Execution of 5x5 intervals at 125+%

Happy new year everyone!

I have a question that probably has been addressed before. In that case, a simple referral to that will be more than enough, tnx!

I have been reading and listening to you about the 5x5 intervals with 1 minute recovery, like podcast episode 129. If I understand correctly, you say that executing those at like 125% of ftp would not work/be achievable. However, that’s where I end up (or even a bit higher) if I want to make them tough. My most recent ftp test gave me 240 (and I’ve never had a higher result). I can do the 5x5(1)’s at 300+ watts. I’m always having a hard time keeping a steady power, but the average power for the intervals aren’t going down by the end of the workout. I can even crank it up a bit.

I (45y male, former 400m runner) know that I’m more of a sprinter/puncheur type and that my aerobic base needs work. Working on that base right now by including multiple zone 1 rides. But I’m wondering:

  • Should I bring the power numbers of the 5x5(1)’s down to perform these intervals with the desired training effect? Or can I just keep going like this?
  • Are the physiological/metabolic effects getting messed up by doing them at this intensity?

The past month training was a bit of a mess. I’m planning to do 2 interval sessions each week for the next 12 weeks, using pretty much the same 2 each week (with progressive overload in volume and/or intensity). I’m thinking to focus one on threshold and one on VO2max. Would 4x8(2) plus 5x5(1) make sense? Or maybe one of these and 30/15’s or higher power intervals like 3 minute with longer rest as the second workout?


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Your questions contain your answers. If you have an admittedly low aerobic base, work on your base. Should you tailor the efforts for the desired training effects? Absolutely. You say you want to make the efforts tough, but you should be striving to make them effective. I can tell you from recent personal experience, when you’re motivated you can do things in a workout that seem doable, but they’re not sustainable. Aside from there being no particular reason to do 12 weeks of high VO2 intervals, especially when you’re more likely doing anaerobic intervals in disguise, you will very likely dig yourself into a very deep hole of fatigue that will difficult to climb out of.

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Hi @Ilan. I asked @trevor this exact question last year and I think his answer was that you are using more relative anaerobic contribution at 125% FTP, when the goal of this interval is more aerobic. Could your FTP test be low if you can do 5X5 @ 125%? What FTP test did you use? I think I’m a similar athlete to you with a good anaerobic system from hockey, 47yo, FTP 245W. I’ve been doing two interval sessions per week and every 4th week is rest. Right now I’m doing 5X6min at 105% and 4X10min at 90% each week. I’m hoping this will give me good aerobic adaptations especially when combined with my long base rides. I’m going to progress towards 5X8 min at 105% and 4X16 min at 90% by the spring. Then I’ll add some Ronnestad short stacked intervals 3X13X30s15s for a few weeks before my first race.

First, Trevor’s 5x5 are FTP intervals not the traditional 5 minute VO2max type intervals. Trevor’s workout is an aerobic workout. The short rest periods keep you in the aerobic zone.

Why can’t you do them at an average power of 240? Put a 3 or 10 second average power field on your bike computer and then hit that target.

It also seems like your ftp might be under-assessed if you can easily hit 125% or more.

Tnx @Mudge, @robertehall1 and @AJS914 ,

You unanimously say it’s best to limit myself to the indicated percentage. So that may just be the right thing to do.

Regarding my ftp testing: when I started cycling more regularly and looking for more structured training early last year, I did the Trainerroad ramp test a few times with gradually increasing results, up to 235. In the mean time, Garmin and TrainingPeaks also gave some estimates, usually a bit higher than TR did. I quit TR before the summer, switched to Zwift for indoor riding last month and try to structure my training myself. Did the 20-minute test on Zwift last month, which gave me 240 (after doing less training for a while). There is a funny thing, though. I have a Xert data field om my Garmin Edge that estimates your ftp on the fly. That has given higher results quite regularly, even close to 280. However, those results were always when I did the higher intensity intervals or a few sprints. I’m pretty sure I cannot hold much over 240 for an hour.

@AJS914 , you write these 5x5’s are meant to be aerobic. Do you mean VO2max intervals aren’t? Aren’t they actually at the top end of aerobic intake (probably also using some of your anaerobic capacity if you push it)?

All this makes me wonder to what extent the VO2max may differ between individuals as an actual percentage of ftp. Wouldn’t people with high maximum oxygen intake and/or high tolerance for lactate have a higher percentage? Perhaps that is the case for @robertehall1 and me?

Even if that is the case, working on my aerobic capacity below that maximum does seem like a reasonable thing to prioritise…

I have been using Xert continuously for a year and find it quite valuable. Keep in mind Xert uses three metrics to define your capacity, not only FTP. So if you use the Xert platform for a while you may find your Xert FT is around 280, but your HIE and Peak Power are not where you want them to be. Using FTP only sometimes glosses over other areas needing improvement.

I just mean that Trevor’s 5x5s at threshold are purely aerobic and with the short rests, the subsequent intervals are even more aerobic.

VO2max intervals are going to be above threshold and include a lot of anaerobic contribution. (For example, WKO5 shows me that at my 5 minute power I have an 17% anaerobic contribution but at threshold, it’s 2%.)

@EG1, interesting to hear that. I only use the free data field through Garmin IQ Connect, but your input makes it interesting… My guess is that my LT1 is not where I want it to be, ftp a little less so while HIE and peak power (~1170) are relatively high.

@AJS914 Ah, I get what you mean now.

Something doesn´t sound correct here.
If you do 5x5(1) at 300 watts with 0 watts in the 1 min. rests, you will have an avarage of 258 watts for those 29 mininutes. The old rule of 95% of your 20 minutes power gives you an FTP of 245 watts if you take 95% of the 29 minutes.
How did you do your FTP-test? Have you done more than one?

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there is no correlation between 95% of the average power from a 5x5 session and an FTP calculation based on 95% of your 20 min power.