Review: Mio Fuse

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What is it?  The Mio Fuse is an activity tracker and heart rate monitor.  It is a pretty nifty little device.  As an activity tracker, you can set goals, monitor your heart rate, and keep track of steps, calories and distance.  It will show you, via the app, how many steps you have taken, and how many you need to reach your goal. The heart rate monitor is an optical sensor.  Meaning it shines a little light on your skin and the sensor pick up heart rate.

My interest in the Mio Fuse is primarily as a heart rate monitor.  As an athlete and coach who trains with heart rate based periodization, heart rate is an important piece of information.  Each athlete has their own individual heart rate zones.  No two people are alike.  Using a standard formula for everyone does not produce individual zones and is not useful for training (and in fact could be detrimental, as too much time in the wrong zone, or too high a zone can lead to burnout and injury).  I want to run in specific zones in my own training, and when I write workouts for athletes, they are assigned zones based on the intent of the workout (endurance, tempo, or recovery for example).  As a woman prone to chafing, I have some serious issues with the Garmin heart rate strap.  For me, it causes painful chafing under the sensor (for other people it can cause chafing anywhere under the strap itself).  Its not possible to put anti-chafe under the sensors, as that interferes with the signal.  The Fuse seemed to be the solution to this problem and I was excited to give it a try.

The Fuse comes in two sizes, depending on the size of your wrist.  I chose the small size and as you can see, even while wearing the Fuse high on the wrist (more on placement later), I have enough extra band.  The Fuse has 3 buttons, or touch points.  The two on the side scroll through time, calories, steps, distance and goal.  It will also display your heart rate.  The midde touch point is for finding your heart rate and starting, pausing, and ending an activity.  The Fuse finds heart rate pretty quickly.  Touch the middle point, it will say “find” then wait for heart rate to pop up.  To start a workout, touch the same point again.  It will read “go” as the timer starts.  Touch it again to pause, then hold it down, when paused, to end an and save an activity.

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Pairing the Fuse with the Garmin was easy.   Put the Fuse on and find your heart rate.  Then set your watch to scan for the heart rate device.  It pairs quickly, and since the first pairing,  Garmin finds it right away (no scanning again required).  Heart rate will then show on your Garmin/watch screen.  The Fuse does not have an “always on” screen, which I would like, but I imagine this is a battery life issue.  You can customize your zones in the app (which “talks” to the Fuse via Bluetooth) and the Fuse will vibrate for a split second to let you know when you have changed zones.  It will display heart rate at that point, so in that way you can see on the display when you putting out too much heart rate effort, or not enough, and stay in your proper zones.

The first run I did with the Fuse, I experienced long dips (into the low 100s when I should have been in the high 140s), and conversely, spikes into the high 170s/180s when I should have been high 140s/low 150s).  This happened after about 3 miles of perfect heart rate numbers (compared to rate of perceived exertion, which I know quite well, having been a heart rate based athlete going on 5 years now).  This was disappointing.  I then did a run wearing two Garmin watches (910xt and 110).  The 110 was paired to the strap and the 910xt was paired to the Fuse.  Here are the results.  You can see the Garmin strap (top in both examples) is accurate, whereas the Fuse has dips and long surges.

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I called Mio and left a message (there is an option for a call back, but if you just let customer service ring it will put you to voicemail).  Surprisingly I received a call back in a few minutes.  The rep made a couple suggestions.  One, put the Fuse on your wrist, with a little room on the strap. Then “snug” it up your wrist about 3-4 inches.  Let the strap conform to you, instead of putting it on tight.  The Fuse is meant to be worn high on the wrist, as it needs enough surface area to get an accurate reading.   Being female with small wrists, I need to wear it on the high side to get accuracy.  He also suggested wearing it on the inside on the wrist, although I did not find that in practice to be accurate.  The last suggestion was to wear it for a few minutes before pairing to the Garmin and starting a workout. On my next run, I did as suggested and the Fuse was accurate.  The take-away – wrist placement is key for accuracy.  I find I have to wear it high and a touch off center.  It does sometimes slip down and needs to be gently nudged back into proper position.  After wearing it for a few more runs, if it is place in the right spot, it is highly accurate.  When it deviates (either error in putting it on or it slides around), that is when the dips and spikes occur.

The Fuse will record distance a bit low.  For example, an 11.2 mile run on the Garmin read as 9.69 miles on the Fuse. The Garmin had another at 11.01 mi. with the Fuse reading 8.92 mi.  But not always.  A different time, Garmin had 10.22 mi. to the Fuse at 10.8 mi., and my 10k (with mile warm up) came up as Garmin 7.34 mi. and Fuse 7.35 mi.  Again, not a big deal for a runner using the Fuse paired with a GPS watch.

I also used the Fuse on the bike for trainer rides.  The weather hasn’t been conducive to outdoor riding so I have tested it indoors only.  The accuracy is 100% on the bike, most likely because your arms are in a more fixed position than when running.  The accuracy is the same whether the ride is recovery (low HR), endurance (Zone 2) or tempo and intervals (pushing into Zone 4 and beyond).  This is very encouraging and the Fuse getting very sweaty did not affect accuracy.  Again it paired easily with Trainer Road via Ant+.

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The Fuse was a pleasant surprise on the swim.  Unfortunately, the Garmin 910xt does not have an available heart rate data field under the swim function.  So there was no way to to pair it for a swim, and no way to get a heart rate graph from Garmin Connect.  I wore the Fuse by itself in the pool.  It stayed in place pretty well, and the heart rate readings were accurate as compared to perceived exertion.  The distance is not correct, but that doesn’t really matter, as athletes are typically following a written swim workout.  One swim I did was 2500 yards, it recorded .91 miles.  The next at 2600 yards recorded .89 miles.  Not quite right, but again, not an issue.

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The Fuse needs to be synced via Bluetooth to the Mio app on your smartphone.   Cloud/web capability is currently in the testing phase (according to Mio).  Implementation with 3rd parties such as Garmin require business agreements and such.  This is good news, as hopefully a few months down the road (from publication of this review) there will be a way to export Fuse data.  It has a limited amount of storage, and if you don’t sync it frequently it won’t be able to record an activity.  This is no problem, syncing is fast and easy.  The app is easy to use.  You can set up your profile and customize heart rate zones, or set daily goals.  All very straightforward.  Where the app lacks currently, for me, is data analysis.  Select an activity (it asks you to confirm, you can choose from running, road biking, walking, mountain biking, climbing, swimming, rowing and hiking) and click on it.  Then you can see the stats (avg HR, time, distance, calories, most frequent zone, time, speed and pace) but for Android users, no heart rate graph.  It is shown only on the iOS app.   According to Mio they are testing this and it should be available for update for Android in the upcoming weeks (from publication of this review). A heart rate graph will be very nice to see, particularly for the swims (as there is no heart rate data field option on the Garmin 910xt, you can pair Mio to the 920xt in open water swim mode, not as a data field but it will show up in analysis on Connect). It sounds like Mio is very aware of what consumers want in terms of functionality and data analysis, and are in the process of making that happen.

All told, I am impressed with the Fuse and would recommend it to any athlete who is interested in an alternative to the chest strap, or to any active person interested in activity tracking.

Compatibility of the Mio Fuse to other devices and apps can be found on its product page. It can be purchased directly from Mio or at Amazon with the affiliate link below:
Save 20% on Mio heart rate monitor watches with promo code Mio-Bucks at checkout! Valid through 3/31/15 11:59PM

Rebecca Adamson
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Rebecca Adamson

Head Coach/Founder at KR Endurance
Coaching runners and triathletes since 2012.
Degrees/Certifications: B.A., ITCA, NESTA Sports Injury Specialist and Lifestyle Weight management specialist, US Masters Swimming certified Level 1&2 Coach

Race Experience: Boston marathon 2010, 2011, 2012; Ironman Lake Tahoe 2013 finisher; Ironman Coeur d’Alene 2014 finisher
Contact: rebecca@krendurance.com
Rebecca Adamson
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  • Meir

    Hi, is the screen visible while swimming? can you click the button to wake it up when swimming?

    • hamptonrunner

      Hi, sorry for the delay in answering – I wanted to confirm my response. The answer is yes, you can click the button to wake it when swimming. However, you also have the option to have the screen always visible when in workout mode.

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