Vo2max, MHR too high, MHR too low?

Part of the estimate for your VO2 will be the "headroom" between your HR for any given activity and the maximum you could (supposedly) have achieved. Thus the higher your MHR, the more headroom and thus the tendency of the algorithm to return a higher VO2. Conversely, the lower your entered MHR, the lower your VO2. I don't know how complicated the calculation is or what weighting is given to MHR in it - clearly people with very different MHRs can have equally high or low VO2 estimates - but I believe the above is directionally correct.

Ok thanks, make sense.

Also how I thought I would play out.
So if you have too high MHR set, the vo2max is probably going to be higher than “real vo2max”

Exactly. I saw a big and permanent drop in my VO2 when I did an MHR test and discovered my real MHR was far lower than I had been blithely putting into Connect for many years. 

Interesting!
I believe my MHR might be a little high as well, I did got 207bpm during last stages of a 10k race about 1,5 years ago. I have set 205 as MHR now. If I don’t reach at least 200ish during a really maximum effort later this spring I’ll lower MHR as well.

Wow! That's high! I might be on the low end for MHR. The highest I've ever achieved from hard sprints was in the low 180s. At tempo run pace, my HR is about 170. My resting heart rate is in the mid 30s. 

Yes it’s high. And I’m a little over 40years old as well. I don’t know why I’ve always have had high MHR. My RHR is 49-52 ish.

But as I said, I wonder if I’m still at 205, I will know in a while when I manage to do a good MHR run.

But I can hold ~185 for good period of time during training, so I guess my MHR is still around 200.

The human body is a strange thing 

I agree with davidhurst - an artificially high MHR will lead to an overestimate of VO2Max.

Say you are running at 140 bpm at a given pace. If you enter 200 for your MHR, it will think you are cruising along pretty efficiently at 70% of maxHR, and therefore at maximum effort you could go a lot faster. If your true MHR was 180, you would be doing 78% of MHR for that pace, so while you could go a bit faster at maximum effort, not that much faster.

The age-based prediction of MHR is based on the average of the population - but like most averages, is made up of a wide range of individual MHRs distributed about a mean. The standard deviation of the age-based prediction is 13 bpm, or put another way, around 1/3 of the population has MHR more than 13 bpm away from the age-based prediction.

Food for thought, I had done a self tested max like 10yrs ago on treadmill incline sprints... was hellish (usually could muster 192-194).  Back then I could get my HR up into the 190s much easier than now (training way more after taking up running marathons, ultras, and biking 100+miles) now I am lucky if I can hit 185 in hard sprints.  Kind of figured my maximum heart rate had dropped from my 28-30s to just now being 38-40.... however 2yrs ago I ran a warm July 5km race (PR) and pushed a finish sprint the last minute that made my eyes blurry!  Heart rate slowly rose to 195 in that last minute! (using HR chest strap)!  After the race I was shocked to see that my maximum HR hadn't changed from what I thought it was!   I just hadn't had the opportunity to push it up (adreneline, heat, race conditions, fresh legs, etc)

So if you saw 207 (assuming heart rate curve looks 'real' / good... ) there is no reason it wouldn't be 207 (if not higher!), I am not sure that 10km is really the best situation for a super high HR as it is starting to be quite an endurance distance for most people (unless you are under maybe 38-37min?) unless you held a decent bit back to get a long sprint on.

Max HR is supposed to drop about a bpm per year after the age of 40, so the poster's example of a test yielding 207 a few years ago and his using 205 now should be in the right ball park.

Hi Nickmn

interesting!
yes I do have considered this carefully, I know vo2max will differ a lot and my zones wouldn’t really fit if I didn’t get it reasonably right.

And your story kind of confirm my thoughts a bit.

And sure 10km shouldn’t be optimal for a MHR test, but apparently that did the trick (race day and so on) I’ve been in the 202-205 during tough training sessions as well.

So yea, probably I’m just about correct about my assessment of MHR now.

and reason for not testing MHR  again now recently is that I’m in a kind of a run streak, and will keep going for a while I think, so I’m not really extra fresh in my legs most of the time

about the distance btw, I am use to the distance, and only ran 10km or more last two years, but my PR is modest 46min.

this year though, I’m increasing distance a lot, and adding loads of slow  and or shorter runs as well. So let’s se what happens now :)

Thanks for your answer!