why can't HRM pick up from the wrist?
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krazyfranco posted 6 weeks ago.
Engineering question!
You can get your pulse in many place in the body - wrist, neck, behind the knee, groin, etc. by feeling for changes in pressure. However, HRM's don't detect pressure, they detect the electrical changes which cause a heartbeat. These electrical signals don't really exist in the other places you can get your pulse. These signals can be fairly easily detected by electrodes on the chest, especially because the heartbeat's electric signals are much greater in magnitude than other electrical signals in the area.
It would be sweet to have a HRM just be a wristwatch. It probably hasn't been done because the pressure changes on the wrist due to pulsating blood are very small compared to other pressure changes in the area from contracting muscles and such. Therefore, it would be hard to detect and distinguish your heartbeat from the pulse.
Anyway, thats my opinion, as a biomedical engineering student currently taking a class in sensors and measurements. Maybe I'll work on a pressure-sensitive HRM for my senior project?
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ChunkyB posted 6 weeks ago.
Here are a few that do just that. I think one issue might be accuracy/reliability, and if a chest strap is a ton more reliable and accurate, most people probably think you might as well just wear the strap. That reebok one actually has great reviews, so maybe there's something there.
http://www.nextag.com/strapless-heart-rate-monitor/search-html
http://www.heartratemonitor.co.uk/strapless_heart_rate_monitor.html
http://www.amazon.com/Reebok-Fitwatch-Strapless-Heart-Monitor/dp/B000G37H0M/ref=cm_cr_pr_pb_t/105-3322048-4818815
http://www.amazon.com/Reebok-Heart-Touch-Strapless-Monitor/dp/B000WUR358/ref=pd_bxgy_sg_img_b
"The melting point of wax means nothing to me": Thrice
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kylie posted 6 weeks ago.
Chunky -- those exist, but they only measure while you are touching with your finger. It is not a continuous reading.
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TryScott posted 6 weeks ago.
I can't believe I've gone this long without realizing that HRM's don't use pressure, they use electrical charges. Everything was there to figure it out, I just never made the connection. Why else would every HRM manual suggest you wet the contact area if it's not picking up your HR...
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Socket posted 6 weeks ago.
I had seen one that had a strap on your index finger that detected minute changes in translucency of the skin to determine pulse, but I can't find it now. I guess it would be an option, but I wouldn't be too keen on wearing a Nintendo PowerGlove while training :-)
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TriSooner posted 6 weeks ago.
krazyfranco wrote:
I dun learnt sometin' today.
HRM's don't detect pressure, they detect the electrical changes which cause a heartbeat.
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Leroy Bonkers posted 6 weeks ago.
krazyfranco wrote:
Engineering question!.......
Anyway, thats my opinion, as a biomedical engineering student currently taking a class in sensors and measurements.
I'm picturing Krazyfrano reading this post, getting wide eyes, sticking both hands in the air and yelling "yes! this is the one I've been waiting for!" - - awesome to have a budding expert on board.
I wish that HRM came in just the watch portion without the need for that bra strap transmitter.
I wonder why the pickup sensors can't be built into the wrist strap to pick up the pulse from there...