Using HR during VO2max workouts

[Robert_M_Skalecki]

I’m fairly new to structured endurance training, and I track HR along with Power, but I’m struggling to effectively use HR for anything other than post-workout analysis.

My main difficulty with HR is that it is a severely lagging indicator of effort. I’m try to hit HR zones when doing VO2max intervals, but I don’t know if I’m actually hitting my target until the end of my interval. If the intervals are short, I usually won’t know until the end of my second interval. So, basically, I’m just using a combination of RPE and power to get in the vicinity of my target and looking at the HR later to see how I did.

Is that the way everyone uses HR for intervals? Training to RPE and adjusting RPE based on HR feedback at the end of each interval? Or, should I try to learn the pattern of my HR response so that I can adjust effort during an interval (at least longer 4-min+ intervals)?

I do enjoy using HR as a sanity check for my Zone 2 efforts, where I’m mostly just looking out for HR drift. I use the talk test and power to set the initial effort level. It’s the efforts <10min that seem so difficult to calibrate with HR.

[Chris1982]

Hey Robert, I see you joined Feb 4, unsure on your experience level w structured training, based on power or HR zones.

I’ll forewarn you that you’re going to get many extremely contrasted opinions, many with ‘studies’ , that may or may not have valid methods, N = sometimes literally 2 - 10 participants, often in a tight range, such as, ohhh, I don’t know, at random let’s say something like “Five males 24 - 29, pre-trained cyclists with an athletic build & BMI.”

Take all w a massive grain of salt, including me !

I’d been riding abt 5 - 7 yrs, outdoor rides, unstructured trainer, and Zwift racing. Started structured on TrainerRoad, and bought in 100% to power - only based training.

Went amazing @ first, got the legendary ‘n00b gainz’, but blew up, overcooked my legs, and had lots of DNF WOs and many skipped WO days once I got into Thresh & VO2 work.

Like many around here, I’m super A type, science background, so I dug into things.

I spoke w some coaches who have brought professional athletes to gold at world champion events, and also some athletes who won events at that level.

The angle they shared is that hard-set power or HR zones work well for other work, but for Thresh & VO2, it should only be RPE.

Because we know our output can vary so much day-to-day due to sleep, nutrition, stress, it makes no sense to hard-set a number that is then preset by the trainer, that you must hit, or you can’t complete the WO.

If your “Thresh” is 240 w, but one day at 5 - 9 RPE, and you just can not get it over 220, it’s much better to stay there, complete the WO, load in that training stress, benefit from it, recover, and continue to nail your TP 100%.

For VO2s, especially when ppl are new to them [ myself incl. ], when doing a 4 x 3 min set, your first int will almost always be at a higher w than your last.

This is what happens, if you really are nailing a great VO2 interval in your first one. And by allowing yourself to rip by RPE, you’ll still get 3 mins time-in-zone on your last interval, and a great quality WO.

They key is to pick a power that you can hold consistent for the entirety of each interval, as close as possible. Don’t blow up; if it has to drop slightly to finish the int, it’s fine, but if you have to drop it a lot, you picked a starting power too high.

It should take you a couple WO of finishing saying “I could have gone out harder.” before you get it all dialed in, and know exactly how your bod can do VO2s best, what your targets should be, etc.

Power is just for ballparking, and HR is only for after analysis, as you said above. As long as RPE is good, and you’re not going to yak, do not drop output because HR is “getting too high”.

Have fun.

[Lukasz_Pludowski]

For anything above LT2 I would use power and hr only post workout for assessing your overall fatigue for example. (if your hr has hard time reaching your vo2 it is very often due to lack of rest and high chronic fatigue.)
If you want to push your body into your desired hr range you can structure your vo2mqx workouts with some hard starts so instead of doing 5x4min@360w (numbers just as an example) you do 30-45s at 380w and rest at 350w or so the avg power stays teh same but you reach desired hr faster.

I was always doing vo2max intervals by power and it was always 3rd or 4th interval really fully at a correct hr zone. Actually the hardest thing about planning vo2max intervals is to chose power where first two are kinda easy to ride, 3rd is pretty hard, 4th is crazy hard, and 5th is impossible and you finish it only because you know you can go home afterwrds (all intervals at the same power). you plan them 10w to easy and they are all too easy, and 10w too hard and 3rd is impossible to finish.

so in short I would give up on checkig your hr for anything above threshold. RPE is ok but like the easiest way to say your vo2max intervals were done correctly at correct power is if you really ask yourself during 3rd and 4th interval what is the point of this shit and why are you even doing this to yourself. There is not much tinkering here. Vo2 is really hard to complete mentally bc you are wandering to the place where you body has no will to be at all and will do anything to stop you from going there (hr close to maxhr are reserved for really critical situation)

[fabric5000]

I"m going to largely echo Chris and Lukasz here, they hit all the big points. LT and VO2 max intervals are about practicing so that you can complete them with the last not being all that different from the first. RPE is key. and they are both right - the first few should seem easy. If the first one felt hard - you probably went out too fast.

That being said, I use power a lot for both of these, and I reference HR during as well. Here’s how I manage my intervals:

There’s a reason it’s a zone, and not a number - none of this is exact. If you are confident your FTP is reasonably correct, the middle of the zone is a great place to start your first interval. And then see what your HR is at the end of the first interval. If you stayed at around that middle power number and the HR hasn’t gone out of that zone by the end of your interval, you’re probably in the ball park. Now you can be reasonably confident that you have a number for this workout that you can use to help keep you from going too hard or too easy. And remember -your RPE is going to go up over the workout. If the last interval isn’t at least a little harder than the first couple, you’re probably going too easy. Particularly for VO2 max. Lukasz has that right for sure on the last Vo2 max interval! Ugh!

So that was an everything is going well interval workout. Now how about the other times? Power is high, you feel great, RPE seems right and HR is high? Probably ignore the HR and just keep going. same but HR is low? You might be tired, maybe dial it back to the middle of the zone? If power is good, RPE is good, HR is probably not all that helpful.

Power is low, RPE feels right, heart rate is about right? I’d probably stick it out at the lower Power, unless it’s way below your zone. If the HR is high or low, this is when you might consider doing another interval or 2 and see how you feel.

RPE is way high? This is probably a bad sign. if you can get the power within the zone and the HR stays in the right place towards the end of the interval, this might be when you suck it up buttercup. Drop the power a little and just keep going. Or it means you need to pull the plug. I’d probably pull the plug in this case, and definitely have. I"ve also done this for a zone 2 workout. RPE is the first, most important thing here.

Wait Chris - didn’t you just tell me I’m training too hard? You still probably are! But when it’s time for a hard workout - you gotta do it, and that means it’s gonna be hard! You need to make the hard work count. Just be smart about it.

[WindWarrior]

Training by HR (no power meter) can work well at threshold and below. My power-to-HR is pretty reliable and predictable. So training by HR works well for me to do long tempo and endurance. Also for longer threshold, although it can take 5-10 minutes for HR to convergence on LTHR.

Above threshold its max effort.

[Chris1982]

Lots of good chat & info above.

Going to double down on what I said & also echo what Wind is reinforcing; above Thresh, it’s RPE only, and all - out.

Going to expand on that; I believe Wind & I are saying the same thing here: It’s all - out effort for the target effort; be it a VO2 int, anaerobic 20 - 40 s burst, or 5 - 15 s sprint.

Meaning: If you’re doing 4 x 4 min VO2s, you’re trying to pick a power number you can hold for that whole 4 min int, on each. You’re obvi not literally going all - out, max sprint effort. But you are going as hard as you can hold, for that 4 mins. Regardless of the next one. On the recovery int, you decide; same power on next ? Bit higher; you undershot it ? Bit lower; you know you won’t finish 4 mins there again ?

During the int; drop as necessary; but only if necessary.

I believe Fabric is saying the same thing, in a different way; that you adjust by feel, but also use power and HR as informers, to rough guesstimate targets on first intervals of a set, etc. As in while I am going to go all - out for the int, I use power to ballpark where that will be; I know damn well it’s not going to be 275…

Some examples, to share info & results:

-If I had tried to do 250 on all 4 ints, I would have failed this WO.

-But, on the first, I was gassed up, and that is what I felt I had in the tank, for that full int.

-I failed the first int; I couldn’t hold the 250, had to drop it around 2:45.

-If I had held back based on power - set zones, to 215 - 230 ish, I wouldn’t have maxxxed out my HR as nicely; I would have sailed through that first int… zero TIZ in target zones… and true muscular VO2 power output…

-If I had held back bc my HR was “getting too high” , I wouldn’t have really been nailing what I totally could nail, at reasonable RPE, and an output & total WO stress I can properly recover from, before the next WO.

-During the rest int, I knew damn well I couldn’t do that again; readjusted.

-Because of all above; I got excellent TIZ in all 4 ints, and an overall great result.

-I post-analyze w HR, but it’s retrospective info only; a gentle “Yep, cool, rocked that one !”

Here’s one a while later where I was tired. I knew damn well I had to drop the targets. Again; if I had been nailed to a set power target by my trainer, I would have failed this WO; wouldn’t even have finished my first int.

Because I adjusted, I really nailed this one, and HR for all 4 ints confirms that; I was really cooking @ my max.

When I first started self - set VO2 ints, there were a few rough ones where I fell apart in some ints by overshooting it & blowing up.

The cool thing is; I can keep having that happen. If I miss my target, or overshoot, you just drop power, keep in your max VO2 output that you can manage in that moment and finish the int & WO. You don’t just fail out.

NOT an expert and still TONS to learn.

But I really think the switch btwn power - set, or HR - set VO2 ints, and doing self - set, all - out efforts every time is one of the most valuable things I have ever learned about training.

[fabric5000]

@Chris1982

Going to expand on that; I believe Wind & I are saying the same thing here: It’s all - out effort for the target effort; be it a VO2 int, anaerobic 20 - 40 s burst, or 5 - 15 s sprint.

Meaning: If you’re doing 4 x 4 min VO2s, you’re trying to pick a power number you can hold for that whole 4 min int, on each. You’re obvi not literally going all - out, max sprint effort. But you are going as hard as you can hold, for that 4 mins. Regardless of the next one. On the recovery int, you decide; same power on next ? Bit higher; you undershot it ? Bit lower; you know you won’t finish 4 mins there again ?

During the int; drop as necessary; but only if necessary.

I believe Fabric is saying the same thing, in a different way; that you adjust by feel, but also use power and HR as informers, to rough guesstimate targets on first intervals of a set, etc. As in while I am going to go all - out for the int, I use power to ballpark where that will be; I know damn well it’s not going to be 275…

I think we are totally on the same page here and it’s just one thing in your wording here - “as hard as you can hold, for the 4 mins. regardless of the next one” is having me confused but everything else you’ve written here we seem to be in agreement that all the intervals should be substantially equal in power. Which is totally what you are doing in your illustrated intervals!

And your last comments are right on as well. My Z3, Z4 and Z5 zones are 40 Watts across! You didn’t fail your workout if you didn’t keep them all at exactly the same number.

I’ve heard a few coaches talk about using the performance of the intervals as the determiner for the number to do! Just keep doing them until you have one that doesn’t go well. I’m a little too type A to be that flexible. This is also how some weight lifters do it. They pick a weight and number of sets, but the reps are done by feel - to some reps in reserve or to failure - but not to a specific number.

I’m hoping newer cyclists are finding this useful, these are great discussions! The right workout is the one that you’ll do. All these studies with specific intervals and zones and execution - these are all simply things that have been studied that need rigorous protocols and show results based on statistical significance. But if you look closely at the individual results of these studies - they are all frequently all over the place. 1 athlete sees a 40% improvement, 5 see a 10% improvement, 2 see no improvement, 1 sees a 15% decrease.

AFAIK all of this is a starting point for you to try different workouts, see what you like, see what makes you improve.

[Robert_M_Skalecki]

Thank you all for such thorough answers! I’m very glad that the discussion drifted into general recommendations for training above threshold, because I have a lot to learn there.

What I’ve gathered from this conversation is that targeting a HR for intervals is not effective, and that data should be used in post-analysis to verify that the workout was at approximately the correct intensity level. That makes sense. I think I was misinterpreting something I had read earlier about the goal of VO2 max workouts being to spend time at a high HR zone rather than a high Power zone.

Now comes the hard part of figuring out how to make it through a proper VO2 max workout without failing physically or psychologically.

This morning I tried to do a four by three minute workout in the spirit of the workouts that @Chris1982 kindly shared above. And the results were enlightening. I absolutely smashed the first interval (set a new 3min power record and held steady for the exact target duration). However, I felt wrecked and did NOT want to do more intervals. I gave myself an extra minute of recovery and hit the second interval at significantly lower power (which I let demoralize me). At the end of the second interval, I got a message from work and have never been more willing to cut a ride short!

Looking at the chart, I think things were going fine, and my problems were purely psychological. My actual power in the second interval was not as low as it seemed during the ride, and I was still getting a good HR response. I think the main difference between the two intervals is that I burned off a bunch of my anaerobic reserves in the first. When I give it all another try, I’ll focus on being more positive about my late interval efforts, which I hope will give me more will to fight through the awful fatigue.

[WindWarrior]

@Robert_M_Skalecki

What I’ve gathered from this conversation is that targeting a HR for intervals is not effective, and that data should be used in post-analysis to verify that the workout was at approximately the correct intensity level.

Personally for 3+ minute intervals I use power to adjust intensity up/down, and seek to feel my breathing. After 2 minutes I should be breathing heavily and uncomfortable.

FWIW from February

W’ you can see I nearly emptied the tank on the first interval. Maybe backed off a little too much on intervals 2-4. At the start of interval 3, the legs felt heavy and so I skipped it for some additional recovery.

From a couple years ago, where I mentally abandoned the 4th interval:

It’s also possible to hit max aerobic (vo2max) on shorter intervals, like this 16% monster in January. It was at the top of an HC climb:

Took about 5 minutes for my breathing to recover, probably the heaviest breathing in 3+ years.

[Chris1982]

@Robert_M_Skalecki great work on your “First Real VO2 WO” !! You did a hell of a lot better than I did on my 1st couple !!

The first couple / few times, you’ll likely “fail” = not finish the full 4, but this ain’t failure; it’s learning. You’ll get a full 3 - 4 ints quicker than you think.

Keep it up and check back in after a few, let us know how it’s going.

Hopefully after the WO, esp seeing your power in the 2nd was better than it felt, you thought & felt "Wow. I got a pretty solid two intervals, that felt more legit VO2 than they used to."

I’d echo what Wind said above; you are glancing at power to dial in your targets for each int. You’re just not holding anything back, if RPE is solid. Going all - out. But yeah, totally using power as an indicator / rough guide.

You’re also not saying “Ok, I have to hit 230w no matter what RPE is, including if I blow up and fail.”.

[fabric5000]

Yup, VO2 intervals are an interesting pacing exercise.

Based on a 280W FTP, I’d say you did go out too hard on that first one. 360NP for 3 minutes is a lot! Your very first VO2 interval should feel “easy.”

The screen I have up during my intervals lets me easily see my power while avoiding the interval time. But I do still leverage the time. I personally find that if I’m doing them right, for the first 2 intervals when I feel the need to check how much time I have left, it’s often only 30 seconds. By the last interval, I might end up seeing that I still have 2 minutes left.

You’ll start finding your own tricks to help you get through them more effectively.

[Chris1982]

@fabric5000 is that really true; your first int should feel “easy” ?

The method I’ve been following is all - out, on every int, incl the first. Meaning you’re already @ RPE 8.5 - 9 @ the end of that int… ideally by the one - third to halfway pt.

This, for me, bc I’m not a v strong rider, and repeatability / W’ / fuel tank over Thresh is quite small, automatically means that each successive int will be slightly lower W.

I would sincerely appreciate everyone’s input on this. @WindWarrior included: Am I going to hard, and the target should be much closer W matching between all 4 ints: Your legs & cardio systems are truly in VO2 if you’re putting out those Ws rel to your FTP, and RPE just will be lower on int 1 - 2 ?

I was under the understanding VO2 comes from muscular O2 consumption zone; aka muscles must be in dire straights, maxxximal O2 consumption & demand, so RPE must be 8.5 - 9.5 to be in VO2… and your systems are just able to crank more in int 1 - 2, bc they have more reserves / energy to fry at first…

Thank everyone in this thread, incl OP, for your time. This is really excellent discussion and sharing of informed actual long - term experience, and I sincerely appreciate it all.

This type of info has been the greatest accelerator to my growth as a cyclist, of all the books I own, sci journ articles I’ve read, etc.

[Robert_M_Skalecki]

I did another session of 3-min intervals today. I aimed for and completed three intervals, because I was both somewhat short on time and also wanted to set myself up for success after achieving only two intervals last week. I completed the planned workout and I think I now have a better feel for how these should go.

Despite, @Chris1982 's encouragement that all intervals should be done right to the limit, I decided to back off the first interval ever so slightly, hitting 359W instead of 369W. That’s still over 128% FTP, and I would not call that first interval easy! But I was not wrecked, and I could have held the power longer. My recovery felt significantly better, and I was able to hit 350W for both of my next two intervals. Both of those intervals felt pretty hard, but I think I could have given just a little more. A fourth interval was definitely doable.

Here is the workout:

Lessons:

• Easing off slightly in the first interval (not going to absolute failure) significantly improved both my power output in later intervals and my morale throughout the workout. I’m not sure how important the first is, but the second was greatly appreciated.
• Knowing how everything will feel through the interval’s progression is very helpful psychologically. My legs are going to be very angry for the first 30s (ignore them!). The ramp in breathing will feel unsustainable around the half-way point (it will level off). The last 30s will suck (push through!).
• Don’t do this on uneven terrain! Constantly shifting through changes in gradient made the process of holding power needlessly difficult.

Next week I’ll go for four intervals, and hopefully everything will come together.

[Chris1982]

@Robert_M_Skalecki this is spectacular in - the - moment internal thought processing !! 100% agreed on all above.

I’m strongly considering backing off from 100% on the first int going fwd…

[ Adding: I strongly think power spikes cause an immediate & temporary cellular extreme buildup of heat & undesirable chem byproducts, and extreme deficit in O2, Glu & other goodies, creating micro - extreme stress & fatigue.

Hence the “… legs are going to be very angry for the first 30s ( ignore them!)…”

I choose not to ignore them. I’m a big baby, maybe ?!

I ramp to 100% over the first 30s. I’m 95% sure this lets me get more TiZ & positive stimulus instead of detrimental muscular extreme stress, recover better, and have stronger repeatability in future WOs on multi - series VO2 blocks. I leave the sudden power spike stress for race days. 95% sure it’s nothing but detrimental additional stress wo benefit… I’m not 22 yrs old anymore… ]

[WindWarrior]

@Chris1982

I would sincerely appreciate everyone’s input on this. @WindWarrior included: Am I going to hard, and the target should be much closer W matching between all 4 ints: Your legs & cardio systems are truly in VO2 if you’re putting out those Ws rel to your FTP, and RPE just will be lower on int 1 - 2 ?

I dunno. Some of my best 3-min efforts are hard start (761W peak) like this:

during hard group rides.

On those hard group rides I often collect more time >90% estimated vo2max (WKO5) versus intervals like this:

both have their place. In general, personally I need more hard start efforts because I’m bigger, not that aero, and have a lower W/kg versus a lot of other riders.

For interval work like 4x3-min, I tend to go with max repeatable power and as high cadence as possible.

From a physiology point-of-view, hard starts create a huge demand for oxygen in the muscles and therefore you will reach vo2max earlier. High cadence also helps in driving higher demand for oxygen, and with muscle pump preload that helps with returning blood to the heart (if I remember correctly). If you are interested it is worth listening to Empirical Cycling’s podcasts on vo2max.