Heart rate watch as precise as ECG

Tom Tom Runner Cardio watch has heart rate monitor as accurate as hospital reading

Tom Tom Cardio Watch

Heart rate watch as precise as ECG

I’m extremely suspicious of running gadgetry. Temperamental, obstructive, too basic, too garish – I’m very fussy about how I track my runs. And sometimes I prefer not to track them at all.

So when TomTom, the makers of in-car navigation systems, launched a GPS watch for runners, I raise an eyebrow. Cars are not people – how can a car company get to grips with the intricacy of the running mind and all it demands? A GPS Sport Watch must be unobtrusive but robust, stylish but modest, wide-ranging but precise. It must do more than get you from A to B.

And Tom Tom’s Runner Cardio watch and its built-in heart rate monitor has an even harder audience to crack – women. Women despise the typical heart rate straps that irritate the chest and constantly fall off even when hooked into a special sports bra.

But, begrudgingly, I am fairly impressed with this heart rate monitor. There is one sole reason: it’s as accurate as an electrocardiogram reading – a hospital test that measures the electrical activity of the heart.

Now, there were a lot of other things to recommend this watch. Tom Tom strapped one onto my wrist, as tight as possible without cutting off the blood supply, and sent me on a magical mystery tour of zombie mazes, bowling alleys and even a quick spin with Olympic cyclist Victoria Pendleton to test my heart rate in different zones.

But it was the medical doctor, hauled up on stage after Vicky P had been on the mike, and his confirmation that this watch is as entirely accurate as an ECG, that was all I needed to start thinking that I might incorporate it into my runs. Of course, it is not an ECG and won’t detect abnormalities of the heart; it is just as accurate as one. But for me, haunted by my first age-old pedometer that didn’t record steps properly to another top-of the-range sports watch that lost GPS on long runs, accuracy has always been everything, otherwise what’s the point?

How to run to the beat

This can seem fiddly to calculate but bear with, it’s actually quite simple. The aim is to find two things

Your maximum heart rate (the highest possible HR you can achieve

Your working heart rate (the difference between your max and resting HR) that you will use to find your training zone (more on that later)

1. Calculate your maximum heart rate

For women, calculate 209 – (0.9 x age)

**This can be wrong by up to 25 beats so you can find a more accurate max HR by doing the following test on a treadmill

  • Sprint as fast as you can for 2 mins
  • Jog gently for 2 mins
  • Repeat a fast sprint for 3 mins – this is your max HR.


Now choose which zone you want to train in.

60-70% – easy

75%-85% – medium

85%-95% – hard

Each zone is based on your working HR, not your maximum HR.

So, if you want to train at 90%, for example, you must do the following calculation:

  1. Multiply your working HR (max HR minus resting HR) by the zone percentage you want to train at. For example, 150 x 0.90 = 135
  2. Finally, add this figure to your resting HR e.g. 90 + 56 = 146bpm – this is what you are aiming for to train at 90%

Why is HR training useful?

Many runners dismiss HR training as they believe they can tell when they are pushing themselves to the max. They are also usually the preserve of elite, and so more pernickety runners. However, HR monitors are good for:

  • Checking that you’re sustaining the heart rate and not letting yourself off just because it’s the end of the workout.
  • When you fatigue, your legs might feel like stone and you feel like you’re slowing down, but your HR may still be going like the clappers. This can be motivating.
  • A useful tool for fartlek and interval sessions to ensure each rep is consistent.


Chris Macdonald

Written by Chris Macdonald | 348 articles | View profile

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