How accurate are heart rate monitors in fitness watches?

@giles.heathcote 

Heart rate monitors in fitness watches can generally be quite accurate. However, their accuracy depends on various factors such as the quality and design of the watch, the placement of the sensors, and the individual's characteristics.

Optical heart rate monitors, which use light to measure heart rate, are commonly found in fitness watches. These sensors work by detecting the blood flow through the wrist. While they can provide reasonably accurate heart rate readings during moderate-intensity activities, they may be less accurate at higher heart rates or during activities with significant arm movement.

Factors like sweating, tattoos, or darker skin tones may also have an impact on accuracy. These variables can interfere with the sensors' ability to detect blood flow reliably, potentially leading to inaccurate readings.

For individuals requiring highly accurate heart rate measurements, such as professional athletes or those with specific medical conditions, chest strap heart rate monitors are typically considered more precise. These monitors use electrodes to directly measure electrical signals from the heart.

Overall, while fitness watch heart rate monitors can provide a good estimate of heart rate during everyday activities, they may not be as accurate as medical-grade devices like EKG machines or chest strap monitors in certain situations.

@giles.heathcote 

Additionally, it's important to note that heart rate monitors in fitness watches are not designed for medical purposes and should not be used as a substitute for medical advice or evaluation. They are intended to provide individuals with a general idea of their heart rate during exercise and overall fitness tracking.

If you have concerns about the accuracy of your heart rate monitor, it's always a good idea to compare its readings with other methods, such as manually taking your pulse or consulting with a healthcare professional.