Mio Link Wrist Heart Rate Band

A Strapless HRM?

Those who have been following me know that I have a love/hate relationship with my heart rate monitor. When I first got my first GPS running watch (a Garmin 410), it came with a Garmin HRM 2, soft heart rate strap. This strap, while looking comfortable, dug a hole into my chest. It was so bad that I needed to put Band-Aids, duct tape, and gauze on my strap and chest. In fact, the problem was well documented by DC Rainmaker. I also had issues with spikes and GPS dropouts.

Garmin Forerunner 410. My first GPS Watch.
Garmin Forerunner 410. My first GPS Watch.

I contacted Garmin about the problem. At that time, they had released a new strap which was supposed to be more comfortable and had an updated heart rate module. I was sent this new strap free of charge under warranty. This was the HRM 3 strap. The strap was more comfortable and had silver threads weaved into it to prevent static buildup under exercise shirts. It was also machine washable. Clutch.

Unfortunately, I had inconsistent results with my heart rate monitor as I ran or biked on cold or hot days. Sometimes, the issue came at the most inopportune time such as during a triathlon race.

What happened to the HRM? Not cool from a pacing standpoint.
Heart Rate Monitor Issues in a Race.

Read on for more.

Exploring Options

I’ve read about the Mio Link and was also considering a different brand of soft chest straps. One day while waiting at the airport for a business trip, I noticed a very fit man sitting next to me with a Garmin Fenix 3 on one wrist and the Mio Link on the other. We began chatting and come to find out, he had recently completed Ironman Texas. I picked his brain a bit about it and he loved the device. Like me, he had issues with the chest straps over long distance endurance events and needed something different. As you’ll note below, his only complaint was the battery life. Battery life is 8-10 hours. This is not enough for most people completing full Ironman races or some ultra marathons. In fact, his Mio battery died with 7 miles left in his Ironman Texas marathon.

After exploring the Mio Link and other chest straps as options, I decided to pick one up from Amazon for $80. Couldn’t beat it.

Meet the Mio Link

The Mio Link is a successor to the Kickstarter backed Mio Alpha (a much larger device with additional features). The Mio simultaneously broadcasts over Bluetooth and ANT+ protocols. This means that the device can be paired to smart phones, bluetooth cycling head units, and virtually all ANT+ fitness products including those made by Garmin.

Mio claims EKG accurate heart rate data. In fact, the technology they use is licensed by Phillips Healthcare.

Inside the box are three items of note. You get a silicone band, the sensor which fits in the band, and the USB charger. There are two sizes of bands, but one must be selected upon purchase. I grabbed the large size as I was right in the middle of the Small/Medium and top end of the large wrist diameter.

What comes in the box
What comes in the box

The device is pretty simple. Bright green LED lights shine into your skin where a photo/optical sensor looks for changes in how the light is absorbed. This medical technology has been around for YEARS and known as a Photoplethysmogram.

Sensor off
Sensor off
Sensor on. Green LEDs plus photo sensor = Heart Rate
Sensor on. Green LEDs plus photo sensor = Heart Rate

The instructions clearly indicate that the device should be worn 2-3 finger widths up the arm (towards the elbow) from the bony part of your wrist. The band should be tight…tighter than you’d wear a watch. Essentially as the entire device requires a “closed circuit” of light, any light that enters from the environment will cause funky readings.

Place it higher on the wrist for accurate measurement
Place it higher on the wrist for accurate measurement

The device can be paired with a smart phone which allows further configuration of the device. The app can be used to track activities or configure the device.

Main Mio App
Main Mio App
A Mio is paired to the phone
A Mio is paired to the phone

The Mio app allows you to specify how you want the LED on the front of the device to work. In my case, I selected the 5-zone settings.

Overview of options and settings
Overview of options and settings

By selecting the 5-zone setting you can customize your heart rate zone and have the LED change color based on what zone you are in. As an example, if my heart rate was 165, the LED would flash yellow.

Setting custom HR zones
Setting custom HR zones
Top side. LED shows configurable HR Zone.
LED shows configurable HR Zone.

Mio suggests wearing the device next to your fitness device if possible. While ANT+ supposedly can be transmitted 5-10 feet, it has a problem transmitting through the body. For some individuals that have large “arm swings” while running, dropouts have been known to occur. This means that Mio recommends having both a watch (like the massive Garmin Forerunner 910xt) AND the Mio on the same arm. It isn’t the most ideal setup, but it sure beats the pain of a chest strap.

Mio plus Garmin Forerunner 910xt
Mio Link plus Garmin Forerunner 910xt

Testing it Out

My first order of business was to test how “close” the Mio was to the chest strap for accuracy. I pulled out my Garmin bike computer and had that paired with my old HRM 3 chest strap. I paired the Mio to my Garmin 910xt and then watched both devices for a few minutes. After a minute or so, the Mio stabilized and was within 2-5 beats per minute of the chest strap. For me, I’d call this good enough, but in some cases, heart rate zones can be very narrow, so it might take some additional testing to understand how close they are.

I took the Mio out for a run and a ride on my triathlon bike. Mio suggests when cycling to have the device on the underside of your arm as sometimes the way people hold handlebars causes light to enter the sensor and again, causes dropouts or weird readings. So, how’d it go.

Run

I went out on a hot day while slightly dehydrated. I expected the heart rate to be elevated. After a minute of the heart rate stabilizing, I began running and barely noticed the device on my arm. Throughout the duration of the run my heart rate was tracking exactly as I felt on a RPE scale and how previous runs of that pace, temperature, and intensity would track. No issues.

First run with Mio Link. Heart rate matched RPE and other runs like this.
First run with Mio Link. Heart rate matched RPE and other runs like this.

Ride

I wore the device inverted in that the sensor was on the inside of my arm as recommended by Mio. Similar to the run, the heart tracked exactly as I expected it to based on speed, intensity, terrain, and whether I was drafting or pulling on our ride. Towards the end, however, I noticed slight discomfort near the clasp. However, as I was riding my triathlon bike and was on a group ride, I was on the “hoods” far more than in the aero bars. In a typical training session in the aero position, I would expect far less issues here.

First ride with Mio Link. Heart rate matched RPE and other rides like this.
First ride with Mio Link. Heart rate matched RPE and other rides like this.

Pros and Cons

ProCon
  • Cheap
  • More comfortable for men and especially women who have issues with chest straps
  • Dual broadcast over ANT+ and Bluetooth
  • Has been known to track heart rate while swimming if worn on same wrist as watch
  • When paired with smartphone, can add heart rate to activities tracked on the phone
  • Recommended to be worn on same arm as watch
  • Battery life only 8-10 hours
  • Unit requires another device to track activities (Smartphone, watch, or computer)
  • Some people with heart medical conditions may not work properly
  • Might get uncomfortable on bumpy bike rides

Would I Get it Again?

Simply put…yup. Thus far, the Mio has been more comfortable than the chest straps ever were. I also found the Mio, when paired with a smart phone, makes for a great and fast way to measure your resting heart rate in the morning before getting out of bed. You can buy your own Mio Link here.