 weeks before your race. Like gregn said, you should have a pretty good idea a decent way out because of the long rides and training.

Its pointless trying to do an FTP test if you are tired from IM training. You need to be rested. Ideally by now you should have enough faith in your numbers for the race, but it your heart is set on doing one do it in the taper. Use the numbers to base your future training on - not the IM race itself.

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He who understands the WHY, will understand the HOW.

4.1cm sounds like an awful lot. I would first question whether you went from maybe too low to too high. Second off your ftp isn't going to change that much anyway, even if it was too low your body is pretty good at adapting. I think you are overthinking the ftp thing - the majority of Ironman bikers bike too hard regardless of whether or not they know or have tested their ftp and are following a strict plan. You are better off just keeping it easy and smiling, if you can't smile you are going too hard.

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