Smartwatches Measure Heart Rate Levels: How Reliable Is It?

heart rate monitors

Heart Rate Monitor Watch

Today's smart watches can not only help us measure steps, but also help us measure heart rate and maximum oxygen uptake, giving us a deeper understanding of our health status and exercise ability. However, the data itself does not speak. These indicators What health indicators can it reflect? How can we better understand our physical condition through these data?

Heart rate

The definition of heart rate is relatively simple, that is, the number of times the heart beats per minute. In English, bpm (beats per minute) is commonly used as the unit of heart rate.

1. How does the watch obtain heart rate?

For normal people (not in atrial fibrillation), the heartbeat corresponds to the pulse, and one heartbeat corresponds to one pulse. So we can usually know the heart rate by touching the pulse at the wrist. So how are watches measured? Is it possible that there is a pressure sensor on the watch that senses the different pressures when the pulse beats to calculate the pulse?

This sentence is half correct. The watch also estimates the heart rate based on periodic pulse changes. However, the watch does not sense pressure changes, but senses blood changes through light to determine the heart rate. The professional name of this method is photoplethysmography. ,PPG). PPG is a compound word of Photo (light), Plethysmos (change), and Graphos (record). Literally, it is a measurement method that uses light to record changes in arteries passing through parts of the body.

heart monitoring watch

So, what are pulse waves? Pulse wave refers to the contraction and relaxation of the heart and the microscopic changes in blood vessels during blood circulation. PPG is a measurement that identifies these pulse waves as waveforms. Simply put, the heart alternately contracts and relaxes, the blood flow in the blood vessels repeatedly increases and decreases, and the blood composition also changes. At this time, the method of detecting reflected or transmitted light by emitting a light source to the skin is PPG.

PPG can not only measure heart rate, but also blood oxygen saturation, blood pressure, and respiratory rate. Different wavelengths are used when obtaining different PPG metrics. Because hemoglobin absorbs more red light, red light and near-infrared are mostly used when measuring blood oxygen saturation.

But on the other hand, red light is more affected by movement, so when measuring heart rate, green light is more commonly used. Green light also has shortcomings. Green light is greatly affected by sweat. Therefore, in actual practice, manufacturers often use a variety of light sources to measure heart rate, blood pressure and other parameters.

2. Is the watch accurate in measuring heart rate?

Heart rate detection is the most mature technology in PPG, and the measurement results are also relatively accurate.

Although the watch is more accurate in measuring heart rate among the general population, the heart rate measurement may be affected in some people. For example, skin color and obesity may affect the test results. The reason is that darker skin with higher melanin absorbs more light. Furthermore, the skin of obese people is often thicker, contains less moisture, and has less blood flow than the skin of non-obese people, resulting in larger PPG deviations.

3. What information can it help us understand?

Health Category

Heart rate indicators are very common and can reflect a lot of sports and health information. According to the American Heart Association, a normal adult's resting heart rate (heart rate at rest) is 60-100bpm. A resting heart rate of more than 100 beats is called tachycardia, a resting heart rate of less than 60 beats is called bradycardia, and irregular beatings are called arrhythmias.

But in fact, if your resting heart rate is greater than 80, your health risks will increase. However, a resting heart rate less than 60 does not necessarily pose a health risk, and may also be a sign of training adaptation. People who exercise regularly may have a resting heart rate lower than 60 bpm because their heart muscles are stronger and can pump more blood with each heartbeat, so they can meet the blood circulation throughout the body with a lower heart rate. For example, the resting heart rate of some elite swimmers can be as low as 38 beats, which can be said to be a veritable "big heart."

SpO2 monitor watch


Heart rate not only reflects health status, but is also often used to reflect exercise intensity. The more intense the exercise, the faster the heartbeat. In turn, we can quantify our exercise intensity based on our current heart rate. As the intensity of exercise increases, the heart rate will not increase infinitely, but will have a maximum value. Generally, we will determine the intensity of exercise by calculating the ratio of the heart rate during exercise and the maximum heart rate.

Determining exercise intensity is crucial for scientific and efficient exercise. After being able to judge the intensity of exercise, we can prescribe exercise and carry out exercise in a more targeted manner. People often wonder which form of exercise can help lose weight. For example, can jumping rope help lose weight? Can running and dancing help you lose weight? In fact, whether you can lose weight has nothing to do with the form of exercise. It is mainly related to the intensity and duration of exercise. The body doesnÔÇÖt know if we are dancing or running, it only recognizes intensity. As long as you exercise at a moderate intensity and have enough time, you can lose fat.

Why medium intensity? The calories stored in fat are very large, but the decomposition rate is very slow. When the exercise intensity is relatively high, the energy supply from fat cannot keep up with the body's needs. At this time, carbohydrates are mainly used for rapid energy supply, so the exercise intensity cannot be too high; when the exercise intensity is When you are relatively young, although fat is the main energy supply substance, for example, fat accounts for 70% of the energy supply at rest. However, the total energy consumption is relatively small at this time. Even if the energy supply ratio of fat is large, the calories consumed are still small, and the purpose of fat loss cannot be achieved.

Therefore, if you want to lose fat, it is more recommended to engage in moderate-intensity exercise. Without a watch, we need to touch the pulse to obtain the heart rate, and cannot understand the heart rate in time. The emergence of smart watches has solved this problem very well and can help us measure heart rate and evaluate exercise intensity.


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