With the advent of direct drive trainers one would assume greater consistency and reliability with regard to FTP tests. If one uses the same protocol ,ie 20 minutes test or ramp test it should be the case after a few months to establish whether there is an increase or decrease or perhaps a stable FTP level of power output from the person being tested.

If this is the case, do any riders and especially distance riders ie, Audax participants have a notable performance outcome relative to their improved or decrease in FTP?

I ask the question as I'm interested to know whether one hour or so threshold sessions improve average power and thus speed over longer distances, say 100km or more.

You’ve got to also be aware of the power to speed relationships. The amount of power required rises in proportion to the cube of the speed.

The following are from an online calculator based on a drop bar road bike config

For instance maintain 100 watts on flat and you’ll get approx 24 km/h

Add another 50 watts to 150 watts you get approx 28 km/h

Add another 50 watts to 200 watts you get approx 31 km/h

Add another 50 watts to 250 watts you get approx 34 km/h

So whilst you may see ftp increases that in itself may not translate out on the road unless the increases are substantial. You also need to wary of ftp tests being very short, which means you may get a non trivial anaerobic contribution , inflating the figure.

Interestingly there’s a paper out there that says there’s a significant correlation between fat oxidation levels and iron man performance. The best athletes their fat oxidation at 250 watts as at least 90% of the value at 100 watts. The others are purely glycosis by 250 watts. This is independent of Vo2 max. High intensity won’t develop your fat oxidation capability. For that you’ll need to add the long duration low intensity rides as well. Plus diet on top if you want.