Fractional Utilization of VO2 Max

I think the responses so far are on the right track, but I did have the following thought when listening to the discussion on the podcast:

Most people are using a proxy test for their FTP, be it the ramp test, 8min test, or 20min test. I find I get different results between the tests (although I haven’t done a 20min test for a long time), and to some extent I would expect the shorter duration tests might be more representative of max aerobic strength than hour strength. So if you’re trying to look at your fractional utilization to decide where your training should focus, would it not be better to calculate the ratio based on FTP derived from a longer (say the 20min) tests?

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In my personal experience yes or you can look at your power curve if you are confident you have gone full gas for different durations. Otherwise you are using a test that expects you have an average power curve.

I have a strong vo2 max and so get a much higher ftp if I do the 8 minute test, compared to 20 minute, maybe as much as 30 watts, ramp test gives me somewhere in the middle of the two. I did an hour at full effort as a test to check too because if I was going to make changes to my training I wanted to be sure. Fortunately the 20 minute test and hour give same result for me as long as I do a full effort for the 5 minutes prior to exhaust my vo2 advantage.

Fractional utilization of VO2max is nice to know and I look at it as one of many markers of fitness. But, it doesn’t change the methodology of training. The whole point is to move the line to the right. I can’t recall where I read it but, a well known coach said something like “training to increase FTP will invariably increase everything else along with it”. Meaning if you move your FTP say from 75% to 85% of VO2max I would your VO2max (power) and all other metrics will probably increase as well.

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After having completed SSBHV2 – which is 100% Sweet Spot – I did the ramp test and my FTP dropped 2%.

A bit disgruntled with that result yesterday, but today I think I’m more than ok with that result. Smart people correct my thinking if it’s not factual, but just from doing a couple outside rides, I would say all the SS work has increased my fractional utilization* even though i) the ramp test doesn’t display that, and ii) my VO2 ceiling has dropped due to lack of high end work.

For others who experience this, I propose two courses of action:

  1. up FTP to a reasonable level whilst lowering the intensity of VO2 workouts (if necessary). After a couple of weeks of raising the ceiling things should be back in line (better for Threshold work);
  2. go with the ramp derived FTP for all subsequent workouts and, as above, after a couple weeks of VO2 work the ceiling will be back to pre-SSB levels…but now with a higher utilization (better for VO2 work).

In either case, the next ramp test should see much more FTP improvement.

Although I’m training for a steady state race so maybe I just suck it up and live with a lower ceiling and higher utilization.

Time for more coffee. :coffee:

*(a quick scan of FUoVO2max research shows that weight lifting increases FU, in part due to increase in quad size and strength…which is basically what SSBHV does, just on the bike.)

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It might not be that simple, but I think there is something to it. I opted for Sustained Power Build because I was seeing strong gains in FTP without overemphasizing raising my ceiling (VO2 max) meaning I am focusing on filling the cup up first, then I’ll go back and work on making the cup bigger next Build.


Sounds plausible. That’s a limitation of relying on one test like the ramp test - can’t independently determine VO2 and FU.

Ideally, would do a 5 min max test to determine VO2max. And maybe something like the 20 min test to determine FTP. From there, you’d know both VO2max power, and FU.

You’d need a longer test than the 20 minute test to remove the effects of anaerobic contribution, even with the 5 minute effort ahead of time.

Ramp Test + a 35-50 minute test works great for me. Best of both worlds.

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It might, but i think i heard Chad saying that weights, and the additional muscle created, would be better at shuttling the byproducts of aerobic exercise away. And this extra muscle doesn’t need to be on the legs.
Additionally, re leg mass - it could be argued that to gain the same adaptation on the bike as weight training you’d probably need to be doing hard anaerobic intervals.

What do you take from the ramp test as power at VO2max?

Agree - longer than 20 mins better for FTP, it’s just harder :grin:.

Even though, a single 35-50 min test is easier than the multiple ~30 min tests in traditional MLSS testing!

Any chance you can review your Personal Records, via Seasons and Season Match, to see how you are doing no compared to other seasons?

Specifically, looking at power in the longer duration areas or simple Time to Exhaustion realm.

FTP is what it is, and a steady or dropped one is only one indicator. You may well have improved in other ares. I am guessing that the FUVO2 is one other way to look at the bigger picture, but the PR or other tests mentioned may help see where you are.

The long tests at threshold are a lot easier than the 20 minutes above threshold.

I use the 5 minute number from the Ramp Test and use the FTP from it as the test target for the longer test.

The 5 minute number is probably a little under what I could do all out, but it almost always matches what I can do for consistent intervals.


Just for reference, 5 minute power from the ramp test is always 121% of FTP, assuming that the test ended on 19:30 or close to it. I think that’s probably why the ramp test works very well for you.


Re your COAs. I’d go with No.1 and try to hang in there on the first few intervals on each VO2 session. I have found that the SSBII LV and Sustained Power Build LV has definitely increased my FU (quite a lot) but also my enabled me to complete the VO2 Max session at 100% (just!). If I were to focus on a VO2 dominated plan I’d use the Ramp Test to determine the FTP it is based on though.

As an aside for others…
For those who are reading this it links in with the thread I started below - but there are a few similar on the Forum now I’ve researched more. The first I’d heard of FU was when @stevemz replied to my post and it makes loads of sense and I really like Chad’s explanation on AACC Episode 189 at 31mins.

From post-SusPowBuild to post-SSB, my power curve rose from 12min onward, which is pretty indicative of the training I did in SSB. <12min was a dud. But I’m ok with that.


Thanks. This helps me identify when ramp test “fails” - the feeling for me is running out of air during the test. Looking at my last test a month ago, the ramp test resulted in 5-min power of 234W. After the test I manually set FTP to 230W which was good (but a little low) for threshold workouts, and relatively easy 60-sec vo2max efforts. That fractional utilization is a ridiculous 98%.

As a result of “running out of air” on the last two ramp tests, and guided with forum discussion on Coach Chad’s VO2max booster block, in February I did some vo2max efforts but was traveling and then sick. So not enough to call it a real block of VO2max booster work.

Despite “not doing enough” vo2max work, this past week my breathing was much improved on the Wed group ride and Sunday Crit. I did a hard 5-min effort as part of the early breakaway, and using that 5-min with my estimated FTP gives a far more respectable 88% (230 / 262).

After the Wed ride I cancelled General Build and replaced with Sustained Build. And yesterday based on the Crit I cancelled Sustained Build and went with Short Power Build. Looking at 88%, and knowing vo2max efforts are a limiter on both rides last week, looks like Short Power Build is the right call.

I like this thread. I’m digging into WKO5 and see that:

  • VO2max is modeled at 59 mL/min/kg
  • Power @ VO2max is 399w
  • mFTP 318w
  • FTP % of VO2max is 82%
  • FRC 23.9

If I’m understanding correctly, my fractional utilization would be 80% (derived from 318/399)

Wondering if that’s good, bad, other? Can I increase it? Assuming so, I’m doing a big block of LT/FTP work to drive LT/FTP up from the bottom with an emphasis on over/unders and interval sessions that focus on working at 125-150% of TTE (63 min). So 1x60, 2x35, 3x25, etc.

CX season is fast approaching so I won’t have time to do another MAP/VO2 focused block, but I’m really curious to see how I race after this LT/FTP block and then start applying high-intensity from CX races. I’m really hopeful it’ll be my best season yet.

To me the most useful application of that is to see what to do to keep pushing FTP. I think somewhere around 85% FTP is too close to vo2max to keep working on it, so you’d need to improve vo2max first. At least that’s my understanding of the theory. No real experience, as I’m rubbish in actually doing anything to see if it works…

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Very interesting thread here but I have a question… Earlier references to 6 of 3 minute repeats - what would the recovery be between those repeats? Would a workout like Mt Deborah or McMicken or Lerket be a good proxy for determining maximum repeatable vo2max power?

1:1 work:rest for VO2max/MAP intervals is common.

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Thanks @kurt.braeckel that’s helpful.