In episode 6 of the Art and Science or Running, Coaches Malc Kent and Jacob Puzey discuss the pros and cons of training and racing by heart rate.
Malc explains the two fundamental ways to measure heart rate:
The classical mode – with a chest strap has two key parts or electrodes on the back of the device to pick up an electrical signal of the heart pumping. In theory, it’s a very simple algorithm of how many peaks were measured in one minute (BPM). However, the simple algorithm depends on the person’s heart. Not all hearts are created equal. Algorithms can be refined to better isolate peak signal of the heart, but that requires knowledge of how the algorithms work.
One tip for improving signal pickup with a classical heart rate chest strap is to wet the sensors with saliva or water prior to adhering to the body.
Since 2013 there are now optical wrist heart rate sensors which measure different colours of oxygenated blood. This way of measuring heart rate sends out light which in turn is disturbed by a wave of energy in the blood vessel of oxygenated blood. However, this means of measurement is still not as accurate as the traditional electrocardio (chest strap) method.
We often hear from our athletes that their optical heart rate data is either off by 5-10 beats per minute or goes in and out in the first few mi/kms of a run. This means that athletes need to be prepared to mentally clean up data when they review it after a run and not rely too heavily upon it during the run.
One additional problem with optical heart rate accuracy is that it doesn’t work as effectively with darker tones of skin or tattooed skin. For more details about this, please read Fitbits and other wearables may not accurately track heart rates in people of color.
* Read more about the Firstbeat technology contained in most major watches at
All in a heartbeat: How Firstbeat became the secret sauce in your fitness wearable – The company trying to turn your heart rate into personal feedback
Trail and ultrarunning coach and author, David Roche discusses some of these challenges in his article: Why You Should Be Skeptical About Your Wrist-Based Heart Rate: Wrist-based heart-rate technology is not perfected yet, and it varies based on the watch and athlete.
Malc, who has worked with some of the major players in the watch and wearable technology space, explains that major watch company use published academic papers to formulate algorithms as a means of avoiding liability and litigation:
“When you see something on a watch, that isn’t you specifically. That is a very very simplistic model or algorithm that originated with some studies that didn’t take into extremes from around the world so you have to take it all with a pinch of salt.” – Malc Kent
Most of these studies are very small populations of runners in controlled conditions.
These studies are based on the generally accepted equation that Max Heart Rate = 220 BOM – Age
Both Jacob and Malc explain that they are both outliers for most algorithms. Malc has a small heart and therefore a very high heart rate which means his lactate threshold is also high. Jacob in contrast has a very high VO2 Max, but his lactate threshold is relatively low compared to his VO2 Max.
Jacob shares examples of other outliers in the sport who also happen to be engineers and understand their unique datasets and use their o...