I’d been eyeing the Mio Link Optical Heart Rate Monitor for a few months having seen the Mio technology (which was developed in conjunction with Philips) slowly show up directly integrated in to more and more watches like the Garmin Forerunner 225 and TomTom Cardio, so about 6 months ago I decided to pull the trigger and order one.
Disclosure: This post contains affiliate links, which means I may receive commissions if you make purchases after clicking on any product links. The device in this review was purchased by me, at full price, and was NOT provided by Mio.
For years, like many of you, I was using a chest strap heart rate monitor. There was really nothing wrong with my chest strap (except the Garmin HRM-Run strap which made me bleed every time I ran with it), it was just always a minor annoyance. I was constantly having to adjust it on the run since it would move around and I just got tired of dealing with it. On the plus side, the battery life was great and it worked as expected.
Before I get to the review, a little background on optical heart rate sensor technology. In a nutshell, an optical heart rate monitor shines light (usually green and/or red LEDs) through your skin and then measures the refracted light. That information is then used to determine your heart rate after applying some algorithms to eliminate “artifacts” like the movement of your arm. In contrast, a standard chest strap heart rate monitor measures your heart rate by detecting the electronic signal emitted by your heart through your skin.
The Mio Link retails for $79 which is a great price for this product considering it is an optical heart rate monitor. This price puts it right around the middle of the price range for non-optical heart rate monitors. For example: (Retail prices listed, actual prices may vary)
Garmin Heart Rate Monitor – $60
Garmin Premium Heart Rat Monitor – $69.99
Garmin HRM-Run – $99.99
Polar H7 Bluetooth Heart Rate Monitor – $79.95
Wahoo TICKR – $49.99
Wahoo TICKR Run – $79.99
Wahoo TICKR X – $99.99
The only competitor with an optical heart rate monitor is also priced the same as the Mio Link:
Scosche Rhythm+ – $79.99
The Mio Link supports both ANT+ and Bluetooth Smart (4.0), which means it can be connected to any modern smartphone/tablet and almost every GPS watch on the market today. In fact, because it has both protocols (ANT+ and Bluetooth Smart), it can actually be connected to two devices simultaneously if the need ever arises.
According to Mio, here are the supported devices:
SMARTPHONES AND TABLETS
iPhone® 4s/5/5c/5s/6/6 plus
iPod® touch 5
Samsung Galaxy s® 4/5
Samsung Note® 3
Google Nexus 4/5
Android 4.3 (Jelly Bean) and higher with Bluetooth Smart (4.0)
Garmin Forerunner (all models)
The Mio Link can be ordered with two different sized wrist straps (S/M and L), depending on the circumference of your wrist. Mio provides a convenient sizing chart, although it’s difficult to find on their website. Print the chart, cut out the measuring strip, wrap it around your wrist, and order the size that fits.
Since the Mio Link relies on light to detect your heart rate, it is meant to be worn snugly on your wrist so ambient light can’t get in between your wrist and the device and interfere with the readings. The Mio Link strap is made of soft silicone and includes a number of closely spaced holes so you can get the most comfortable fit possible. Overall, once I put the Mio Link on, I don’t notice it on my wrist.
I do get asked about which wrist to wear the Mio Link on, and I’m not sure it makes that much difference. I wear it on the opposite wrist from my watch and I’ve never noticed a connection problem. My advice would be to wear it on whichever wrist feels more comfortable for you.
Using the Mio Link
The Mio Link has a single button and a single multicolored LED which is used to indicate status and your heart rate zone. After putting the Mio Link on your wrist, hold down the button on the top of the device for a few seconds and the LED will light up indicating that it is powered on. The first time you use it, you need to sync it to your device following the instructions for your device or app. For each subsequent use, the Mio Link should connect to your device automatically once it is powered on.
While running, the multicolored LED will blink a specific color every few seconds depending on what zone your heart rate is in, which is configurable via the Mio Go app. I find the blink interval to be fairly long and I have a hard time remembering which color corresponds to which heart rate zone, so the only value in this feature in my opinion is showing that the device is still powered on and detecting your heart rate.
When you are done using the Mio Link, hold down the button for a few seconds and the LED will display a solid color and then power off.
Mio Go App
Mio provides a free companion app called MIO GO for Apple (iTunes)and Android (Google Play) which is fairly limited in functionality relative to other apps like Strava, Runkeeper, Wahoo Fitness, etc. but works well, all things considered. The app will let you do the following:
- Connect your Mio Link to your device and track a workout while capturing your heart rate data, with our without GPS.
- Display the battery life of the Mio Link using the familiar battery icon with 1-5 bars indicating relative remaining battery life
- Display your heart rate
- Configure heart rate zones (they are initially calculated based on your profile data which includes date of birth, height, weight, and gender)
- Update Mio Link Firmware
- Sign up for the Mio newsletter
Updating Mio Link Firmware
The Mio Go app is necessary in order to update the firmware on the Mio Link since the device does not have any direct internet or wifi access itself. In order to update the firmware:
- Connect the Mio Link to the Mio Go app
- Select the hamburger icon (the 3 lines in the top left corner)
- Select Help
- Select Software Updates
- Click Start Update
Once the firmware has been updated, the Mio Link will turn itself off, so you’ll need to turn it back on if you intend to use the device right away. One oddity with the firmware update process is that the firmware will be updated, even if it has the most up to date firmware. It only takes a few seconds, so it’s not a big deal, but it wouldn’t be difficult for Mio to build in a mechanism to prevent this from happening.
The Mio Link has a claimed battery life of 6-8 hours, and in my experience this has proven to be consistently true. The few times I’ve run longer than the battery life lasts, the device died around the 7 hour mark every time.
Charging the battery is a simple process. The included charger has a USB plug on one end so you can recharge from any USB port, or from the wall if you have a USB adaptor (I use an extra one from my iPhone with no issues). You simply plug in the charger, lay the Mio Link on the charger which has an embedded magnet making sure the charging connectors line up, and away it goes. I haven’t tracked the amount of time it takes to fully charge, but it’s relatively quick and I’ve never had an issue with it not being fully charged when I’m ready to go for a run.
In my experience over the last 6 months, the Mio Link seems to be as accurate or more than my Garmin Chest Strap. I’ve done a number of test runs this winter in order to quantify the accuracy, and in every case, the Mio Link heart rate data was virtually identical when I compared the data.
In order to do my test, I used my Garmin chest strap paired with my Garmin Fenix 2, and my Mio Link paired with the Wahoo Fitness app on my iPhone 6S Plus simultaneously. The reason for using Wahoo Fitness instead of the Mio Go app for my testing is that Wahoo Fitness allows a TCX file to be exported to Dropbox, which is critical for analyzing the data. TCX files capture GPS track points with the heart rate data, while GPX files only capture GPS track points without the heart rate data.
In order to perform my tests:
- I went on a number of runs of various distances in various conditions (temperature, route, intervals, etc.)
- Downloaded the TCX files from Garmin Connect and Wahoo/Dropbox
- Parsed out all the heart rate data points (and deleted the time stamps that didn’t line up, which was the result of not being able to start/stop both devices at the exact same time)
- Imported and overlaid the data as a graph in Excel.
Here is the data from one of my tests that you can see for yourself. The spike in the beginning is due to not getting the contacts on the Garmin chest strap wet before starting my run, so it took a few minutes to pick up my heart rate accurately and settle in.
Based on the consistency of my testing results, I can confidently say that outside of medical or life threatening reasons, the Mio Link is as accurate as a chest strap, if not more accurate in some cases.
I haven’t personally experienced any issues with the Mio Link, but a number of people online have complained about accuracy, or more specifically, the Mio Link locking on to their cadence instead of their heart rate. Mio has worked hard to fine tune their algorithms to remove this movement “artifact” and in many cases (such as my own) there is no problem. There are a number of potential reasons for poor accuracy:
- Skin Tone – There are reports that the darker your skin, the harder it is for the green LED lights to penetrate your skin and read you heart rate. Unfortunately there isn’t much you can do about this.
- Too Loose – This is a more common issue in my experience. People have a tendency to wear the device loose, like they would a watch. In order for the Mio Link to work properly however, it must be snug against your skin to prevent any ambient light from interfering with the device.
- Too close to the wrist bone – Bone interferes with optical heart rate monitors due to the density (the light gets absorbed and doesn’t refract back to the device to read your heart rate) so it’s best to keep the Mio Link as far away as is comfortable from your wrist bone. Another alternative, and one recommended by Mio, is to wear the device so the sensors are underneath your wrist.
- Outdated firmware – Depending on how long the Mio Link was sitting around before you purchased it, the firmware may be out of date. Mio does update the firmware to improve detection, accuracy, and other items so you should make sure you update the firmware and see if that resolves any issues you may be experiencing.
In summary, the Mio Link was a great purchase and it has replaced my chest strap 100% of the time when I’m running or mountain biking. I constantly recommend the Mio Link to my running friends. If you are using a chest strap today, you should give the Mio Link a serious look and I think you’ll find it’s a game changer, even if you think a chest strap doesn’t bother you. I’m convinced you just don’t know what you are missing.
- Device Compatibility
- Weak charger magnet
- Battery life
Do you use an optical heart rate monitor? Let me know your thoughts in the comments below.