Weird Heart Rate Data (a.k.a Is There A Doctor In The House?

[Norm]

I have some weird heart rate data and am wondering if anyone else has seen similar data streams.

About every 10 minutes I get a substantial dip in my heart rate. I've also seen spikes spaced about 10 minutes apart.

The attached image is an example from an indoor ride last night. In it you'll see 5 pronounced dips and 2 pronounced spikes. There doesn't seem to be anything in the power or cadence data that would indicate a change in physical exertion. Further, the regular frequency of events looks suspicious to me.

Now that I've noticed this pattern, I've found it in all my recent indoor rides. It's a bit harder to find it in outdoor rides because the data isn't as smooth, but I think I see it there as well. (I'll have to do more research into the outdoor rides.)

Any thoughts?

Picture 4.png (46.09 KiB) Viewed 15220 times

[Velocomp]

It's very possible that your issue is that your jersey is creating static electricity that causes the weird spikes. This is characteristic of HR straps.

Make sure your strap is tight and that your jersey flops around as little as possible.

[Norm]

Thanks John. I had forgotten about that.

This ride was indoors, so I wasn't wearing a jersey -- just bibs.

The regularity of the events is suspicious to me. Travis suggested that they might be caused by WiFi, cell phone, or some other device that creates a regular burst of RF.

[Velocomp]

Travis is a very smart guy.

It is indeed the case that strong EMI can screw up the (pretty small) signals from the wireless sensors. Boyd Johnson rides past TV towers and microwave towers on one of his training rides and it fouls up his wireless communications every time!

[Norm]

Round 2: I traveled south a couple of hundred miles with my rollers this week. In a completely different environment, I found the same regular heart rate dips as illustrated at the top of this thread. Since I wouldn't expect the same kind of EMI in a different location, I suppose I should look for a different cause.

Has anyone else out there seen similar runs of regular heart rate dips? My dips are 'V' shaped, about 10 bpm deep, occur every 7 to 11 minutes, last about 20 to 30 seconds from shoulder to shoulder, and seem to be unrelated to physical exertion.

Could this be a real heart rate pattern? As you might guess, I'd prefer an equipment-oriented explanation. Kudos to anyone who can suggest one.

[travispape]

I've never tried wear more than one strap at a time, but it might be interesting to put on a Polar or something else that operates with a different wireless protocol. (Suunto?) I don't know if they would interfere. Anyway, if both dip then that would be an indication that the phenomenon is real.

[Norm]

I'd have to wear something that could capture the data: I've never seen the dip while on the bike -- I only see it in the ride file.

[racerfern]

Has anyone else out there seen similar runs of regular heart rate dips? My dips are 'V' shaped, about 10 bpm deep, occur every 7 to 11 minutes, last about 20 to 30 seconds from shoulder to shoulder, and seem to be unrelated to physical exertion.

Could this be a real heart rate pattern? As you might guess, I'd prefer an equipment-oriented explanation. Kudos to anyone who can suggest one.

I'm not sure I agree with your statement that they seem to be unrelated to physical exertion. Almost all the dips are associated with drops in power, although not all of them are as significant or clear cut as others. Although your perceived exertion may be intense, your actual physical output may suddenly drop until you realize and "push on the gas" again.

This doesn't explain all the irregularities away but I think you need to zoom in and take a closer look at the data and at your habits on the roller. Are you leaning over to adjust something, your iPod, whatever and changing the contact the HR strap makes with your body? Anything?

[Norm]

My first thought was to blame the dips on bad contact between my chest and strap, so I thought I'd try some chest strap gel. That experiment is still waiting for me to find some gel.

Then I looked at the frequency of the dips. They seem to occur with unusual regularity. I wouldn't expect position adjustments, reaching for towel or water, etc. to occur with such a regular frequency.

Then I looked at the depth of the dips. For me, a 10 bpm drop in heartrate is usually a prolonged affair: For example, after a 20 minute FT interval I drop my power by 100 watts to rest. It takes 10 seconds for heart rate to begin to react and then it declines at a gentle 0.5 bpm per second. In the dips at the top of this post, there's nowhere near a 100 watt dip in power, yet heart rate falls at a rate of about 1 bpm per second for about 10 or 12 seconds before it recovers.

All that being said, you may be right: This might be my real heart rate responding to variations in effort. It's just weird to see heart rate staying in such a narrow band except for these rapid dip and recoveries.

[racerfern]

I use a gel from http://www.uni-patch.com . It's available at medical supply stores that sells wheelchairs, etc. I figure after a couple more years of riding I'll be ready for at least a walker so I'm trying to get friendly with the owner. Those things aren't cheap.

[cujo]

The cause may be your rollers. I have a couple sets of rollers. They both produce static. You could be building a small charge every 10 minutes or so. I could be so small you do not notice the discharge as a shock. Your equipment is much more intune to these changes. Try changing trainers for a ride and see if it continues.

I will also say though that the more fit you are the more Jagged the information might look. If you look at elite rider vo2 test and compare them to club riders, the club riders look very smooth upward slope, The elite riders tend to raise and dip alot more though maintianing a steady upward trend. I hope that made since.

Joey Coddington
DLP Racing

[Norm]

That explanation makes a lot of sense! Friction between the wheels and the rollers generate a static charge -- of course!

But if the charge to too small to feel the discharge, how in the world did you figure out that you generate static electricity while on the rollers?

I'll switch to a trainer for a ride or two to see what happens. Thanks!

[cujo]

I noticed larger charges. I also notices some small pet hair on my roller standing on end. Then other times nothing. You may try a humidifer od de-humidifer mostiure in the air effects static charge.

Joey
DLP Racing

[Norm]

Yeah, the rollers are definitely generating some static electricity. While I was on the rollers a couple of nights ago I reached over and touched my girlfriend and got a pretty good spark. I have wood floors and don't normally have static electricity.

[racerfern]

You're not the only one. Assuming the following link is also an indoor ride based on the HR consistency, the roller static electricity theory makes more and more sense.

http://www.zonefivesoftware.com/SportTr ... highlight=

Have you solved it? Grounding the rollers? Grounding the bike to the roller mechanism?

[lorduintah]

I started getting very wide ranging HR values on a ride yesterday.

It was the first time I had worn a combination of an under-layer and jersey. I could get the HR back to normal if I rubbed the contacts a little and moved them around on my skin.

This could have been charge build up, but that shows up as a spike not a delta of 20 or more BPM and remains steady.

So when I got home:

1 - Cleaned the strap of all the gunk that had built up with an old toothbrush.
2 - Replaced the battery.
3 - Went back to my normal under-layer - not cotton and silk combination as before.

Steady HR as a result of these or a combination. I would suggest one at a time kind of experiment, but it was probably the clean up that was a major contributor.

Tom


PS --- If all else fails, remove the battery on the HR detector, reverse the sides (flip it over) and put it back into the receptacle for a moment - the resets the detector and also changes the ID. Flip the battery back over and screw the cap back on.

[gregh3285]

I'm not entirely sure that I buy the ESD explanation. I've seen a lot of weird heart rate data at the beginning of rides. However, as soon as I build up a sweat and get my chest strap and base layer damp, the data tends to straighten out. I do find that wearing a base layer contributes to issues. Even if you did have an ESD burst that interrupted telemetry, is it going to confuse things for a full 20 to 30 seconds? I'd change batteries. Also when you start your ride use water to dampen your base layer and your strap. In the bigger picture this sort of stuff isn't a huge deal. But isn't just annoying? It's like a mosquito bit. Good luck.

[lorduintah]

I was not really focusing on ESD - that should only be a spike.

The battery - yes that could easily be at issue. I did also get rid of the remnants of this freaky drift by doing the reset of the unit with the battery flip.

Tom


It can be in appearance huge when you see BPM > 200!

[Norm]

You're not the only one. Assuming the following link is also an indoor ride based on the HR consistency, the roller static electricity theory makes more and more sense.

http://www.zonefivesoftware.com/SportTr ... highlight=

Have you solved it? Grounding the rollers? Grounding the bike to the roller mechanism?

Thanks for the pointer. No, I haven't solved it. I've tried new batteries, cleaning the strap, extra moistness on my chest, and tightening the strap. Nothing seems to make a difference. And I've found that it's not limited to roller rides either: Outdoor rides are showing the same kinds of dips.

I'll have a CycleOps chest strap to test in a week or so. I'll be sure to let the board know if it shows an improvement.

[nreimche]

I like how you used the word 'WEIRD', instead of 'CRAZY'! Some people act, speak, or do as if everything extreme or inefficient (Example: your dips in HR), as long as the word crazy is used, that all mentally ill people (I.E. those w/ schizophrenia, bipolar disorder, etc.) must do those things that are extreme or inefficient, or should I say inSUFFICIENT? Part of the illness lies in the acceptence of one's peers (i.e. If you choose not, or can't, EMPATHIZE or wair shoes then expect someone, even you, to hurt!). I choose gentleness, even, if you think YOU can put words into my head. I am using an IBIKE W/ SCHIZOPHRENIA, what do you think? IMPOSSIBLE? NEVER!

P.S. Some people have schizophrenia so exaggerated, they think I have no hobbies, or kindness...amongst other things!

[Norm]

OK, the data is in and the answer for me was... [drumroll please...] a bad heart strap!

I recently acquired a Cycleops heart strap, paired it with my gen iii iAero, and, presto, no more heart rate dips! So it appears that my iBike strap has some sort of malfunction that causes the weird data I've been seeing.

Thanks for all the help and speculation.