Vo2 Max training - did I do it right?

After reading on some threads here/@SpareCycles blog/@empiricalcycling podcasts my understanding is that successful Vo2 max training is more about training the cardiovascular system than the muscular system. Today I did some 8 minute intervals for the first time with this new knowledge.

Last time I did them was back in April, and all I did then was focus on pushing the most power I could average for 8 minutes. Here is that workout in numbers (extended last interval to 10’):

Today I didn’t have power on my head unit. Instead just tried to elevate HR as quickly as possible to 95% of max and hold it for the rest of the interval. I also concentrated on keeping as high a cadence as I could. I noticed when it dropped I’d need to put more force out to compensate (and even then HR seemed to decrease slightly). Here is today’s workout:

It’s not quite as easy comparing the power numbers (as I was generally fitter, and with a higher FTP in April). The HR numbers are fairly comparable. The old workout was much more taxing (higher RPE and hurt the legs much more). But from the HR data I think today’s workout was better from a time at an appropriate HR zone (max is around 195, so 95% would be 185).

My heart certainly got a good workout today, but the power for the intervals seem so low that I really have to question if it was effective. Average power for all 3 intervals were below FTP. Is this really still training my vo2 max?


Cadence may be too high. Bring it down to 105-110rpm range. Intervals probably too long as well. Try 5x4min and see how that goes. 4x8 is more than 50% more interval time than I usually want to see from one of these sessions, with some rare exceptions. Hard to ay anything definitive without seeing a lot more data.


Thanks for getting back to me.
Do you mind me asking why it would be better to drop the cadence? was my understanding about the goal of these intervals being a HR focus rather than power wrong?
and these were 3x8’, I will definitely try some 5x4’s though. Along with 30/30s those are my bread and butter Vo2 sessions

Did your CV system really get a good workout? Or did the hard start/high cadence cause a greater contraction of plasma volume, thus elevating HR relative to VO2 due to a lower SV?

Triathletes should know what I’m talking about.

Something I’m curious about is lower power, high heart rate.

I race CX and ride single track on my single speed CX bike, which equates to A LOT of high force repeats and a lot of coasting, but a constantly elevated heart rate with a very very stochastic power profile. I suppose it’s similar to doing a 30/15 workout or something similar.

Here is a recent heart rate chart showing time in zones. I don’t have a PM on this bike so I can’t see the relationship between HR and PWR. But…

I assume this could constitute a good cardiovascular workout, but does one need to have more balance between power and heart rate or is heart rate alone a good determinant of taxing the CV system?

In theory, let’s say someone could ride with a cadence of 200 rpm @ 50% of VO2 max power. Assume their HR is @ Z6/VO2, but their power is well below VO2…would this be considered an effective VO2max workout?

It’s inducing more stress than is necessary. I’m sure someone has a more detailed answer.

From a cardiac-only perspective, it would depend on what is happening to SV, and hence Q. The only way to know for sure would therefore be to measure them (or VO2).

Certainly, just elevating HR alone doesn’t provide much of a stimulus. With circuit weight training, for example, you can maintain your HR at the same level as during continuous exercise, but VO2max doesn’t go up as much, if at all.


if you’re saying I didn’t target vo2 max, why is that?
and how should I correct that in the future?

If pure power isn’t the right target for a vo2 max interval, and neither is HR, what should you use to guide your interval training? in the real world, not in a lab setting. is it some kind of balance between the two? high power and a high cadence?

There’s a dropoff point with cadence where the extra energy cost to move your legs in space, shuffle calcium around, and especially increase effect of muscle pump, where you will not be able to do enough work to keep O2 demand at max. This is one of the big things in coaching these intervals: learning where someone’s max SV is and how to manipulate cadence and interval duration to maintain the stimulus I want to see. And as for the long intervals, let’s make the example extreme: if I ask you to do 3x60min intervals, you’re obligately at a lower work rate than if I ask you to do 3x6min. So getting into the 30-40 minute range for intervals, for most people, puts work rate lower than something where you can elicit the physiological stress I want to see.


Here’s how I look at it: if you produce enough power for a long enough period of time, you know what your minimum VO2 has to be. Otherwise, all bets are off.

this video implies the only thing that matters is HR and time at that HR. obviously youtube isn’t exactly the most reliable source of scientific information, but Tom Bell seems to be a fairly well established coach

I think it’s gotta be both.

Otherwise, how would one explain how running doesn’t really carryover that much into cycling, other than some base aerobic fitness, even though HR tends to be higher with running?

Also, the easiest way to boost HR is to increase muscle utilization, i.e. adding upper body. So why not train on an airdyne bike (with the arm rowers)?

I think it’s a combination of reaching that 90%+ HR zone, while doing it with the specificity of cycling.

Yeah a ‘VO2max’ or HIIT workout definitely needs to be performed at least somewhere above FTP. As long as it’s somewhere in the severe intensity domain, the precise programming is less important, IMO.

I prefer to prioritize duration and aim for something like 4x6+ min intervals. Again, as long as those intervals can be performed sufficiently above FTP (by that I just mean, not just like 5 W above FTP).

You can also prioritize higher intensity for shorter durations and more bouts. That’s where increasing cadence can raise the relative internal metabolic intensity a bit, while external workload remains lower.

I also don’t think a VO2max workout needs to be performed at 10/10 max avg power. Yes, you may not reach literal VO2max during the workout, but from everything I’m reading, it’s more about accumulating time near VO2max, ie. at high cardiac output, high stroke volume, etc. While prioritizing consistency across a training block rather than maxing out any single workout.

That’s my current interpretation anyway

What was your fatigue like for the rest of the day? The next day? Anything? Or did it feel like you didn’t perform a workout at all? That as well as anything else might be a reasonable subjective indicator of ‘effectiveness’.

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This is what I’ve come around to understand. There needs to be input (strain or watts into the pedals) that generates that output (Stress or HR). Otherwise how would you ever develop greater power @ VO2max. If it were the former one could find some sort of off-the-bike activity that maximized HR and time and just do that over and over.

Let’s not kid ourselves. All evidence points to the intensity itself as being a critical determinant of the adaptive response.

IOW, if possible VO2max intervals should be done at 10/10, as you put it. It’s just that most people lack sufficient motivation to go that hard on a regular basis, and doing so can be too stressful or can get in the way of other training. If your singular goal is just to raise your VO2max, though, then you do Hickson-style training, cardiac fibrosis be damned.

Curious what rest interval you would suggest for the 5x4 you mentioned? Also (and I know this is individual) in general what %FTP would you suggest starting at (i.e 110% and adjusting from there)?

Very true, but the evidence is more equivocal once we consider the difference between (eg.) exercise at 90% or 100% VO2max. Where the relatively small difference in intensity is made up for by a significant increase in sustainable duration. We definitely have to be working hard in the severe domain, but once we tick that box I’d argue duration at intensity becomes increasingly important. edit: and frequency/consistency of training bouts.

Another good point. I should say ‘to optimally improve your performance over time, my opinion is that you don’t need to perform every workout at 10/10’. To increase your VO2max on a test, you probably have to ‘study for the test’ and go to 100% VO2max more often.

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On what basis?

As I understood from the podcast series - start around 120-140% of the power you think you can hold for the interval duration for around 1 min as your heartrate skyrocket to the high level and then hold for the dear life for the rest of the interval (cadence around 100-110 rpm). You should gasping for air and think about not dying (but other part of your brain want you to die to end this suffering). And then repeat whole process.

I do not know if it is a extremely good example but from my understanding this should looks somewhat similar (probably with gentler power reduction after hard start). TR workout 5x4 min as a “rough” guide for me.

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4-8 minute rests should be plenty. I’ve never assigned a vo2max interval as a % FTP, and never will.

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