Review of the Scosche RYTHM+ Heart Rate Monitor

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If you have a GPS watch, you’re very likely to have the chest strap holding the device used for measuring your heart rate. The strap has to be tightly secured on your chest in order to capture a good HR signal. It sends to your GPS watch via Ant+ or Bluetooth LE to a phone or a Bluetooth LE watch. There’s been a lot of sport watches recently removing the need for a HR chest strap as they measure the heart rate using an optical sensor at the wrist level. The famous watches doing this are: Myo, Apple Watch, … The issue is that if you don’t want to change watch or use your phone, you have no other choice than a chest strap… until the RYTHM+.

Getting a unit and opening the box

I learned about this heart rate monitor through my friend Karsten Korbel. He was also tired of the chest strap, which always ends up either constricting you or chaffing badly at various place (the front unit and on the lock between the two parts of the strap). He was also doing other exercises at the gym where wearing a chest strap is simply unpractical or impossible. As such he looked for alternatives, found the Scosche product, bought it from the US. Over a chat he mentioned it and I told myself “oh, it would be nice to get one, maybe I should try it before ordering from the US…”. I was in Sydney, Australia for a business trip and checked if it was sold there. Yes ! It was sold in one of the biggest electronic consumer chain (JB-Hifi) and it was even on sale ! I bought one for 98 AUD (normal price 129 AUD). The retail price in the US is 79.99 USD. At today’s current Ringitt exchange rate, I bought it for 298RM, whites about 70 USD. Quite a bargain in fact ! They also sell replacement bands with different colors.

When you open the box, you have the following items:

  1. The heart rate monitor device with one “long” strap
  2. A shorter strap
  3. The USB cradle for charging the Rhythm+
  4. The user’s guide (2 pages in fact for each language)

Charging the Rythm+

You have to use the USB cradle. It hooks into the Rythm+ and can’t be removed by mistake. That’s good. It took about X hours to recharge it fully.

The features of the Rhythm+

It’s basically an optical heart rate monitor which provides Ant+ and Bluetooth LE connectivity. It’s using an optical sensor from Valencell. The other option in the market is Mio. I don’t know the difference in term of accuracy but the folks I know with Mio (either from Mio or OEMed by another vendor, for example Garmin Forerunner 225) are happy with it. One cool thing is that you can pair it with multiple devices: a GPS watch using Ant+, a Phone using Bluetooth. It can even send data concurrently to both.

The sensor does work with various skin color. They say they use different type of LED (green and orange) so that they can adapt to all type of skins. It is charged via USB using a cradle (common for GPS watches) and the battery is said to last 8 hours. I still need to try to do accurate measurements here. It won’t last for a long ultra for sure… but it’s better than no strap. They say it works up to 100 feet (with nothing in between). For a runner it does not mean much but if you are at the gym, you can leave your phone in one corner and carry on with your activities while still recording data. That’s nice. My bluetooth speakers are much worse than that… By the way, it’s IP67 resistant, which means it will be OK with sweat and can be put in 1 meter of water for 30n. If you go running  and it rains, it should be OK.

Pairing the Rythm+ with your phone or watch

It’s very easy… Put the device in pairing mode, switch it on then look for it with your device. That’s as simple as that. On my Garmin Fenix 3, it is registered as a HR sensor. I have the traditional chest strap and the Rythm+. Only one can be used at once of course… On the phone, I use Endomondo and it’s very easy too. You say you want to add a HR belt, it’s asking you Ant+ or Bluetooth. I chose Bluetooth then the phone found it straight away and asked me if I wanted to pair with it. After that, I can use the Rythm+ immediately 🙂

Position of the sensor

The sensor has to be positioned with the LEDs toward your skin. It should be tight so that the sensor is always in contact with the skin but not very tight to the point of making it difficult for you. It should hold in place essentially to your skin and not move. No need to strangling your arm 🙂

You can position it at 3 different levels on your arm:

  1. On the wrist, on the other arm similarly to a watch (put it on the opposite wrist to your watch, it works fine)
  2. Mid arm before your elbow
  3. On the top of the arm on your biceps

This last positioning is more for sports like running I think. You can hide the sensor under your shirt for example. However if your muscles are contracting, it can be more constricting… Try various place. The only constraint is that the LED should face the inside or outside of your arm, where there are veins to get good measurement. Do not forget to remove the plastic protection on the LEDs… I forgot and was wondering why I had measurements of 85-90bpm at rest… it was because of the plastic sheet !

Using it during workout

This is still ongoing for me but the plan is to replace the chest strap entirely. All of my workouts except maybe ultra races or long hikes are less than 8 hours. Here is what I found so far:

  • For gym workout, strength training, … it’s simply superb. You forget about it, don’t need to have your phone nearby. I tried in the past to do strength training with the chest strap and it’s just hell. Try to do simple things like planks and the strap is not tight anymore, … Here I put the Rythm+  on the lower arm and forgot about it 🙂
  • Running outdoor, I tried few positions for the Rythm+ on the opposite wrist and connected it to the Fenix 3 via Ant+.
    • First run, I went for 1h15 outdoor in a light haze in the middle of the afternoon. Total 13km.
      I ran for 40mn with the Rhythm+ on my right wrist and it was fine until I felt it was too tight. Unlike the left wrist, I don’t have habits and tolerance for a tight wrist device (watch, heart rate, …). I had to untie it to tie it back, hence the drop of measurement (first one). After this, I moved the Rythm+ onto the top part of my forearm, below the elbow. After few kilometers, maybe due to sweat and vibration, it did slide down hence the lack of measurement. When I put it back, it was tight enough and it did not move anymore.
    • My second run was the next day in Putrajaya for a 20m LSD. I decided to wear the Rythm+ on the right wrist, less tight than the day before. It was fine for the whole duration. Looking at the heart rate,there were few drops. I can’t explain these drops. I’ll run more tests. If you look at the 2nd graph, where I added cadence and pace, you can see that during these drops (to value 0 bpm), I was moving. To be monitored. The only difference today was that it was less tight and I had my LifelineID just beside the Rythm+. I think it might be the tightness as when it was tighter there was no drops (unless removing the sensor).

Conclusion

I think it’s a good device if you can’t handle the chest strap. If you rely on the metrics from Garmin HRM (oscillation, …) you must use the chest strap. The Rythm+ will not provide any of these.  I don’t really need these so that’s OK for me. The price I got it was good. At 129AUD instead of 98AUD, I’m not sure I would buy it. This however has to be put in perspective: a Garmin chest strap is 80 AUD and the HRM is 100AUD (for the sake of comparison). I don’t know the prices in Malaysia, but the Rythm+ is not too shocking. As you compare it with the normal chest strap, it’s basically 80AUD vs 98-129AUD. Hopefully this gets integrated in the next Fenix watch, so that you don’t need a second device or a chest strap.

Resources

  1. DCRainMaker review of the Rythm+, as usual VERY detailed. A reference. It gives comparison graphs for workouts between a HR strap and the Rythm+: http://www.dcrainmaker.com/2014/05/scosche-antbluetooth-optical.html
  2. Scosche Rythm+ product page – http://www.scosche.com/rhythm+
  3. JB-Hifi product page, apparently I was lucky and bought at the right time, it’s back to 129AUD ! https://www.jbhifi.com.au/ipods-docks-fitness/scosche-rhythm/rhythm-heart-rate-monitor-with-armband-works-with-popular-fitness-apps/617900/
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