Is there a difference between wrist and chest strap heart rate measurement?

Wrist heart rate measurement systems in GPS Heart Rate Monitors & Sports Watches are here to stay. And right now they are the ones that dominate the market, and have become consolidated products. Thus, the traditional chest strap is beginning to be replaced mainly for comfort, but from Runnea Pulsometers we wonder if the change is for better or worse. Is the technology sufficiently developed? How does each measurement system differs from one brand to another? These are some of the questions we ask ourselves, and to which we try to give a complete answer.

You may be interested in: The 10 best heart rate monitors without chest strap

You know that we are staunch supporters of the use of heart rate monitors in our workouts (our running training system is based on the runner's heart rate) and therefore we have spoken with product managers from Suunto and Polar to give us their assessments of this technology and its proper use ...

How does your measurement system work?

• SUUNTO : The optical pulse sensor is placed on the underside of the watch in contact with the skin of the wrist. This sensor emits an LED light that illuminates the skin and is able to detect blood flow through the skin by the way this light is scattered. The technical term for this technology is photoplethysmography (PPG) which is based on the fact that light penetrating the body will be scattered in a predictable manner based on the change in blood flow, such as heart rate (pulse) or by changes in blood flow volume.

Suunto Spartan Sport Wrist HR I Suunto Spartan Wrist Trainer HR

• POLAR: We have three systems for measuring heart rate (depending on the number of LEDs on the device and where it is located (wrist or arm), but the basis is that LEDs located on the device emit pulsed green light to the skin and thanks to a light sensor lets you know how much light has been absorbed by the bloodstream. For practical purposes, when the heart beats (a pulsation occurs) the volume of blood passing through the veins increases. As there is more blood volume, the reflected light returning to the light sensor is less which causes the sensor to detect it and identify it as a heartbeat.

Polar M600 I Polar M430 I Polar Polar M200

How is it different from the competition?

• SUUNTO : It uses an optical pulse sensor with technology from Valencell, the leading innovator in the campo of biometric technology for wearable devices. Suunto has partnered with Valencell, which is a company dedicated 100% to the development of optical sensors for heart rate monitoring. It is also one of the most recognized and advanced in this campo. Working together with a company focused in this campo allows us to offer the consumer the best technology available in the market.

The same optical pulse sensor can have different configurations for different sports and activities, so we have different configurations for Running, cycling, swimming and daily use.

• POLAR: The technology, such as the calculation algorithm of our systems, has been developed and patented by Polar. The number of LEDs differs from competing products. We are pioneers and leaders in HR-based functions so the reliability is among the highest in the market.

What variation do you estimate there is with respect to the chest strap?

• SUUNTO : The company Valencell has done an independent test where you can see the different accuracies of some sensors on the market. In the study our Spartan Sport Wrist watch had the best accuracy results in pulse sensors measured from the wrist, even better than the Valencell devices themselves. The study is very interesting, and you can see it HERE.

It influences in which area of the wrist you place it: yes, the watch has to be well adjusted, the less oscillation it has on the wrist the more accurate it will be measuring the pulse.

• POLAR :3 beats at both low and high heart rates.

How to get the best performance from an optical HR sensor?

• SUUNTO : The watch must be held directly against the skin. No clothing, no matter how thin, between your skin and the watch.

The watch has to be placed a little higher on the arm than where we usually place a conventional watch. The sensor reads the passage of blood flow through the skin. The more skin near the sensors, the better the reading.
Arm and muscle movements, such as gripping a tennis racket, can affect the accuracy of the reading.
When the pulse is low, the sensor may not be able to take a stable reading. A short warm-up before the reading may help.
For maximum accuracy and faster response times to pulse changes, we recommend using a HR chest strap, such as the Suunto Smart Sensor. The use of a HR chest strap will allow for more accurate and faster pulse readings as well as for example being able to wear the watch on the handlebars of a bicycle or wearing the watch over a garment.

Does it affect where on the wrist you wear it?

• POLAR: Yes, in the wrist recording system it should be placed on the outside of the wrist above the wrist bone. In the system for recording heart rate on the arm( OH1 sensor), the best location is on the outside of the forearm or on the upper outer arm (triceps).

Does the watch need to be worn very tightly?

• SUUNTO : The watch should be snug, but should not cut off circulation.

• POLAR : It should be tight but should not hinder blood circulation. In case you want to use it for swimming, it should be well adjusted to ensure constant contact between the sensor and the skin.

Does it affect to have a lot of hair on the wrist?

• SUUNTO : Dark pigmented skin, tattoos, body hair can block the light and allow reliable readings of the optical sensor.

• POLAR : No conclusive data on this but would advise using the 6 LED system instead of the 2 LED system to ensure a better reading.