Chest Strap versus Strapless
We’ve been getting a lot of questions regarding the accuracy of the new breed of OFF THE WRIST strapless heart rate monitor devices. Products like the Mio Fuse, Garmin Vivosmart HR, Fitbit Charge HR and Polar A360. We thought we’d do our own little test ride while on a day trip out to North Wales. Please note … this test was far from PERFECT. My Edge unit had AUTO-PAUSE enabled so it stopped recording each time I stopped (and I did get lost at one point). This is just ONE comparison. I plan to do a few more over the coming weeks using Polar A360 on one wrist, Garmin Vivosmart HR on the other …..
Links to other HR accuracy tests.
Test 3 > Polar M200 (wrist based) versus Polar M450 with Polar H7 chest strap
Test Equipment Used
- Garmin Edge 800
- BlueLeza Heart Rate sensor (chest strap style – Bluetooth and ANT+)
- Garmin Vivosmart HR with Garmin Elevate off the wrist sensor (strapless)
A circular route was selected around the base of Moel Famau (North Wales) as it has some good undulation and a whopping climb out of Ruthin back to Mold. This testing route would induce a full range of heart rates from the low 100’s to my near max of approx 180.
Elevation and Speed during the test ride
To get a feel for the route and the occasions when you’d expect to see the highest heart rate effort, I have included the Elevation graph and also the Speed graph below. What we want to see is the higher heart rate correspond with the periods of climbing and high speed effort on the flats.
The Resulting Heart Rate Graphs
The graph above is from the Garmin Edge acquiring it’s heart rate from the chest strap sensor. There were NO TIMES during the ride when I believed the displayed heart rate was not representative of my perceived effort.
The graph above has been acquired directly from my wrist using the Garmin Elevate HR sensors built-in to the Garmin Vivosmart HR. There were several occasions during the ride when I believe the displayed heart rate was NOT representative of my perceived effort. Sometimes this erroneous reading would persist for several minutes – eg. displaying just 90bpm while I was climbing a 12% gradient hill pushing at approx 80% effort (should have been more like 150bpm)
General Observations and comments
The period around 2:20:00 on the graph above, where it drops to approx 90bpm, was when I was flying down the hill in to Mold. Trust me, I was pedalling as hard as I could in top gear, pushing at approximately 90% effort. I think the high speed vibration was causing this erratic reading. The Garmin Edge chest strap readings were more representative around 155 – 160 bpm. That was the time when it was at it’s worst, with the heavy vibration at speed. The start of the ride was also a bit spurious? I had two distinct climbs in the first 15 minutes as shown in the Elevation Graph at the top of the page. The strapless heart rate sensors of the Vivosmart seemed to have missed these early efforts. There was also an extended period of approximately 10 minutes when it floated around 60 to 80 bpm, again, this is erroneous and not an accurate representation of the effort.
Conclusions from this HR sensor test
During the ride I made dozens of comparisons of the heart rate shown between the two devices. The Garmin Edge acquiring it’s heart rate from the BlueLeza chest strap always reflected what I would have expected my heart rate to be (I’ve been using HRM since 1999 and I pretty well know within 4 or 5 bpm what I expect to see on the devices). The Vivosmart HR did not always match the Edge HR readings…. I would stick my finger in the air and say that for 95% of the time the strapless Vivosmart HR was 95% accurate. In my opinion, for the average recreational exerciser this is more than adequate.
Is there a future for Chest Strap style Heart Rate Sensors?
Yes … is the simple answer. But mainly for the more serious exerciser. The two main reason why the more technically minded athlete should continue to use a chest strap style HRM sensor are:
- They are MORE accurate. That’s a fact. The Garmin, Mio, Epson, Polar etc strapless HR sensors are a great convenience, but they are a way off 100% accuracy
- The HRM chest straps look at the whole ECG heart rate echo. This means they have a bucket load of physiological metrics that can be analysed by software like Elite HRV to give heart rate variability feedback and tell you when you need to step UP your training and when you really need to consider taking a rest or going for a recovery run/ride.