Question: %VO2 max definition

I caught this 90% VO2 max magic threshold in a couple of threads. What does that mean in actionable metrics? And why is the relationship between VO2 max % and MHR % out of whack; in that 100% VO2 max is > MHR? I mean I guess it makes a sort of sense if I am thinking about anaerobic contributions or am I barking up the wrong tree here.

The fact is I am struggling to hit some of the projected HR zones ~95% MHR before the breathing and legs crap out of a given interval. HTFU?

Wrong tree.

Ignoring factors that would “artificially” elevate HR (e.g., heat stress), MHR and VO2max should occur essentially simultaneously.

At any intensity less than that, though, % of MHR will be higher than % of VO2max, because at rest you are at perhaps 25% of MHR, but only about 5% of VO2max.

Your experience with difficulty getting your HR up during intense intervals is quite common. It can be due to fatigue, insufficient motivation, poor pacing, etc. Lack of cycling-specific fitness can also play a role.

First question, how do you know your MHR is correct? Maybe it’s dropped a little and what you think is 95% is actually 98% - I wouldn’t want to go there repeatedly!

The other part…I’m not sure HR and VO2max are that correlated. For one, HR has other factors that influence it, there needs to be room for them to shift it up/down. And then VO2max has to do with oxygen transfer, when that is maxed out, there is no need for HR to keep increasing.

I’d say yes - there is this study that showed that once you reached VO2max, you can back off a bit, and still stay there

I’m deffo not an expert in this though, hah!

Yeah I agree. I can never decide if you actually need to go that hard. On one hand I think that most of these training effects happen on a continuum, so if you ease of little bit, you should still get nearly the same benefit. On the other hand there is this thing that when you want to progress anything “max”, you need to actually go “max” (like lifting power or a sprint) - but then you have to do it rested to be able to do it properly.

This is definitely NOT true for me. Unless by VO2max you mean some theoretical absolute maximum oxygen consumption that nobody can ever attain but is calculated in a spreadsheet. Anybody else have actual measurements of oxygen consumption compared to heart rate & can confirm refute this? Interested to know if my experience is similar or different from others.

Again, if we’re just talking about some non-practical theory…ha! Then we can bin the discussion. Doesn’t matter.

I recently read sparecycle’s blog with some data, including VO2 about this type of hard-start intervals. He’s saying to aim for 90% MHR.

Not following what you’re saying here. 90% of VO2max, while a legit metric, would be hard to implement as a practical training protocol. Most people don’t really have a way to keep track of 02 consumption real-time during a workout…and if they do it just plain sucks to work out that way. Even if you’re using that tubeless VO2max mask.

Also, ‘100% VO2 max is > MHR?’…if MHR=max heart rate I don’t think anything can be ‘more’ than a maximum unless that really wasn’t a maximum. But in any event you don’t have to be at max heart rate to be at maximum oxygen consumption on the bike.

Maybe it would be a good idea to find somebody who can measure your oxygen consumption & just go fiddle around with some intervals/ramps so you can get a feel for what VO2max feels like. That helped me out a lot. For me, I found out that VO2max was a lot HARDER than what I had been led to believe. Those Billat intervals are not VO2max…three minute VO2max intervals can be but for the most part, those aren’t either for the first few intervals.

Never paid super close attention to heart rate except to say oxygen consumption definitely reaches a plateau BEFORE heart rate approached what would have been the highest I’ve ever seen on a bike. Like…maybe 10 or 12 beats lower than what would have been ‘max’?

Well, I don’t know…that’s why I ask. Is this everybody’s experience? I know for me oxygen consumption maxes out at a heart rate that is well less than what I would consider a maximum. But maybe that’s not everybody else’s experience? Let’s hear from people that have done it…what did you see?

I would need more information to really comment, but I can say for a fact that what you report would be quite unusual.

In fact, it implies a significant degree of left ventricular dysfunction, e.g., due to ischemia, such SV falls markedly as you approach VO2max. This would necessitate a compensatory rise in HR to maintain/further elevate Q. (A-vO2diff widens during exercise, but is already close to maximal at submaximal intensities.)

Yikes!

I was just reading through the paper that I talked about in my ‘Anatomy of a 15 minute Vo2max interval’ post’ Looks like the subjects in that paper have the same problem I do! I wonder why such a uniform sub-set of athletes are experiencing a plateau in oxygen consumption previous to reaching max HR…especially if it’s so unusual? Maybe it’s the type of workout we’re doing…

Maybe for some but not for me. I got to a point where oxygen consumption no longer increased at a HR that was about 12bpm less than my max HR. So maybe I’m unusual in this respect.

Also, maybe more argument just to go do some VO2 work with a mask on & see how it feels. Not to spoil it but it feels like crap & it’s made even more uncomfortable by having a tube jammed in your mouth and a clothes pin on your nose. :smiley:

Cycling MHR is probably a bit lower than absolute MHR. But then so should be oxygen use…

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Thanks. Yup, I’ve said that. And honestly now I would back up a step and just say “go 9/10 effort”, whatever that means to you, however you want to quantify it.

From what I’m reading and working on, I would suggest that we don’t need to max out intensity (VO2max, HRmax, Wmax, 10/10 RPE, whatever) in order to see improved performances a few weeks down the line. Consistent training in the target intensity zone (again, however you want to define that… just be above threshold) should be the main focus. Details beyond that are definitely important, but impossible to generalize. Applies to well-trained and recreational athletes, but your results will vary.

I’m very happy to debate (in good faith) the question of how close to 100% intensity is necessary! I think the answer is slightly lower intensity (as long as still within severe domain) in favour of slightly longer interval duration and greater volume/frequency/consistency. But I don’t think it’s a settled answer!

Can we clarify, if we want to talk about VO2peak in any given workout (which we should be talking about instead of VO2max). Then we can probably say we don’t necessarily need to reach our HRmax to be at our highest achievable VO2peak on the day?

As in, practical training advice can account for not hitting strict 100% HRmax or VO2max in a “VO2max workout” (however we want to define that), for it to be appropriate and effective?

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I’m just talking about the physiology. What people choose to do with the information is a different question.

See my initial post:

So, while I don’t know what post or paper you are referencing, if the subjects continued for 15 minutes, that’s certainly a long enough period of time for significant cardiac drift to take place.

Pattern of HR as a function of exercise intensity in 22 international-caliber male cyclists. Regardless of whether they showed a heart rate deflection point (HDRP - i.e., Conconi point) or not, max HR and VO2max were achieved together.

My mid-day freakout is sponsored today by old_but_not_dead_yet. ;-D

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Not by a long shot.

Think about the components of the Fick equation:

VO2 = HR x SV x A-vO2diff

The latter increases rapidly with the transition from rest to low-to-moderate intensity exercise, but is already quite wide at even 50% of VO2max. After that, the only way for VO2 to still double (to 100% of VO2max) is for HR x SV - that is, cardiac output - to increase substantially.

It therefore follows mathematically that if your HR increases significantly once you’ve you’ve reached VO2max, then your SV must be decreasing to the same degree. During an incremental exercise test that only happens in clinical conditions, and not in healthy persons. (Note that we are not talking about changes in SV across intensities, or over longer periods of time, during which thermal stress can lead to significant cardiac drift.)

If HR continued to increase by 12 bpm during the last minute or so of a VO2max test in an ostensibly healthy athlete, I’d be looking very carefully at the data to make sure it isn’t a technical issue.

For example, you might see that pattern if the power output is incremented very rapidly, and the metabolic system is abnormally slow to respond (in which case VO2max has been underestimated). There are also systems out there that fail to accurately measure ventilation at high flow rates, again resulting in errors in VO2 and an apparent disconnect between VO2max and max HR.