Mio Fuse Review – An Optical Heart Rate Monitor & Activity Tracker Rolled into One

Activity trackers have become big news over the past couple of years with rapid expansion in the number of models on the market and range of data that they are capable of recording. Things have moved a long way since the days of simple pedometers and there are now devices out there which monitor things like sleep quality, calorie expenditure, skin temperature and perspiration levels.

There are also a small but growing number of trackers which include optical sensors to measure heart rate during activity and when at rest. In my view, this makes them much more useful for those who take exercise more seriously as heart rate data provides vital information on training intensity and recovery as well as just volume.

Mio are a well known for their of optical heart rate sensors which can be found in their own devices like the Alpha sports watch, the Link which I reviewed last year and also in watches manufactured by other brands like TomTom and Adidas.

The Fuse is Mio’s first foray into the activity tracker market and it uses the same sensor as their other products but adds an internal accelerometer to detect movement along with an LED display.


  • Activity tracker
  • Estimated calorie expenditure
  • Customisable daily goal
  • Optical heart rate monitor
  • Exercise mode which measures heart rate, distance travelled, pace and duration
  • Displays customisable heart rate zones
  • Smartphone integration via Mio GO App (iOS and Android)
  • Water resistant to 30m
  • Stores 2 weeks of daily activity and 30 hours of exercise data
  • Ant+ & Bluetooth Smart connectivity with GPS watches & Cycle Computers (compatibility list here)
  • Battery life of approx 6-7 days with 1 hour of workout time per day

Unboxing and First Impressions

As with Mio’s other products, the Fuse is nicely packaged and well presented. The box includes the device, charger and a quick-start guide with more detailed instructions available to download from their website.

The device itself is quite chunky and a little larger than the Link but not so much so that I would feel self conscious wearing it. The combination of a sleek shape and a retro-looking display is quite cool in my opinion but without being extrovert.

The Fuse is activated by touch-sensitive buttons on the strap which are marked by braille-like raised areas. The buttons can only be controlled when the wrist is horizontal which takes a bit of getting used to initially but Mio have added this feature to prevent accidental activation.

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Mio recommend that the Fuse is worn at around 2 inches from the wrist crease where the arm becomes more fleshy so that the sensor can get unbroken skin contact with no light leakage. Correct positioning is important to ensure you get an accurate reading and as with the Link, you may need to experiment a little to find our what works best for you.

The Fuse is comfortable to wear and the strap can be finely adjusted to suit the size of your arm. It is secured in place by a couple of pins (see picture) and these have a habit of coming undone accidentally. This is an issue that is shared by the Link and it only happens occasionally but I’m a bit surprised they carried it over to the Fuse as I’m not the only one who has commented on it.

Mio Fuse Strap

Strap Closure



It’s worth taking the time to set up the device properly before using it to ensure that accuracy of the readings and this is achieved via the smartphone app. I’m an iOS user and I found the process of entering information and syncing the settings with the device very straight forward.Device setup

Some General Thoughts on Activity Tracking

I’ll admit that part of me always scoffed a little at the idea of having an activity tracker as I consider myself a relatively fit and active person so I never felt like I’d have much use for one. However, like so many of us these days I spend around 10 hours a day 5 days a week sat on my backside either driving or at a computer and tracking my activity has made me realise that on a non-training day, there are long periods of time when I’m hardly moving at all.

This has been a real eye-opener and it’s made me think a lot about how inactivity affects my mood and stress levels. Using the Fuse has helped me make a conscious effort to do something on rest days and I’ve noticed a tangible improvement in my sense of wellbeing as a result. The device serves as a handy little reminder of this and I would imagine that there are lots people with similar lifestyles to me who could benefit from it.

Device Accuracy & Performance


The buttons on the Fuse are generally intuitive and easy to use. I’ve had the odd occasion where the start/stop button didn’t seem to respond to my attempts to press it when my hands are cold but other than that, I think the controls are well thought-out.

Heart Rate Monitor

I’ve had extensive experience of using Mio’s optical heart rate sensors with the Link and the Fuse carries all of it’s good points but also one niggle.

Once you’ve found the best position to wear it, heart rate data is largely accurate and consistent with readings from a chest strap but much more comfortable and convenient to wear.

The niggle comes when the Fuse will occasionally start displaying my running cadence in place of my heart rate. I don’t know the exact mechanism for this but I’ve read that other users have had the same issue and it’s something to do with the impact forces causing interference with the reading. I should point out that it only happens for a few moments with a frequency of maybe once every other run and the device works fine for the remaining 98% of the time.

There is a single LED to indicate your heart rate zone and the vibrating alert informs you when you have transitioned from one zone to another. This is very nicely executed and super useful for HR interval training. Mio Fuse HR Zone

Running Distance & Pace

Running distance and pace are calculated via the internal accelerometer. I’ve included some data samples below to compare accuracy between the Fuse and my Ambit2 GPS watch. You will notice that the Fuse has underestimated both the pace and the distance which is consistent with almost all of the workouts I recorded during the month-long test period. Whilst I think it would be good if Mio could refine the internal algorithms to improve this, I suspect that most people who want more accurate data will be pairing it with a GPS device whilst exercising anyway.

Another point to note is that the the 196 maximum heart rate shown below is an example of when the device was picking up my footfall whilst running downhill but as I mentioned above the glitch only happened for a few seconds. It would actually be great if the Fuse displayed running cadence (intentionally) as one of the outputs as I feel sure that the accelerometer could record this.

Workout screen 1

Fuse / Mio GO Data


Movescount screenshot

Ambit2 Data

Activity Tracker

The activity tracker allows you to set goals for your daily movement and as with the distance and pace data I’ve referred to above, I’ve noticed that the Fuse has a tendency to slightly under-record the number of steps that I take. Obviously, you are going to want a device like this to be as accurate as possible but personally, I feel that having a general overview of how active you have been on one day relative to another is way more important than knowing the precise number of steps and the Fuse does this just fine.

The lack of sleep tracking is a bit of a stand-out omission relative to many of the Fuse’s competitors but I’ve read rumours that they are working on an update which will add this so we will have to wait and see.

External Device Pairing & Connectivity

The Fuse enables you to connect to sports watches and cycle computers where are Bluetooth Smart or ANT+ enabled (compatibility chart here).

As with the Link, Mio recommend that the device is worn on the same arm as your GPS watch when pairing the Fuse via ANT+ because the signal cannot travel through the body and therefore gets disrupted by arm swing whilst running. The Link took a bit of criticism for the power of it’s ANT+ transmitter and I did find that pairing it with my watch was occasionally a bit temperamental. Mio claim to have improved this with the Fuse which for me, has made a noticeable difference and it pairs with my Ambit first time every time. You’ll notice from the picture below that the reading on my watch tends to lag behind the Fuse by about a second meaning that there is sometimes a 1 BPM difference in the figures but I don’t consider this a problem.

Mio Fuse Pairing

A lot of Link users commented that they would prefer it if they could wear the device on the opposite arm to their ANT+ watch and I gave this a try with the Fuse on a few occasions to see if the improved signal strength would make it possible. This proved unsuccessful and I noticed regular drop outs. It would be unfair to criticise the device for this as it is against the manufacturers instructions but I thought people might be interested to hear if it worked all the same.

Bluetooth Smart performance is good and I’ve had no connectivity issues when pairing it to fitness apps on my iPhone, even with the phone in my bag and the device on my wrist.

One thing I found really cool about using the Fuse with my Ambit2 is that it gives you an additional visible display which means that you can free-up a data field on the watch. If you are pairing it with a smartphone, it means that you can have heart rate and (moderately accurate) pace / distance data visible from your wrist all the time without having to look at your phone on the move (this is always awkward).

Mio Go App and Integration

The Mio Go App allows customisation of the settings as I’ve mentioned above and It also allows you to download saved workouts and activity records from the device. The daily activity screens within the App are pretty good and allow you to see whether you have been hitting your targets. The workout screens display the data for each time you have exercised but the heart rate graph is small so it’s quite tricky to do any kind of detailed analysis of the information from inside the app (should you want to).

Unfortunately, you can’t currently download the saved data to any third-party apps which would allow you to view the work out information on a computer in more detail. This is a bit of a bummer and it limits how useful the information is if you are using the Fuse as a stand-alone device without connecting it to a watch or smartphone whilst exercising. I understand that Mio are working on integration with other platforms so I’d keep an eye on their website and social media feeds for news on this.

Battery Life

Mio Claim that the Fuse battery should last approx 6-7 days based upon 1 hour of workout time per day and this is completely consistent with my findings. If you are looking at using the device for ultra-distance events, it should  be noted that the battery will record continuous HR for 7-10 hours with the display permanently on, but up to 20 hours with it switched off and this is a big improvement over the Link.


I’ve got a couple of relatively minor niggles with the Fuse but overall I think it’s a great piece of kit which will be even better once the Mio Go app is refined and / or the device allows you to download data to third party software for more detailed analysis of exercise data. Again, this won’t be an issue for those who aren’t interested in delving more deeply or users who are planning to connect the device to a GPS watch / Smartphone whilst exercising.

The RRP is £130.00 and I think this is about right in comparison to it’s competitors. The activity tracking is great but even if you are just looking for a Bluetooth / ANT+ Optical heart rate monitor, I think it’s worth considering spending the additional money on the Fuse over the Link because of the extra battery life, in-built display and vibrating alarm.

This product was provided by the manufacturer as a test sample. Please see my gear review and advertising policy for more information.

Where to Find One

The Mio Fuse can be purchased via Amazon

I make every effort to ensure these reviews are as objective and honest as possible to help you decide if a product is right for you. This takes me a lot of time and effort and if you are interested in a product I have reviewed, you can help me keep the site going by making purchases through the links and adverts at no extra cost to yourself. Thanks for your support.

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Do you have any questions or comments about the Mio Fuse? Please leave your thoughts below!

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  1. Denise says:

    Hi wonder if you can help please. I have been trying to the firmware on my Fuse but as it was taking hours (literally) to do so, I disconnected. Now the display is simply featuring the M (errr for Mio I guess) and the app can no longer make a connection. Any ideas?

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