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Jun 2017
11:53am, 7 Jun 2017
12 posts
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DMZ
Thanks for your thoughts Dvorak and J2R, very helpful! I guess VO2max sessions are just extremely difficult to do well, in the suggested HR range.
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Jun 2017
11:59am, 7 Jun 2017
482 posts
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AndrewS
MHR can vary a bit anyway. The excitability of conduction cells is dependent on several factors. So, you are only ever going to get an approximation unless you do your MHR test frequently.
The absolute upper limit of your HR is dictated by the time it takes for your conduction cells to depolarise and repolarise. Artificially (or pathologically) that maximum can be elevated to around 300 bpm. But, of course that is too fast for your ventricles to fill during diastole and you would die.
The MHR that you are looking for is the upper limit that you can produce, through exercise alone, that still allows for adequate diastolic filling.
If you do an exercise test to find your MHR and you are starting to feel unwell (vomit, get dizzy etc) then you are already heading past your max; your body is trying to put the brakes on your HR by activating your parasympathetic nervous system.
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Jun 2017
12:02pm, 7 Jun 2017
483 posts
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AndrewS
To clarify that last bit...the PNS is not causing the dizzyness, that is a sign of reduced cardiac output due to the drop in preload pressure (reduction in diastolic filling).
It will cause the nausea and vomitting though.
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Jun 2017
12:23pm, 7 Jun 2017
6,141 posts
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paul the builder
Andrew - that's a very interesting couple of posts. Thanks for that. Is that your line of work, or are you a keen amateur cardiac guy?
Brunski - 
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Jun 2017
12:30pm, 7 Jun 2017
269 posts
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SSLHP (Shoes smell like horse piss)
I think the bottom line is that your HRM in itself is unimportant. It just needs to be known so we can work out %s of it so we train appropriately. And the only really significant % is your Aerobic Threshold - 80% of your training should be below this and 20% above it.
If your MHR is 4 beats per minute inaccurate, then your Aerobic Threshold will only be 3 BPM inaccurate.
I've had to make some manual adjustments to the MHR I achieved in hill reps, partly because of what peeps are saying above but also my gut feeling and experience as to what my pace and perceived effort should be. I think I added about 6BPM to my recorded MHR.
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Jun 2017
12:43pm, 7 Jun 2017
484 posts
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AndrewS
SSLHP- Indeed. Unless you were doing all this in a lab with specialist equipment then you are only going to be dealing with approximations and that is good enough for everyone bar the elite afferleets.
Paul- yeah, something like that. Let's just say that I have 'some publications' in the field (not directly related to sports science though). I am not so involved these days but i still find it interesting.
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Jun 2017
12:55pm, 7 Jun 2017
11,171 posts
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Chrisull
So AndrewS - would it be safe to deduce as some studies of cyclists have seem to indicate, that maxHR can be altered by or during training macro cycles - and it isn't just a product of age/genetics ? And if not, where is the assumption flawed?
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Jun 2017
1:00pm, 7 Jun 2017
551 posts
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J2R
Chrisull, I recall Canute saying on here (or the Polarized Training thread) a while back that his maximum heart rate actually increases when he stops training for a while.
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Jun 2017
1:22pm, 7 Jun 2017
486 posts
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AndrewS
Chrisull- There is no doubt that age and genetics are the primary factors that determine this and many other variables related to conduction and haemodynamics. However, within these predisposing factors there will always be some variance.
This variance can be accounted for by slight changes in electrolyte concentrations or periods of training. Let's not forget that thyroid function is also a determinant for our metabolic rate...in fact, I could go on. The long and the short of it is that there are many, many factors that can lead to physical changes; there is no reason that maximum heart rate should be any different.
The problem with a lot of the sports science research that I have read is that they are based on the assumption that the human body acts and responds in a predictable way (like a machine). In reality, it would be almost impossible to control for all possible variables to draw any solid conclusion.
Once you understand what it is that makes the heart beat at the frequency that it does, then you would be unwise to state that MHR is fixed by genetics and age only.
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Jun 2017
2:29pm, 7 Jun 2017
13 posts
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DMZ
AndrewS, fascinating stuff, thanks!
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