Forecasted training:
…You’re going to practice efforts near your max for extended periods to improve your performance on long mountain climbs. You should focus on very long efforts just above and just below your threshold…
Zone: 4 - Lactate Threshold. Target Interval Power: 337.5 watts.
and my FTP (according to Xert) is 286W.
I’m a bit buffled, should I focus on Z4/threshold intervals (and/or over/unders) then ? or on that 337W - which is 118% of my FTP.
These appear to be VO2 intervals. Your maximum FTP/TP is governed by your VO2, so by increasing VO2 you give more room for your FTP/TP to grow - as far as I understand it. So that is presumably why you have these in your training plan to ensure that your FTP/TP is not compromised by your VO2
for last months I was doing 12-15m @105%FTP x4 intervals.
My vo2max is quite high i guess (garmin reports 62, FTP 3.92 W/kg), also my HIE is high, up to 30kJ - I suppose from all vo2max work.
However I was thinking that maybe longer intervals at 95-100%FTP would be more beneficial? not to rely so much on HIE.
That target interval power is calculated based on the recommended Focus & Specificity of your training. We would recommend focusing on the ‘Target Interval Power’ value. For relatively short duration/high power efforts (2-6 min Focus), the target intervals probably won’t map all that well to Zones/%FTP since FTP scales so poorly in this part of the Power/Duration curve. In fact, this additional precision is what can make Xert more helpful for high-intensity efforts!
For example, for two athletes with an FTP of 250 W, one might have a PP of 800 & HIE of 17.0 kJ while the other might have a PP of 1500 W & HIE of 27.0 kJ. If we ask both athletes to target intervals at their unique 5 min power, the athlete with 800 W PP would be doing their efforts at ~305 W (122% FTP), while the athlete with 1500 W PP would be doing their 5 min intervals at ~337 W (135% FTP). So one athlete would be doing 5 min efforts in their “VO2max” zone while the other - doing the same relative intensity - would be doing their efforts in “Anaerobic Capacity” zone.
Hope this helps a bit!
I understand this ^^ 
but not this:
Zone: 4 - Lactate Threshold. Target Interval Power: 333.9 watts.
I was just curious why the text advice says about Threshold training (so 95-105%FTP), but Target Interval Power 118% FTP (I guess it’s my Target Focus ? (it’s mine 10mins power - climber focus), but it’s not Z4 and not threshold.
but, as I mention, I was thinking more about improving my FTP instead of HIE. (I guess I should choose Sprint time-triallist focus for longer than 10mins efforts?)