What! A heart rate of 280bpm, that can’t be right can it? Oh hang on a minute now there’s no reading at all.
Most of you have been there with Garmin HR straps. It’s annoying when the readings are wrong especially if you train by heart rate. Luckily you’ve just bought an expensive, optical HR device for your wrist – or maybe even for your upper arm or ear. Let’s say ‘wrist’ for now. Surely new technology can only make accuracy better?
Nope. More than likely the optical situation will make matters worse for the general population and their optical HR woes.
Anyway DC inspired me to update an old post of mine with lots of lovely 2017-opticalness.
OPTICAL HEART RATE ISSUES – FIXING
I thought I knew what I was doing with chest straps. I didn’t have many problems that weren’t easily solved by buying a new one. Conversely I might wear one optical heart rate device with no problems for a while and then a new model arrives and I wear it in EXACTLY the same place and do the EXACT-SAME sporting things…but the HR readings are rubbish.
There is a lot going on here and I’m not convinced that anyone quite understands why sometimes things just don’t work with optical HR.
You’ve probably read about these:
- oHR can sometimes be tricky on darker skin
- oHR can sometimes be tricky on hairy skin
- oHR can sometimes be tricky if you have a higher fat content on your lower arms
- oHR is affected by blood circulation (it takes the reading from bouncing light off blood…so there must be blood)
So the solutions are simple: lose weight; don’t get a tan/change ethnicity; cure Raynaud’s syndrome; and shave your lower arm hairs! Not very helpful, sorry.
The quality of the sensor is important and these are some of the factors that go into making a good piece of hardware:
- Colour(s) of the LEDs
- Spacing of the LEDs
- Shielding the shone and received light from interference of other light sources of similar wavelengths
But, perhaps even more than that, the watch/sensor manufacturer will most likely have to add a mathematical algorithm (software) to deal with: the swinging of your arm; the flexing of your wrist; and the particular bounce-type of whichever sport you are doing. Yes the algorithm will probably vary from sport to sport.
1st TIP: Use the right sport profile or just stick to the sport profile where it seems to work best
You will no doubt have read the user manual that came with your errant watch. It will likely say something like “wear the watch 1cm from the wrist bone and wear the strap tight but not too tight to leave mark”.
2nd TIP: Wear it tightly 😉 and If practical wear it further from the wrist.
But I’ve found that even when wearing it in the ‘right place’ (1cm from your wrist) that the blooming thing can slip down back to the wrist. Yet, as alluded to earlier, with some devices this causes no problems but with others it does.
3rd TIP: Try the other arm to find a bit more watch-strap friction
In some of my more ridiculous moments I have pounded the streets of SW London wearing several watches. This is not a good idea. As well as the watches banging into each other and ruining the optical HR signal I have heard that it is possible for one optical LED from watch to affect the sensor on another watch and they do not even have to be next to each other/ maybe the light goes within the body or directly through the air. Someone with a grasp of physics can clarify that one for me.
4th TIP (just for me) only wear one optical HR device per arm or even just one in total.
So with all this ‘pounding’ going on, what personal factors could make that pounding worse? Maybe if you have a heavy impact when you run that could be a factor but maybe even the weight of the watch could be a factor as a heavier watch could move about more than a lighter one? This might explain some of my recent Garmin Fenix 5X woes – beautiful watch but heavy and I’ve not found the oHR as good as other, earlier Garmins like the 735XT.
5th TIP: Run lightly and avoid bumps in the road
More recently I’ve seen some issues with optical HR devices seeming to take 15 to 30 minutes to ‘warm up’. Maybe it’s me warming up 😉 and getting the blood flowing.
6th TIP: Cover every angle of warming up – from a proper physical warmup to wearing the device before your exercise to ‘get it warmer’ and maybe even try recording a pre-run 15 minute dummy session.
That’s probably covered most avenues. If you have any other suggestions MANY other people will gratefully receive them. Thank you
7th TIP: Buy a chest strap 😉
CHEST STRAP HEART RATE ISSUES – FIXING
But on that note there are problems with chest straps too. I generally don’t have any problems with straps less than a year old. For some of the older Polar/Suunto/Garmin straps it was often either the STRAP (not the pod) or the BATTERY that was the cause of the problem rather than the physical ‘HR ‘pod’.
Firstly there could be a fault with your STRAP and/or your heart rate SENSOR / POD. I think that is unlikely in most cases where you have relatively new equipment.
Secondly if you have ever used a Garmin HARD strap you will probably have never found any problems. So that shows that the problem probably does not lie with the watch. If, like me, you may have bought a POLAR soft strap to which the GARMIN POD fits you will probably found the same level of HR spikes and dropouts in similar circumstances. Therefore this suggests to me that there is nothing inherently uniquely wrong with Garmin’s design.
It’s just that soft straps for some reason are more prone to the sort of behaviour we are talking about. Why? If you look at the reverse of the strap you will see that the smooth ‘rubber’ contact area may be smaller on a soft strap.
This post is an updated version of (this) post from 2013:
Yesterday I had a turbo session indoors. Nothing too hard but a bit sweaty nevertheless. Immediately afterwards I went for a slow run in the freezing cold. Within 5 minutes I had incorrect HR readings. I had stopped sweating and some of the sweat already there had dried out. This to me VERY strongly suggests that the problem is related to the contact between the body/chest and the strap.
In really cold or really dry weather you may well find you are more prone to spikes. This could be because both hot and cold weather can have less humidity (humidity might be a factor). Or it could also be the case that when really cold you might not sweat much or when really hot and you are not trying much the sweat very quickly evaporates.
Similarly in early Spring or late Autumn/Fall when I am wearing thin clothing and cycling quickly I find some instances where I lose a HR signal and attribute this to the air movement causing all the sweat to evaporate and dry my skin.
Either way a wet strap helps.
So if you lick your strap before any exercise you will probably find an improvement.
8th TIP: Lick it!
Furthermore if you thoroughly wet the strap, you may find yet more improvement.
Garmin recommend that you use medical grade gel. I bought some and found that saliva was just as effective BUT saliva would more readily dry out in certain conditions.
Well 30 minutes after posting the original article I got this from Cy Gearing on FB:
Cy Gearing :: I use the garmin soft strap and use a gel from amazon. I don’t sweat a great deal so had issues, but been using the gel for 3 months now without dropouts. It cost the vast sum of £3.05 for 2 x100ml bottles and you need so little that I’m sure they will last at least a year!
So this I think backs up my assertion that it is a contact problem rather than static or faulty devices. Although Cy has obviously found that gel makes a significant improvement (well if 100% counts as significant!).
UNUSUAL (9th) TIP: Take out the battery and put it in the wrong way. Then put it in the right way.
However static might be a cause. BUT two different materials are required for static to happen (physics). This could be different shorts and shirt. Or it could be the soft strap and your shirt rubbing together. It might also be linked to static from body hair. I’m not convinced about this explanation but it is possible. I still have problems when ‘topless’ on my turbo. Static absolutely CANNOT be the cause in that scenario. Although it might be a contributory factor in other scenarios.
Finally you need to wear it in the right place! The centre of the pod goes over your solar plexus just below your rib cage. This is easier said than done for some people who find it extremely hard to get the chest strap to stay in the right place and, in fact, one of the reasons why lots of people buy the optical HR devices we started talking about at the top of the post!.
10th TIP: Wear it in the right place or buy an optical HRM…oh dear 🙂
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