Heart rate
302 watchers
Oct 2018
6:06pm, 13 Oct 2018
1,895 posts
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Canute
Although atrial fibrillation (AF) is a relatively common rhythm disturbance in elderly runners (especially in males) it is not directly fatal. Indeed it is difficult to establish whether or not AF associated with any increased in mortality in athletes. Ventricular fibrillation (VF) on the other hand is often fatal. In young athletes, VF is likely to due to congenital abnormalities such as hypertrophic cardiomyopathy. In the elderly VF is probably due to degenerative disease, including atherosclerosis. This raises the question of whether the relevant degenerative change might be detected early. Atherosclerosis might produce angina etc. It might also be associated with high blood pressure which is detectable. But in asymptomatic elderly runners, it is not clear what we can look out for. Although the evidence is tenuous, I suspect that increasing frequency of ventricular ectopic beats (VEBs), especially during cool down, might be a significant indicator of increasing risk. VEBs are beats that arise when the cardiac contraction is initiated by premature firing of over-excitable muscle cells in the ventricular wall. Sometimes you feel an apparent missed beat, because the premature contraction occurs before the ventricle is full and produces only a weak pulsation. Many people have occasional VEBs. 24 hour monitoring reveals at least one VEB in 24 hours in about half of the population. In some people VEBs can be much more common (e.g. more than 1 per minute). Frequent VEB’s are often benign but there is an association between frequent VEBs and subsequent sudden cardiac death. In particular, frequent VEB’s during and immediately after exercise are more sinister. You can detect VEBs fairly reliably with a HRM that records R-R intervals. They often appear as missed R waves, and are sometimes followed immediately by a compensatory acceleration of heart rate. I do not know of any good studies that have demonstrated that recording R-R intervals regularly during training is an effective way of identifying an increasing risk of sudden cardiac death, but it seems to me that in an elderly runner with additional possible risk factors such as ventricular hypertrophy, it might be worthwhile. I have clear evidence of left ventricular hypertrophy. I also have a strong family history of high blood pressure (and stroke). My own blood pressure tends towards the worrying level, but I do not consider it is worth taking antihypertensive medication. I believe exercise and heathy diet are the best way to keep it under control. A few years ago, when in my late 60’s and doing fairly intense training, I decided that on account of my various cardiac risk factors, it was worth monitoring R-R intervals during exercise and during the cool down. I noted VEBs from time to time (typically several per hour while running), but the frequency of these showed no sign of increasing so I continued to train intensely. However if the frequency of VEBs had shown signs of substantial increase, I was prepared to cut back exercise intensity. In fact the frequency of VEBs showed no sign of increasing in the five years from 65 to 70. Since I turned 70 I have not trained intensely nor raced seriously, because at the moment there are plenty of other things I enjoy that keep me busy. Therefore I no longer use a HRM. I do occasionally note a few missed beats (detectable by palpation of my pulse at the wrist) during cool down but I do not consider this is cause for worry. However if at any time in the future I decide to train intensely again, I will once again use a HRM with R-R capability. |
Oct 2018
2:25pm, 14 Oct 2018
13,352 posts
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Chrisull
Canute - as always, valuable and informative input. How do you know if your HRM measures R-R capability? I assume standard ones don't?
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Oct 2018
10:54pm, 14 Oct 2018
1,422 posts
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J2R
I ran my fastest ever half marathon in early March, with an average heart rate of 165bpm. Today I got almost exactly the same time, but with an average heart rate of 158bpm. Given that the temperature both days was similar, and both were fast, flat courses, I'm inclined to see this as an improvement (although of course, I actually want to improve my time, not the heart rate I run it at). But does this actually tell me anything useful?
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Oct 2018
11:05pm, 14 Oct 2018
9,904 posts
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Badger
Chris, the standard ANT+ HRMs detect the R-R intervals; Garmins don't record them unless you've switched that facility on, generally for using Firstbeat software. I think Suuntos do by default. Canute, what were you using, and how were you getting at the values? J, arguably right now it's saying you've trained yourself to sustain that specific pace for longer, but not to go faster as yet? Which is an improvement. |
Oct 2018
12:40am, 15 Oct 2018
1,077 posts
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A65
I assume that all chest strap HRM's use R-R interval to measure HR. The R wave represents the largest amount of electrical energy and (should) correspond to Ventricular contraction. Optical HRM's are essential doing the same thing. |
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Oct 2018
12:42am, 15 Oct 2018
1,078 posts
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A65
...unless you mean the way that HR is calculated? I.e. 60/R-R= HR as opposed to the HRM counting the R waves over a minute. |
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Oct 2018
2:02pm, 15 Oct 2018
1,896 posts
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Canute
The R wave is a very sharp spike in the ECG record. It is only about 30-40 milliseconds wide and typically rises to a height of over 1 millivolt. The other characteristic waves of the ECG (eg P wave and T wave) are broader and much lower in amplitude. The R wave in produced by the wave of electrical depolarization that sweeps across the ventricles and produces the contraction that ejects a pulse of blood from the heart into the arteries. In a HRM chest strap, the sensor detects the sharp R wave because it is so much sharper than the other waves. The computer in the watch counts the number of R waves per second. All chest strap HRM detect R waves, but not all of them save the time of occurrence of every individual R wave, as this uses a lot of storage capacity. However some HRMs are do have the capacity to store and subsequently output the time of each individual R wave, though you have to specifically set R-R as an option before the recording begins. Several Suunto and Polar models have this facility. I use a Polar rs800cx. The rs800cx is an old model that was developed in the era when people were very enthusiastic about measuring Heart Rate Variability (HRV) as an indicator of over-training. HRV is variation in the time interval between consecutive R waves (the R-R interval). However, since the rise of popular enthusiasm for GPS facilities, Polar more effort into design of GPS facilities than in updating their R-R technology. Nonetheless, the Rs800Cx is pretty reliable – the main problem, as with all chest strap HRM’s, is maintaining good contact with the skin and avoiding static. Optical HRMs record the pulsation of blood in the small arterioles beneath the skin of the wrist. There is generally a one to one correspondence between R waves and blood pulsations, but the pressure pulsations are not as sharp as the R wave. In principle, it would be possible to produce a time course of the pressure pulsations but the timing would be less precise than the R-R record because the pulsation is broader in time. The estimate of HRV would be less accurate. As far as I know, no manufacturer of Optical HRMs has provided the ability to save and output the timing of each pressure pulsation. If I start intense training again I will use my rs800cx. I am afraid I cannot give an up-to date critique of the best devices with R-R capability. |
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Oct 2018
2:14pm, 15 Oct 2018
1,426 posts
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J2R
It may be stating the obvious, but you can certainly get more information about R-R intervals with a smartphone app than with a standard GPS watch. It's used in HRV apps like EliteHRV.
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Oct 2018
2:24pm, 15 Oct 2018
29,366 posts
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HappyG(rrr)
Heart Rate Variability would be really useful to track, for both health and fitness, and yet I've never seen e.g. Garmin, do any analysis or output for it (even if the raw data did hold it). Isn't it the case that HRV can be an indicator of heart fitness, and most importantly, of possible heart problems. If all HRMs have the ability to record it, is there any reason why it's not something that is regularly output in the apps?  G
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Oct 2018
3:13pm, 15 Oct 2018
6,348 posts
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The_Saint
I was told by a PhD student when I was taking part in his study sandomenico.uk that the whole area of HRV is fascinating but nobody can really say what it means or use it for anything other than to say in a hand-wavy way that more is better. |
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