ECG or PPG? What are they and which is better?

2 min read
Wednesday, 24 August 2022

Heart rate monitoring has progressed hugely in the past several years, with both ECG and PPG sensors being used in more wearables.

One of the biggest questions asked when considering a heart rate monitor is "what’s the difference between ECG and PPG?", quickly followed by "Which is the most accurate?"

Read on to find out the answer to both of these questions.

Measuring your heart rate

Understanding the speed at which your heart beats is important throughout any physical activity. This is what is being measured, for both ECG and PPG, when using a fitness tracker or heart rate monitors.

Electrocardiography (ECG)

This is considered the gold standard for measuring heart rate. Every time your heart beats, the heart muscle depolarises and this sends a tiny electrical wave towards the skin. It’s these electrical signals that are picked up by an ECG sensor on the skin's surface.

Photoplethysmography (PPG)

PPG is the most commonly used measurement of heart rate for heart rate trackers. As your heart beats, the volume of blood changes within your cardiovascular systems, including the small skin vessels such as your veins and arteries. It is this change in volume which is recorded by the PPG sensor, via a small LED light.

These trackers shine a that small LED light through the skin and record how much of the light is absorbed and sent back. The difference in amount of light absorbed is dependent upon blood volume level, so higher volumes of blood in the vessels means more light is absorbed and when lower volumes, less light.

So, which is best? ECG or PPG?

ECG is considered the gold standard due to it measuring the actual heart activity. However, due to the need for it to be measured close to the heart it can be more difficult measure to obtain. Whereas, PPG indirectly measures heart rate and so can, theoretically, be measured anywhere with adequate access to skin vessels.

Although not as accurate as ECG, it is worth noting that PPG is still an incredibly accurate measure of heart rate.

Does my Myzone use ECG or PPG sensors?

Can't decide which sensor is best for you? The good news is that the MZ-Switch features both ECG and PPG sensors depending on where you wear it for your physical activity.

At 99.4% accuracy when worn on the chest, the ECG sensor on the Switch's chest strap (as with the MZ-3) is ideal for anyone looking for the most accurate heart rate monitoring.

When worn on the arm or wrist, the Switch's PPG sensor will give you 95% accuracy. Not only that, but you can also record activity in water, too.

For more details, read more about the MZ-Switch.

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