Heart rate monitor, radio pulse or optics?
The heart rate is an important parameter to keep an eye on during physical trainings as it gives information about the sessions’ intensity and the possible physiological adjustments that can be made.
Nowadays, the heart rate monitors’ market offers two ways of measurement: using optics or radio pulse. In this article we will explain the pros and cons of each solution.
radio pulse and chest strap.
It used to be the reference in the physical training fields before the arrival of optics. They work by recording the heart’s electrical activity thanks to a group of electrodes strapped on the chest.
The main advantages are the measure’s accuracy and precision, which have been demonstrated and proven by comparison with other instruments such as the electrocardiogram, obtaining results with no significant differences.
Moreover, the price-quality ratio plays to its favour: as the technology ages the prices continue to drop.
One disadvantage of this solution is the chest strap itself which can obviously be annoying during exercises, and in certain cases, such as for swimmers, slightly inhibit performance.
heart rate monitors using optics.
This technology is based on the fact that blood is red, because it reflects red rays and absorbs green ones. Optical sensors, associated with green LED and photosensitive diodes, can detect the amount of blood going through the wrist at a precise moment.
When the heart is beating, the arterial flow in the wrist is more intense and the absorption of the green lights increases as well. By making the LED shine hundreds of times per minute, it is possible to calculate the number of heart beats per minute, therefore the heart rate.
The main advantage here is the comfort, as wearing a bracelet will suffice. More and more versions are released on the market with different kinds of new features, some of them being waterproof for example.
Concerning the downsides, even in perfect conditions the pulse measurement may not be entirely reliable. Moreover, certain factors can affect the heart rate sensor performances and prevent its reading: the thickness of the skin or the amount of blood running which can differ from one person to another may interfere with the sensors’ sensitivity. Other issues may arise from low temperatures in which case the measurement’s accuracy is considerably reduced. Finally, rhythmic movements such as running can degrade the reading as well.