Proper VO2 workout inside HR or Power?

I’ve listened to podcasts on this, including the TR podcast and several others. I’ve not found a direct answer to my question. It seems that in a lab, or outdoors that a proper VO2 workout has your heart rate at 90-95% of max and power usually starts above threshold but by the last block may have moved down a bit to threshold or just under if the intervals are longer in duration.
But I’ve not seen much addressing less than ideal conditions indoors. Specifically what I’m getting on about is things like ventilation, body temperature, hydration, etc.
I’ve included screen captures of 3 workouts. Two of which were indoors, one of which was outdoors.
One indoor workout I did based on HR and basically got my HR to 185BPM which is about 95% of HR max and held it there decreasing the power.
A second indoor workout was done this week where I adjusted the power on the first two intervals to be a bit higher at the beginning but was still less power than my outdoor workout. The HR reached 192bpm where it basically sat there for several minutes in the workout. This is 98% of max HR. Yes it was hard, my legs hurt, I was breathing heavily but I was NOT about to die despite my HR being super high.
The outdoor workout is 4x5min with a couple of add’l shorter intervals at the end as the road allowed. Power was generally higher than the indoor workout, HR more controlled, but breathing harder at the end of the 4th interval. Legs were pretty tired at the end of the workout.
So this brings up a few questions. When I’m doing these indoors should be focused on power or HR? Some data suggest that HR above 96 or 97% of HR max for more than just a few seconds is COUNTER productive? In otherwords it pushes the heart and neuro systems too hard and blunts adaptation responses?
I am going to buy a proper fan at the end of this month for my indoor riding area, so I hope that helps with some of these HR drift that I have indoors, but I still need to know how to do a proper workout indoors to maximize adaptations.


Ignore HR, focus on power and breathing. Go hard and keep as long as you can. The first workout is plainly bad workout - if your power goes under ftp while doing vo2 max then cut the interval - no point doing it.

If you can hold 98% of your HR max for couple of minutes but then there is no very heavy brathing I doubt your HR max value.


For some individuals power targets wont get them to that maximal oxygen state (VO2max) but if its pushing your HR to 96/97% it sounds like it is or at least close to it. In your case ignore HR (it can be a variable metric anyway and who knows your maximum unless lab tested could be slightly more than you think) and hit your power targets or higher if possible and push to that maximal oxygen intake state.


This is not true. The body does not compartmentalize “zones.” What do people do in races? Usually start hard and then fall into “pace” (somewhere in the threshold/SS/Tempo realm). Efforts are more a spectrum or venn diagram than individual “buckets.”

Only time I would cut a workout is due to a steady decline in performance as the workout progressed. But there are workouts you do for a goal and then there are those you do for completion. In running an interval is measured by speed (hit a time for a certain distance). No doubt there are fluctuations in pace, power output, etc. Cycling is no different. Sometimes you just gotta get the work in and tough it out, even when things aren’t going so well. (This might occur in example 1).

As for the original question… OP, are you concerned that your heart rate increases though out the interval? If so that is normal.

I agree with @jarsson in that you need to ignore the heart rate and focus on power and breathing.


Empirical cycling podcast explain Vo2 max training, the why’s and how’s, very well.


I’m trying to understand the first workout. Assuming FTP and HR Max are reasonably accurately known, was it performed in a sauna while having espresso delivered intravenously?


Not saying about zones but from pure vo2 max training. Have nothing against hard start and then holding power - done some of those. I was just saying about pure vo2 max workout where you want to hold high power and hold it above anaerobic threshold. If your power is falling down as much there youax doing hard start threshold/sst workout - completely different thing than vo2 max focused work.


FTP and HR max are in the ballpark for sure. Long inside sessions my HR drifts quite a lot higher. I suspect this is heat/dehydration. I have only a very small fan. The room heats up quite a lot also due to body heat during the workouts. Room might start at 72 degrees and at workout end could be 80 degrees on a 2hr workout. With no ventilation it’s just a sweat fest, hence the buying of a new fan at the end of the month.


the studies on these types of intervals had cyclists doing max repeatable power, without regard to HR. And then some of the studies looked at HR during the last quarter of the interval and thats where they reported the majority were in 90-95% HRmax.

But the prescription on the studies I refer back to, they were “do max repeatable power” and its that simple.

Now when you use TrainerRoad, it defaults to Erg and % FTP. The instructions for many of TR’s 3+ minute vo2max workouts tell you max repeatable power, but its up to you to figure that out.


It defaults to what you left it in last now, which is great.

To the OP, those VO2 intervals don’t look like the right thing for your set of conditions in my opinion. If you are that severely lacking in cooling, I’d go for shorter intervals at a higher percentage of power. I find it easier to maintain power even when conditions aren’t as optimal then.

Agree with the others, don’t chase HR per se, check back after. Go listen to the @empiricalcycling VO2 podcasts, they really are the very best resource around when it comes to VO2 training.

Definitely the most effective are start hard, and hang on, at least for me that’ll send my HR sky high. If I end up below FTP though - to me that’s starting too hard, or dialing up an interval length that I’m not ready for.


To be clear the breathing at 98% of HR max, for example the one labled “indoor power”, is quite labored. There’s nothing easy about it. It was very hard, but also if I were outside my HR would probably have been 5-6bpm lower.

Indoor power is good vo2 max workout in my opinion. HR clamped not so much (as vo2max workout). If breathing is hard, hr high - good vo2 max. Ignore HR during the workout. And investing in the best possible coolong is always good investment.

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Shorter intervals inside are no problem for the most part, especially if done in the first 90 mins or so of a workout. 1min and 2min intervals are more than doable without my HR going berzerk. I’m hopeful the new fan will help a lot, when it finally cools off that’ll help a bunch too, we keep it cool over night in the winter so it’ll be 63 degrees in the room which makes a noticeable difference in my HR.

@jarsson that’s the conclusion I came to as well. While I was hot, breathing hard and tired on HR Clamped I definitely wasn’t that tired and my breathing was more in line with sweet spot vs VO2.

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Hey @TreyT :slight_smile:

Good questions! I’ll try and answer them below.

When I’m doing these indoors, should be focused on power or HR?

It would be best to focus on power instead of HR, whether you are riding indoors or outdoors. This is because your heart rate varies daily due to external factors such as stress, temperature, etc., and it is not a stable metric like power.

Heart rate is a reaction to work being done and not a measurement of actual work. For example, if you have a 3-minute interval at a power target of 200w, at the first minute, your HR may be 165, then on the second minute, it may be 175, and then on the last minute, it may be 185, but the thing is, you’re doing the same amount of work the whole time—200 watts.

The key thing here is to use heart rate as a complement to your power data as a way to tell a more broad story about your training rather than using it as a sole guiding metric.

Here is a nice article that goes more in-depth about why power is more reliable to use when training:

Some data suggest that HR above 96 or 97% of HR max for more than just a few seconds is COUNTER productive? In otherwords it pushes the heart and neuro systems too hard and blunts adaptation responses?

It’s hard to speak to this one due to the nature of HR :sweat_smile:.

The thing is, all-out efforts should be done sparingly since too much intensity can lead to injuries and extreme fatigue. This is why our training plans use Adaptive Training to progress you through your training with structured interval training to activate the correct energy system, leveraging your Progression Levels and Post-Workout Survey along with proper recovery to build upon your fitness.


from what i can gather, you need to focus on what the point of vo2 max training is. you are training or trying to get adaptions, to how much O2 the heart can supply. more oxygenated blood being delivered. the power hopefully will come from this, but you are trying to adapt the heart and blood mainly. so while you pay attention to high effort, high heart rate, you do NOT FOCUS on power. just go hard but dont sprint from 0 secs. certainly ride well above ftp to keep the energy demand high. you want to get heart rate up and sustain it with good power. rest and repeat. but don’t focus on %ftp and certainly not in erg mode.


Thank you.
Any thoughts/insight of doing two types of VO2 rides in a week? For example 30/15s one day and then 4 or 5 min intervals another?
This week I did a 12x2min VO2 workout and Friday I’ll do 4x5min or 5x5min VO2. Some stuff I’ve read, but from message board folks nothing scientific, says don’t mix interval types during a training block. Either do short punchy intervals or longer intervals for a full 3 week period. This is kind of boring and when inside I do better with 2 min intervals which is why I created the 12x2min workout.

This is mainly a coaching thing. If you mix interval types in a block then you can’t tell afterwards which interval type gave you improvements when you re-assess after the block.

If variety is more important than post-hoc analysis, mix away.


Who says don’t mix interval types?

It is common in the running world to do longer repeats (i.e. mile repeats) and then come back later in the week for 400’s or 200’s. A swiss Olympian I trained with did “straights and bends” (think 14s fast/18s float) pretty much year round.

I know cycling and running are two different beasts but the physiological training principles seem to parallel one another.


Hey @TreyT :slight_smile:

It’s fine if you want to. Our plans prescribe multiple different interval types each week often times!

However, I think the question is what is it that you are trying to accomplish by doing two types of VO2 rides a week?


Well in the off season it’s just about keeping my sanity on the trainer since our mornings can get quite cold and I must ride really early before work. It might make me a wimp but I don’t ride when it’s 20 or 25 degrees with howling north winds. 32 is about my limit because a 32 degree air temp at my house means the low lying areas will be in the low 20s. That’s plenty cold. If I go when its 25 the low lying spots will be in the teens and its just miserable.

So I’ll do indoor training for most of my hard rides in the winter during week. I get bored and don’t look forward to 4x5min or 5x4min for example. I find it much easier mentally to do 2min or 1min intervals, even if I do more work over the course of the ride that way, mentally it’s easier when I’m inside.

Outside I don’t mind 4x5min at all, I did it again this morning and it was fine. Hard but that’s the point. I just prefer to keep my sanity when I’m doing 8-10hrs a week indoors