VO2 intervals: % of time HR above LTHR

I’ve read some people that recommend training based on HR instead of power, and getting your HR to 90% of max HR or above your LTHR if your know it.

I’ve got a good idea what my LTHR is, from a few different vectors.

Been doing Vo2max intervals, either 30s on / 15s off, or 3m on / 3m off. My time for heart rate above LTHR is significant;y below the time my power is spend in Vo2max. I know that the first ~90s of an interval end up being anaerobic before oxygen is depleted. The power to HR time disparity is quite large though. For about 10 minutes in vo2 power, I am seeing about 4-5 minutes where my HR is sustained above LTHR.

It seems most people talk about time in power zone when referring to vo2max intervals, so interested what others see for their time in heart rate zone that is above LTHR (or 90% of max HR) when doing vo2max intervals.

My worry is 5 minutes isn’t enough time and I need to find a way to dig harder and get more out of the intervals. My best was just shy of 10 minutes above LTHR, but this week, even with strong recovery (3 days of just 1h endurance and good sleep; recovery sore in 90%+ for 2 days) I only had HR above LTHR for about 5 minutes.

Or maybe I should just get my heart rate into zone with the first couple intervals being a hard start, and then just keep the intensity up and stop looking at HR for the rest of the intervals.

What do others see for vo2max interval HR zone time that they are satisfied with the quality on?

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Try no overthinking vo2 max. Go hard, too hard that you hold for whole interval, close your eyes and hold as hard as you can. Review after the ride.

You can also use Tim Cusick’s tip - after the workout, take the avg of your intervals (only “on”) part and start from there next time. With going as hard as I can, from 20 min of work, according to WKO usually 15-16 min is above 90% of vo2 max. Your goal is breathing and gasping rather than only HR.

With intermittent intervals I find a lot harder to achieve this.

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If time with HR >90% is your target then maybe try a different workout protocol…

I’ve been doing 4x8’s at max repeatable efforts and a single session gets me over 27 mins HR >90% in a 1hr 15m workout!

I like these sessions as I hate sessions where my HR goes >95% and most shorter vo2 type sessions (2-5m intervals) do that to me and things often go badly from there… I find the 30/15 type things also dont get that much time in the higher HR %'s. These 4x8’s get me to about 92-94% which feels like (RPE & breathing etc) quite a lot of time close to vo2 max.

Otherwise have a look at the Hard Start VO2 thread as there’s loads of good stuff discussed there.


I usually target 13 - 15 min in target HR zone per vo2max workout. I use a combination of time > 95% mHR, breathing rate (heavy) and RPE (must question life choices at some point) to evaluate sessions. I think you need to try all the different types and see what works best for you. Which kinda sucks. lol. I speculate that some of this comes down to individual VO2 kinetics / muscle fiber composition as to why certain protocols work better than others for individuals.

If I do 30/30s or 30/15s I blast my legs but HR doesn’t get above 80-85% mHR. If I do 3min @ 120ish% FTP only the last minute of each is in target HR zone, so 1min per interval. I implode around 8-9 intervals. If I do suprathreshold intervals it takes 4min to get my HR up, but then I can get 2-4min in target HR zone per interval, but I don’t know if breathing is as elevated as when power is higher.

Currently planning to experiment on ‘traditional’ 4-5min intervals as well as Bossi intervals (think threshold with pVO2max bursts of 20-30sec mixed in.)


Personally I find the longer intervals, 5min & 8min being the most effective for time spent above 90% of HR. I do them in “resistance mode”, and I try not to focus so much on power or heart rate, but rather attempt to shoot for the maximum sustained effort I can do across the intervals. The goal being my last interval power being close to the first. For a 3 x 8min, I find myself spending ~ 20 min above 90% of HR max.

The short 30/15s work too. But then I think it is important to execute them similar to how the Norwegian XC skiing teams does them. Push hard for 30seconds, and only allow yourself to recover a few beats per minutes for the short rests. Done that way, you will spend a lot of time above 90%

My LTHR is already >90% of my MaxHR so i asked seiler on twitter and recommended just “solving the equation” for myself. Just go hard, pay attention to your breathing(panting) and try to hold it for the duration