RHYTHM+ Heart Rate Monitor

Anyone who uses a Garmin heart rate strap knows that the chest style is tried tested and true but sometimes they do just crap out. Whenever you buy a Garmin device there is usually an option to get the device itself or in a bundle with a HR strap. I have always just got the device because of already owning an existing strap. When my last strap started to give me drop outs and reedings that were way off I knew something was up.  I have in the past always used a little dab of ultrasound gel on my Garmin chest strap and fresh batteries to insure that I would get the best reading possible but despite these efforts my strap had failed.  I believe it to be a result of moisture getting into the contacts of the strap because they were rusty from sweating like a horse.

I looked around at new fan-dangled alternatives and decided that optical might be the way to go. The Scosche Rhythm+ had a soft strap unlike the MIOs that were another watch band style so I decided to give the Rhythm+ a go mainly because of the comfort strap and that I could drop in my local MEC and pick it up.

When I say optical for those of you that are not familiar with this technology it has been around a long time. Hospitals use a variation of an optical sensor known as pulse oximetry which measures oxygen in the blood at your fingertip. The concept is the same when it comes to the Rhythm and the MIO both use whats called reflection pulse oximetry, which is just a different placement of the LEDS and receptors. If you are an apple fan and own a new “apple watch” then you already know it has pulse oximeter in the back with some LEDs that is how it reads your HR.

21072175070_5e0323ef29_z“A typical pulse oximeter utilizes an electronic processor and a pair of small light-emitting diodes (LEDs) facing a photodiode through a translucent part of the patient’s body, usually a fingertip or an earlobe.”

“What this means is at the measuring site there are constant light absorbers that are always present. They are skin, tissue, venous blood, and the arterial blood. However, with each heart beat the heart contracts and there is a surge of arterial blood, which momentarily increases arterial blood volume across the measuring site. This results in more light absorption during the surge. If light signals received at the photodetector are looked at as a waveform, there should be peaks with each heartbeat and troughs between heartbeats. If the light absorption at the trough is subtracted from the light absorption at the peak then, in theory, the results are the absorption characteristics due to added volume of blood only; which is arterial. Since peaks occur with each heartbeat or pulse, the term “pulse oximetry” was coined. “

In the case of the Rhythm+ it utilizes three LEDs two green and one yellow to send pulses of light against your skin which is then measured by the photodetector and after it crunches some fancy data your pulse is displayed. While there is a lot more scientific description like above that is easiest to understand.

The Rhythm+ is charged via a USB cradle not unlike many other Garmin devices and lasts me about 7hrs on a full charge (just shy of the claimed 8hrs). With it’s dual-mode processor you can simultaneously transmit your heart rate to multiple ANT+ displays and Bluetooth Smart enabled watches and smartphones.  This gives you all the flexibility you need when it comes to a single heart rate monitor that works with the oldest Garmin to the newest smartphones. All you triathlon fans will be happy to know it is IP67 Waterproof construction and can be submerged up to 1 meter.  Comfort is key when racing and training so the fact that it has a breathable lightweight armband and not a clunky wrist watch clasp was a selling point for me. I forget it is even on my forearm or wrist. When it comes to placement of the Rhythm+ I have found I can wear it on my ankle, wrist and forearm all with steady readings and no problems. Pretty much where you can strap this thing it will read your pulse even pushed against your face it will read. 21249772522_e270f046f5_z

I was worried that I would bump the on / off button under the rubber protective top but you have to press and hold the button for a few seconds no matter if you are turning it on or off so this hasn’t been a issue at all. Even traveling I would throw it in my bag and not worry it was going to turn itself on.

 

You can see what looks like a purple LED in the pic below and that is how it looks when connected to both Bluetooth and ANT+. There is a red led to indicate low battery and charging status as well as a blue one for Bluetooth indication. This LED blinks constantly while the device is on and when off you see no lights at all.

This has been working for me for the past few months flawlessly and I have never had any pairing issues connecting and disconnecting from all kinds of devices. If your chest strap ever bites the dust or you just want something to get for Christmas …. yes its coming….. put this little guy on your list you will be happy you did.

 

For a super in depth review check out DC Rainmaker’s Blog where he gets into the nitty gritty / super scientific testing and stuff.

Thanks for reading.

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