# How accurate are heart rate monitors?



## gusmahler (Apr 7, 2012)

And how do I make it more accurate?

I just bought a Polar RS100 so I can track my training. First thing I did was put it on and lie down, to find my resting heart rate. I compared it to counting my pulse at my neck, and it was right on at 72. I got up to get a drink of water and the HRM shoots up to 90. I know I'm out of shape, but I can't be that out of shape, right? So I stopped, felt my heart rate at my neck and it is still around 72. I check the HRM and I see it drop to 72 immediately. 

So it seems that it senses any movement and interprets it as heart beat.

I took it on my bike this morning. It shoots up to the 120s and 130s within the first 5 minutes (where I'm taking it easy.) At the first stop light, I manually check my heart rate and it's 118. 

So I start pedaling faster and see rates above 155, which seems high, as I'm not exerting myself that hard. I stop pedaling and the heart rate immediately drops to the 130s. 

Is there anything I can do to make it more accurate? I followed the directions for placing the strap, but I'm wondering if there's a better position or something else I can do?


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## tlg (May 11, 2011)

Sounds pretty accurate to me. 
How are you manually checking your HR?


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## gusmahler (Apr 7, 2012)

tlg said:


> Sounds pretty accurate to me.
> How are you manually checking your HR?


Putting my finger on the artery in my neck, counting beats for 10 seconds, then multiplying by 6.

I guess I'm just surprised that it drops so quickly from 150 to 130 (or 90 to 70).


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## tlg (May 11, 2011)

gusmahler said:


> Putting my finger on the artery in my neck, counting beats for 10 seconds, then multiplying by 6.


That's not a very accurate way of checking your HR. If your count is off by 1-2, then when you multiply, your HR is off by 6-12. 
So your 118 manual HR could easily fall within (or over) the 120-130 from your HRM.
BTW, how did you get 118? 118/6=19.667


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## gusmahler (Apr 7, 2012)

tlg said:


> That's not a very accurate way of checking your HR. If your count is off by 1-2, then when you multiply, your HR is off by 6-12.
> So your 118 manual HR could easily fall within (or over) the 120-130 from your HRM.
> BTW, how did you get 118? 118/6=19.667


I meant to write 108.


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## drussell (Aug 6, 2010)

gusmahler said:


> And how do I make it more accurate?
> 
> I just bought a Polar CS100 so I can track my training. First thing I did was put it on and lie down, to find my resting heart rate. I compared it to counting my pulse at my neck, and it was right on at 72. I got up to get a drink of water and the HRM shoots up to 90. I know I'm out of shape, but I can't be that out of shape, right? So I stopped, felt my heart rate at my neck and it is still around 72. I check the HRM and I see it drop to 72 immediately.
> 
> ...


I did the same thing when I got mine at first. Everyone varies, but it sounds like you're probably within the error bars for going from a sitting to standing position.

As for your resting heart rate, it's properly taken first thing in the morning, even before sitting up in bed (see previous experiment going from sitting to standing). Try strapping the HRM on before you go to bed, and let it record overnight. The data is interesting to look at...

And those numbers on your bike seem pretty reasonable as well. You're first getting on the bike, so your body is getting warmed up, pumping more blood, getting more O2 in preparation for whatever is coming.

Also keep in mind that HR lags your activity. So if you're climbing a hill, it will be lower part way up the hill, and continue to be high for a short spell after you stop. This is why many serious athletes prefer training with a power meter - it's instantaneous.


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## PJ352 (Dec 5, 2007)

I agree with the others that your HRM is 'within tolerances' for accuracy. drussell makes a good point about what constitutes your resting HR.

Also, many trainers/ coaches consider recovery a better gauge of cardio fitness than resting or max HR, so you might want to read up on that topic. You should have gotten some relevant documentation with the unit.


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## Mufasa (Dec 12, 2011)

I've used the same monitor extensively. The HR has always been on the money. Yours sounds reasonable.


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## Akirasho (Jan 27, 2004)

... most HRMs, especially Polars, are medically certifiable with respect to accuracy... however, there may be a variety of sources for interference... most of which can be mitigated/eliminated (electrolytic gell/lotions may hold up better than sweat under some conditions)...


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## gusmahler (Apr 7, 2012)

Thanks everyone for your help, I now trust my monitor.

Here's what I don't understand. I was looking at CYCLING PERFORMANCE TIPS -

It describes zones based on my estimated max HR. I haven't tested my MHR, but using the formula 220-age, it should be 179.

That page describes 5 zones.

Zone 1 (recovery) up to 116 bpm
Zone 2 (Endurance) up to 129 bpm
Zone 3 (high level aerobic) up to 143
Zone 4 (lactate threshold) up to 161
Zone 5 (sprints) max HR. 

I only started cycling in April after being pretty sedentary for years, so I'm still out of shape. But the page says I should have, for example, an easy day in zone 2, up to 128. But my HR zooms past 128 just doing light warm-ups on my bike. By the end of my long, easy day today, I was pretty steady at 152, which is solidly in zone 4. It should have been difficult, but I wasn't tired and I easily could have carried on a conversation.


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## drussell (Aug 6, 2010)

That (220-age) formula is borderline useless (I'm 37 and my tested max HR is 196). There is more discussion about max HR here than you can shake a stick at, but essentially max hr is just that - the MAXIMUM rate at which your heart will beat, and you can only hold it for a few seconds at best. If you want a close approximation to it, find a decent hill (length and grade), and ride it as hard as you can. When you feel like you're about to die, keep going. Your field of vision will reduce to pinholes directly in front of you, your chest will feel like it's about to explode, your head will swim, etc. (Your HRM will need to record the data, because if you try to look at it on the computer, you'll probably fall over). The gist of doing it is that you are running yourself to the absolute limit. Now having said that, there's not much benefit in knowing your max HR as it is no indication of fitness, and not likely to change much. Consult your doctor before doing this if you are inclined, though, and have a friend handy to pick you up off the deck just in case.

Look up Lactate Threshold Heart Rate, and some of the tests for determining it (I use Friel's). This is a more reliable metric which will change with your fitness level, and is easier on your (biological) equipment.


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## drussell (Aug 6, 2010)

I just re-read your post and the first time missed you saying you're just starting and "still out of shape". I would strongly advise against the hill test. It really is a pretty unpleasant experience, and from my experience doing it, it took my 3 or 4 attempts (none on the same day) to see my peak at 196. That's a lot of punching yourself in the heart for a metric of questionable value.


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## gusmahler (Apr 7, 2012)

Thanks for the advice. There aren't any hills around me anyway, but I'll be sure not to do that test


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## nhluhr (Sep 9, 2010)

I can get my HR monitor to report 240 if I am not yet sweating and go down a steep hill. Once I start sweating, it settles down to accurate numbers. One thing I've found is that wetting my strap before I start riding gives me the realistic numbers sooner.


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