Measuring the pulse on Xiaomi Watch S1 Active: the complete guide

Modern wearables have evolved from simple pedometers to powerful health monitoring tools, and the Xiaomi Watch S1 Active is a vivid representative of this evolution. Device owners often wonder how to make the most of the built-in optical sensor for monitoring heart rate in real time. Understanding the principles of the sensor allows not only to track the physical shape, but also to detect abnormalities in the cardiovascular system.

The accuracy of readings depends on the correct fit of the gadget on the wrist and understanding the settings of the software part of the MIUI for Watch shell. If the device sits too loose or, conversely, is drawn, algorithms can give out incorrect data, which is especially critical during intense sports loads. In this article, we will discuss in detail all aspects of monitoring heart rate, from basic settings to analyzing complex recovery metrics.

And it's worth noting that the optical sensor on the back of the case uses LED light technology to detect the volume of blood in the capillaries, a complex biometric system that requires calibration and certain operating conditions to produce verifiable results. Let's look at how to make your gadget work at maximum efficiency.

The principle of operation of the sensor and the correct landing of the device

The monitoring system in the Xiaomi Watch S1 Active is based on an optical heart rate sensor, which uses photoplethysmography to emit light of a certain wavelength, which is absorbed by hemoglobin in the blood, and analyzes the reflected signal. To work properly, light rays must penetrate the skin and return to the sensor, which dictates strict requirements for the density of the body to the wrist.

Many users make the mistake of wearing the watch too loosely, like a regular piece of jewelry, which creates microgaps between the sensor and the skin, where ambient light enters, creating noise for the sensor. Proper fitting implies that the watch should fit tightly, but not compressively, to the skin, eliminating any displacement of the body when active hand movements.

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To achieve maximum accuracy during exercise, tighten the strap one click tighter than in normal wear mode, but be careful not to disrupt blood circulation.

The sensor should be located about 1-2 centimeters above the wrist bone, where the skin is thinner and blood flow is closer to the surface. If you wear the watch too close to the hand or, conversely, too high to the elbow, the accuracy of measurements can be significantly reduced due to the anatomical nature of the vascular arrangement.

⚠️ Attention: Tattoos, scars or thick hair on the wrist can block the light of the sensor, making measurements impossible or extremely inaccurate.

Setting up the monitoring frequency in the Mi Fitness app

Biometric tracking is managed through the linked Mi Fitness mobile app (formerly known as Zepp Life for some models, but the S1 Active works with Mi Fitness). This is where the user can flexibly adjust the frequency of automatic measurements to find a balance between data accuracy and device autonomy. Standard settings are often too conservative for athletes.

To change the parameters, you need to go to the device profile and select the section responsible for monitoring health, and you can find different intervals, from the economical mode, which takes measurements rarely, to the high-precision mode, which captures changes every minute or more often, and the choice of mode depends on your current goals — whether it is just a general observation or preparation for a marathon.

It's important to understand that turning on continuous monitoring significantly increases battery consumption. The device's algorithms run in the background, constantly polling the sensor and processing data. Unless you plan on doing a deep analysis of your daily rhythms, it's wise to set a 10 or 30 minute interval, which will save energy for other functions.

• 🔹 Smart mode: the device itself determines the periods of activity and makes it more frequent to measure when you move.
• 🔹 Fixed interval: measurements are made strictly at a user-defined time (1, 10, 30 minutes).
• 🔹 Shutdown: Automatic monitoring is disabled, pulse is measured only manually on request.

You can also activate the notifications that your resting heart rate is exceeded, which is useful for people with cardiovascular disease because it allows you to respond to tachycardia or other abnormalities in time, even if you don't look at your watch all the time.

Manual measurement and sports training regimes

The fastest way to get up-to-date heart data is by manually measuring it through the Quick Access menu. On the Xiaomi Watch S1 Active, you can do this by calling the feature menu and selecting the appropriate icon. The process takes about 30 seconds for the device to calibrate the signal and produce an average value.

However, the most complete data is collected in a sports training mode, where any exercise, whether running, cycling or yoga, is automatically switched to high-frequency monitoring, in which the interval between measurements is reduced to a minimum, allowing you to plot the detailed changes in heart rate throughout the activity.

During exercise, the screen displays your current heart rate, which helps monitor your workout intensity, and uses color or numerical values to tell you whether you are in a fat burning, aerobic exercise, or anaerobic threshold, which is critical for an effective and safe training process.

In addition, in some modes, the function of warning about going beyond the target zone is available: if your heart rate becomes too high for the type of activity chosen, the clock vibrates and shows a notification, recommending slowing down, which helps prevent overload of the heart and optimize recovery.

Data analysis: pulse zones and recovery

The data is only truly valuable when analyzed. The Mi Fitness app automatically distributes your training time across five major intensity zones based on your personal metrics (age, weight, maximum heart rate), and understanding these areas allows you to train consciously, not randomly.

One of the key metrics for assessing fitness is the rate of recovery of heart rate after exercise. Xiaomi Watch S1 Active is able to track how quickly your heart rate returns to normal after stopping exercise. The faster this process occurs, the better your cardiovascular system is trained.

For advanced users, VO2 Max (maximum oxygen consumption) is available based on pulse and pace data, which is considered the “gold standard” in the assessment of cariorespiratory fitness. Regular monitoring of VO2 Max dynamics allows you to objectively assess the progress of training for months.

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Regular analysis of the pulse zones helps to avoid overtraining and makes each minute of training effective for achieving specific goals.

Additional functions: stress and variability

In addition to the frequency of contractions, current algorithms can measure the body's stress levels, a function based on heart rate variability (HRV), which is the change in the time intervals between beats, high variability usually indicates good recovery and low stress, while low variability can signal fatigue or nervous tension.

The Xiaomi Watch S1 Active periodically measures stress in the background if this feature is activated in the settings. Results are displayed as a scale from 0 to 100, where smaller values correspond to a relaxed state. At high stress levels, the watch can offer short breathing exercises to normalize the condition.

⚠️ Attention: Stress and HRV are indicative and cannot be used for medical diagnosis.

Also worth mentioning is the function of measuring blood oxygen (SpO2), which often works in conjunction with a pulsemeter. Although this is a separate parameter, its correlation with heart rate gives a more complete picture of the state of the body, especially when exercising in highlands or in respiratory diseases.

Troubleshooting and sensor calibration

If you notice that the watch shows unrealistic values, such as sudden jumps to 200 beats per minute at rest or, conversely, the lack of signal when active movement, you need to conduct a diagnosis. The first step should always be to clean the back of the device of contaminants, fat and sweat that can shield the sensor.

A common cause of errors is the "tattoo effect" or wearing an accessory over clothing. Make sure the sensor is in direct contact with the skin. If the problem persists, try rebooting the device, which often solves software failures in the data collection modules.

As a last resort, you can reset your monitoring settings or update your watch firmware through an app. Manufacturers often release patches that improve sensor algorithms and fix bugs associated with use cases. Verification of software is a must-have stage of troubleshooting.

Frequently Asked Questions (FAQ)