John Galea's Blog

My blog on Gadgets and the like

Mio Link wrist heart rate monitor

I saw this product recently and it caught my attention. Wrist based heart rate monitors have never been any good. There`s too much going on near the wrist to be accurate. Witness the joke of a heart rate monitor on the Samsung Gear that only works if you sit still and push it firmly against your wrist, useless. Add in activities like mountain biking into the mix and you take a difficult situation and you make it perilous to get reliable date out of. This company seems to be a pioneer in the space so I thought I’d give them a try. If your a skimmer, I would not recommend buying this product. Read on for details.

Physically the device looks like a fitness tracker. It’s an innocuous rubber band. There is only one switch and one LED on it and it blinks different colors based on the zones your heart rate is in. A nice feature. There is an Android app that allows you to tailor your zones. The rubber band includes a locking mechanism that insures it’s snug on your wrist and isn’t going anywhere. Also the loose band can’t get caught on anything. The band comes in two sizes. Based on length I bought the smaller one (I have a small wrist) which turns out to be a mistake. Directly from their manual “If you use Mio LINK for biking, wear it higher on your forearm, since bending of the wrist may affect the heart rate reading. For cyclists or users with concave wrists, try wearing Mio LINK on the underside of your forearm.” Of course I didn’t see that before I bought it. Wearing it on the forearm would take a much bigger strap. And frankly, if I was going to wear it on the forearm I wouldn’t buy the Mio, I’d buy the Rhythm+ from Scosche.
The electronics can be removed from the rubber wrist band to allow you to clean it as well as replace it. One of the times I was using it I tightened it too much and that caused it to partially come out of the band and thus loose contact with the skin.

Battery life is excellent. I got over 7 1/4 hours on a charge.

The device supports both Ant+ and Bluetooth Low power so you need a newer phone but it can connect to multiple devices at a time. I did run into a problem where my Garmin Foretrex 401 had issues with two Ant+ heart rate monitors (the Mio and my Garmin chest strap) and it kept bouncing between them every second and beeping annoyingly. I suspect that was because I had paired the Foretrex with both. But I was surprised it didn`t lock on one and stay on it. I also had issues staying connected to the Mio in a crowded environment with numerous bluetooth smart devices present.

On a brief walk I compared the Mio with a Zephyr hear rate monitor. I saw constant large differences. I was wearing it on the wrist on my left hand, right side up. The Mio got a (max/avg) 134/107 vs the Zephyr 112/110.5 for a whopping difference of 20/3%. Yikes. Zephyr raw data, Mio raw data.

This caught my attention enough I decided to focus on the reliability of the data. I went out for a mountain biking ride and recorded the data with the same app (RunGPS) with two different phones. I wore the monitor on my left hand, comfortably tight, at the wrist, facing up. I wanted to eliminate the variability of different apps. The data was partially spoiled because for some reason the Mio lost connection with my phone halfway through. This in turn through off the max/min/average and calorie count of the data.

This got me wondering about the accuracy of the Zephyr. So I did a comparison between my Zephyr and my Garmin Ant+ HRM. The Zehpyr data was (Min/Max/Avg/Calories) 55/93/68.8/92 Vs the Garmin at 55/99/69.5/95 for a difference of 0/6/1/3%. So the two chest based devices seem pretty darn close. So then I did a graph of a new data run between the two and found these two compared fairly well. See the graph.
garmin-zephyr raw data

So I did the same basic comparison this time between the Garmin and the Mio. (Worn on the left wrist, upside down, just walking) The data showed a lot more variability from the Mio (in comparison to the Garmin/Zephyr). Stats wise it came up with (min/max/avg) 60/116/73.3 for the garmin Vs 50/121/74 for the Mio for a difference of 17/4/1%.
garmin-mio raw data
At times the Mio just seemed to completely loose any semblance of accuracy.

I did another one where I was mostly inactive. The numbers came up as (Avg/Max/Calories) 67/124/157 for the Mio Vs 68.9/114/181 for a difference of 3/8%. Here`s the graph comparing data:
mio-garmin-2 raw data

And yet another one, this time with the heart rate monitor on the left facing up.

If this had happened once I would write it off. But it happened numerous times. During riding, walking and even inactive times (just sitting). Now maybe for some people this device works well, but for me it just is not reliable. Maybe it`s my small wrists, maybe my coloring, no idea.

I contacted Mio customer support. They were convinced I had a defective unit, so they sent me another one. It came with basically the same issues (inaccuracies). So I have returned my Mio Link (sadly). Not convinced? Here are a few graphs from the second unit:

So in the end the physicals etc are irrelevant (although I must say this is hands down the most comfortable heart rate monitor I`ve ever worn). If you can’t count on the data to be accurate then what in the world would be the point of buying one of these? I have to say I am thoroughly disappointed in this product.

August 15, 2014 - Posted by | Electronic gadget reviews

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