Are built-in HRMs really a match for chest straps?

I was lucky enough to be picked as an Epson Runner, which means that over the past month or so I’ve been testing out the Epson Runsense SF-810 against my trusty Garmin Forerunner 910XT.

Garmin and Epson Heart Rate Monitors

Phew, why do sports watches have such flipping long names!?

One of the selling points of the Epson watch is the built-in HRM, which uses an integrated optical sensor to monitor your HR from your wrist. Epson claim that this is just as accurate as a chest strap. Needless to say, I was a wee bit dubious – as were the friends I mentioned it to.

The question is, can a built-in sensor really give you the same accuracy as a chest strap?

Or on the flip-side, is a chest strap really the only way to get an accurate reading?

In the name of science, I risked looking like a complete numpty with my 2 watches and tested the Epson alongside my Garmin on this week’s long run:

Garmin and Epson HRM Comparison

#techwanker alert…

By about 40 minutes into my 10 miler (i.e., the top of the first nasty hill!), the watches were around 2-3 bpm apart. There was a bit of a glitch at the beginning as the Epson decided to split the first mile into 3 laps of 0.08, 0.00 and 0.91 (no idea how that happened!)

But besides the squiffy first mile, the readings seemed fairly close between the 2 watches:

Garmin and Epson HRM Breakdown

As my handy little diagram above shows (lol…) the overall average for the Garmin measured as 159bpm, whilst the Epson showed 168bpm.

In a slightly more readable format, the HR splits were:

M2: Garmin 139, Epson 162

M3: Garmin 170, Epson 167

M4: Garmin 168, Epson 170

M5: Garmin 167, Epson 171

M6: Garmin 167, Epson 171

M7: Garmin 169, Epson 165

M8: Garmin 169, Epson 171

M9: Garmin 168, Epson 170

M10: Garmin 173, Epson 168

Whilst I found this experiment quite interesting, I’m not an expert when it comes to training by heart rate. According to various places – including Runners World – my LSRs should be in the 60-70% zone (117-136) and hills should peak at 85% (165), which means that I was way out of the target heart rate zone if either of those watches were correct.

How can I have run 10 miles in a zone that Runners World reserves for 5-10k race efforts!?

Do you use a heart rate monitor, or train to heart rate zones? Any tips?

Do I reeeally have to slow down as much as I think I do!?

– – –

Disclaimer: Whilst this isn’t a sponsored post, in exchange for leaving 5 video reviews I am allowed to keep the Runsense, which I tested without charge.

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