How Do Fitness Smartwatches Track Activity?

22 minutes read

Fitness smartwatches track activity using a combination of sensors and algorithms designed to monitor various physical parameters. At the core of this technology is an accelerometer, which detects motion and orientation, allowing the device to count steps, estimate the distance traveled, and determine when the user is active. Many smartwatches also include gyroscopes to measure rotation and enhance the accuracy of movement tracking. Heart rate monitors, often based on optical sensors, measure the pulse rate by shining light through the skin and analyzing blood flow. Some advanced models incorporate GPS for precise tracking of outdoor activities like running or cycling, providing data on speed and route. Barometers may also be present to detect changes in elevation, useful for tracking activities such as hiking or climbing stairs. These sensors work together with sophisticated algorithms to differentiate between types of activity, calculate calories burned, and assess overall fitness levels. The data collected is often synced with mobile apps or cloud services, allowing users to track progress over time, set goals, and adjust their fitness routines accordingly.

Best Fitness Smartwatches of March 2025

1
Fitbit Versa 4 Fitness Smartwatch with Daily Readiness, GPS, 24/7 Heart Rate, 40+ Exercise Modes, Sleep Tracking and more, Waterfall Blue/Platinum, One Size (S & L Bands Included)

Rating is 5 out of 5

Fitbit Versa 4 Fitness Smartwatch with Daily Readiness, GPS, 24/7 Heart Rate, 40+ Exercise Modes, Sleep Tracking and more, Waterfall Blue/Platinum, One Size (S & L Bands Included)

  • Get inspired and stay accountable with Versa 4 + Premium - learn when to work out or recover, see real-time stats during exercise and find new ways to keep your routine fresh and fun.Operating temperature: -14° to 113°F. Radio transceiver: Bluetooth 5.0.Maximum operating altitude : 28,000 feet (8,534 m).
  • Built for better fitness results: Daily Readiness Score(1), built-in GPS and workout intensity map, Active Zone Minutes, all-day activity tracking and 24/7 heart rate, 40+ exercise modes and automatic exercise tracking, water resistant to 50 meters
  • Tools to measure and improve sleep quality: personalized Sleep Profile(1), daily sleep stages & Sleep Score, smart wake alarm and do not disturb mode. Compatibility-Apple iOS 15 or higher, Android OS 9 or higher
  • Maintain a healthy body and mind: daily Stress Management Score, reflection logging, SpO2(2), health metrics dashboard(3), guided breathing sessions, menstrual health tracking and mindfulness content
2
Garmin vívoactive 5, Health and Fitness GPS Smartwatch, AMOLED Display, Up to 11 Days of Battery, Black

Rating is 4.9 out of 5

Garmin vívoactive 5, Health and Fitness GPS Smartwatch, AMOLED Display, Up to 11 Days of Battery, Black

  • Designed with a bright, colorful AMOLED display, get a more complete picture of your health, thanks to battery life of up to 11 days in smartwatch mode
  • Body Battery energy monitoring helps you understand when you’re charged up or need to rest, with even more personalized insights based on sleep, naps, stress levels, workouts and more (data presented is intended to be a close estimation of metrics tracked)
  • Get a sleep score and personalized sleep coaching for how much sleep you need — and get tips on how to improve plus key metrics such as HRV status to better understand your health (data presented is intended to be a close estimation of metrics tracked)
  • Find new ways to keep your body moving with more than 30 built-in indoor and GPS sports apps, including walking, running, cycling, HIIT, swimming, golf and more
  • Automatic nap detection and nap logging tracks your nap length during the day, providing personalized insights on how it affects your Body Battery energy monitoring and more (data presented is intended to be a close estimation of metrics tracked)
3
Smart Watch(Answer/Make Call), 2025 New Smartwatch for Men Women, 1.96" HD Fitness Watch with 110+ Sport Modes, Heart Rate, Sleep Monitor, Pedometer, IP68 Waterproof Activity Tracker for Android iOS

Rating is 4.8 out of 5

Smart Watch(Answer/Make Call), 2025 New Smartwatch for Men Women, 1.96" HD Fitness Watch with 110+ Sport Modes, Heart Rate, Sleep Monitor, Pedometer, IP68 Waterproof Activity Tracker for Android iOS

  • 2025 New Smart Watch with Bluetooth Call/Intelligent Notifications: The smart watches for men adopts bluetooth 5.3 version for a faster and more stable connection. With a built-in premium microphone and hd speaker, allowing you to answer calls and interact with voice assistants directly from smartwatch. Meanwhile, you can receive message notifications and read them from your watch, such as Facebook, Messenger, Instagram, Gmail, Whatsapp, Twitter etc. Just raise your wrist to view messages.
  • 1.96" HD Big Screen and Unlimited Customization Dials: smart watches for women adopt 1.96”TFT HD color display screen (320*386 resolution) which making it easy to operate and sensitive, experience crystal-clear visuals like never before. 4 level brightness adjustable allows you to read time and data clearly even under the glare. 200+ Multiple trendsetting combinations to match your mood and outfit of the day. Even create and customize your own mens smart watch faces from your phone gallery.
  • 24/7 Heart Rate Monitor and Sleep Tracker: Adopted high-performance optical sensors, Fitness tracker provides health monitoring features such as 24-hour continuity real-time Heart Rate, SpO2, and Sleep Monitoring(Deep/light sleep). It accurately monitors your heart rate in real time nd better understand your heart rate trends. Also, it provides a detailed analysis of your sleep quality and facilitating lifestyle adjustments by "GloryFit" continuously recording your sleep patterns.
  • All Day Activity and Practical Functions: During exercise, sport smart watch automatically records daily steps, distance counter,calories burned, active minutes. This fitness watch men has other useful features offered like remote camera, music control, weather forecast, sedentary reminder, GPS tracking, stopwatch, find phone, raise to wake, alarm clock, calculator, etc. It makes things on your wrist simple and easy, and will always work as your effective daily assissant.
4
Smart Watch, 1.85" HD Smartwatch for Men Women (Answer/Make Calls), Fitness Watch with Heart Rate/Sleep/IP68 Waterproof/120+ Sports Modes/Spo2 Monitor, Pedometer, Android Smart Watch for Android iOS

Rating is 4.7 out of 5

Smart Watch, 1.85" HD Smartwatch for Men Women (Answer/Make Calls), Fitness Watch with Heart Rate/Sleep/IP68 Waterproof/120+ Sports Modes/Spo2 Monitor, Pedometer, Android Smart Watch for Android iOS

  • Bluetooth Call and Voice Assistant: Smart watch built-in microphone and HD speaker, you can make and receive calls directly from this smart watches for men. You can also use the built-in voice assistant to ask questions, control music playback and more
  • 1.85'' HD Screen and DIY Dials: Android smart watch features a TFT HD color screen and curved 3D curved glass for superior picture quality and touch sensitivity. You can also choose from 100+ dials or personalize the dial with your favorite photos
  • 24 Hour Health Monitoring: The built-in sensor of the smart watches for women has been upgraded, which is faster and more powerful in monitoring heart rate, blood oxygen and sleep, and provides a comprehensive sleep quality analysis (non-medical standard)
  • 120+ Sports Modes: Active Fitness Tracker monitors over 120 activities including walking, running, cycling, swimming, yoga and more. Receive real-time stats directly on your wrist and record your stats in the "Da Fit" app
5
Smart Watch Health Fitness Tracker with 24/7 Heart Rate, Blood Oxygen Blood Pressure Sleep Monitor, 115 Sports Modes, Step Calorie Counter Pedometer IP68 Waterproof for Android and iPhone Women Men

Rating is 4.6 out of 5

Smart Watch Health Fitness Tracker with 24/7 Heart Rate, Blood Oxygen Blood Pressure Sleep Monitor, 115 Sports Modes, Step Calorie Counter Pedometer IP68 Waterproof for Android and iPhone Women Men

  • 【Health Metrics Monitoring】These fitness watches for women and men pack 24/7 heart rate, blood oxygen, blood pressure monitors and sleep tracker. You could check those real-time health metrics anytime, anywhere conveniently on your wrist and check the all-day data record in the App.The sleep tracker keeps track of time spent in different sleep stages including REM, light sleep,deep sleep,and the time when you wake up, helps you to get a better understanding of your sleep quality.
  • 【115 sports modes & All-Day Activity Tracking】There are more than 115 sports modes tracking available in the activity trackers and smartwatches, covering almost all daily sports activities you can imagine, gives you new ways to train and advanced metrics for more information about your workout performance.The all-day activity tracking feature monitors your steps, distance, and calories burned all the day, so you can see how much progress you've made towards your fitness goals.
  • 【Notifications for Calls and Messages】Getting notifications for incoming calls and texts right away from your wrist while on the go, allowing you to stay connected with family and friends with calls, texts, and email, so you never miss an important call or message. You could see the caller's name, reject the call, mute the ring-tone, and read the whole text messages directly from the smart watch for android phones and iphone.
  • 【A Considerate Life Assistant】The fitness trackers for women and men provide you with more features including drinking water reminder, sedentary reminder,menstrual cycle reminder, real-time weather display, remote camera shooting, music control,timer,and do-not-disturb mode, making it a considerate life assistant.With the GPS connectivity, you could get a map of your workout route in the app for outdoor activity by connecting to your phone GPS.
6
Jacoosa Smart Watch, 1.85" HD Smartwatches for Men Women, 100 Days Standby Time, 110+ Sport Modes with Fitness Tracker Watch, IP68 Waterproof, Heart Rate/Sleep Monitor, Fitness Watch for Android/iOS

Rating is 4.5 out of 5

Jacoosa Smart Watch, 1.85" HD Smartwatches for Men Women, 100 Days Standby Time, 110+ Sport Modes with Fitness Tracker Watch, IP68 Waterproof, Heart Rate/Sleep Monitor, Fitness Watch for Android/iOS

  • Bluetooth Call and Smart Notifications:Smart watches for men allows you to stay in touch with your family or friends anytime, anywhere, even when you're at the gym, outdoors, or doing other activities. You can also receive social media, Facebook, WhatsApp, and text message alerts on your wrist, so you'll never miss an important message or notification
  • 1.85 Inch HD Screen and DIY Dials: Smart watch features a TFT HD color screen for superior picture quality and touch sensitivity. Men's watches have more than 100 unique online dials to choose from, and you can also customize your dial. It can be any photo, such as family, pets, etc
  • 30 Days Standby Time and Multiple Features: Smartwatch has a built-in 1000 mAh high-capacity battery that ensures up to 8-14 days of use, and about 30 days of standby time with just 2 hours of charging. The sports watch also includes weather forecast, music control, camera control, alarm, stopwatch, find phone and many other useful features. Simply download “FitCloudPro” for free from the App Store or Google Play and enjoy your smart life
  • 110+ Fitness Modes and IP68 Waterproof: The fitness tracker watch offers up to 110+ exercise modes covering running, cycling, fitness and other activities to meet different users' preferences. During exercise, it records real-time data such as heart rate, steps, calories burned, distance and activity time. This men's smartwatch is IP68 waterproof and can be worn during outdoor activities, rainy days and hand washing (Note: Please do not use it in shower, sauna, swimming, etc.)
7
Smart Watch(Answer/Make Call), 1.91" Smartwatch for Men Women, NEW Fitness Watch with 110+ Sport Modes, Fitness Activity Tracke with Pedometer/Sleep Monitor/Heart Rate/IP68 Waterproof, for Android iOS

Rating is 4.4 out of 5

Smart Watch(Answer/Make Call), 1.91" Smartwatch for Men Women, NEW Fitness Watch with 110+ Sport Modes, Fitness Activity Tracke with Pedometer/Sleep Monitor/Heart Rate/IP68 Waterproof, for Android iOS

  • Bluetooth Call and Message Reminder: The mens smart watch are equipped with the latest Bluetooth 5.3 chip, which increases the connection speed by 80%, and a highly stable connection with no delay. Answer and make calls right from your wrist, and easily sync multiple mobile contacts. It also supports multiple smart reminders, including incoming calls, Email, texts, SMS messages (Facebook, WhatsApp, Twitter, Tiktok, Instagram, Gmail etc). You won't miss any important calls or notifications.
  • 1.91" HD Big Screen and DIY Dials: Fitness tracker features a TFT HD color screen (320 * 380 touch screen)and curved 3D curved glass for superior picture quality and touch sensitivity. Watch for men have more than 100+ unique online watch faces to choose from, you can also customize your watch face. It can be any photo, such as your family, star, pets, etc. Meanwhile, 4 levels manually adjust the brightness, so you can clearly see the displayed time and exercise data even in direct sunlight.
  • 24-Hour Health Activity Tracker: Smart watches for women track your Heart Rate, Blood Oxygen levels(SpO2) and Sleep patterns around the clock(deep sleep, light sleep, sleep quality analysis). And Your can track your period with menstrual cycle tracking and ovulation prediction as well. All data is presented in the "GloryFit" app, offering a comprehensive view of your health status. Watches women it is compatible with Android 5.0 and higher and iOS 9.0 and higher.


How do fitness devices motivate users through gamification?

Fitness devices use gamification to motivate users by incorporating elements that make tracking and improving fitness levels engaging and enjoyable. Here are several ways they accomplish this:

  1. Achievements and Badges: Users earn achievements or badges when they reach specific milestones, such as completing a certain number of steps, workouts, or active minutes. These provide a sense of accomplishment and encourage users to set and achieve goals.
  2. Challenges and Competitions: Many fitness devices allow users to participate in challenges, either with themselves or with friends. These challenges can be based on daily step counts, workout sessions, or specific fitness goals. Adding a competitive element often motivates users to stay active.
  3. Leaderboards: Users can see how they stack up against others, whether in a group of friends or within the larger community of device owners. This stimulates a competitive spirit and can motivate users to improve their rankings.
  4. Progress Tracking: Visual representations of progress, such as graphs or fitness streaks, help users see their improvements over time. This visual feedback reinforces positive behavior and encourages continued effort.
  5. Quests and Missions: Some devices introduce themed quests or missions, where users must complete certain activities to proceed or "unlock" the next level. This adds a narrative element to the fitness journey, keeping it engaging and entertaining.
  6. Virtual Rewards: Apart from badges, some apps provide virtual rewards, like unlocking new functionalities or customizing avatars, as users achieve their fitness goals.
  7. Social Sharing and Community: The ability to share achievements and progress on social media or within a fitness community creates a sense of belonging and accountability, which can drive motivation by providing positive reinforcement from peers.
  8. Feedback and Notifications: Regularly updated feedback, reminders, or nudges (like vibrating alerts for inactivity) keep users engaged and mindful of their fitness goals.
  9. Personalization: Tailoring the gamified elements to the individual’s personal goals, preferences, and fitness levels ensures that the challenges are both achievable and motivating.


Overall, by integrating these gamification strategies, fitness devices transform exercise from something that might be perceived as a chore into an interactive and rewarding experience.


How do fitness trackers recognize different workouts?

Fitness trackers use a combination of sensors and algorithms to recognize different workouts. Here are some of the key technologies and methods they utilize:

  1. Accelerometers: These sensors measure acceleration forces in different directions. By analyzing patterns in these data, the device can detect specific types of movement associated with different exercises, such as running, cycling, or walking.
  2. Gyroscopes: Often used in conjunction with accelerometers, gyroscopes measure orientation and angular velocity. This helps improve the accuracy of motion tracking and can be essential in distinguishing between exercises that involve complex, multi-directional movements.
  3. Heart Rate Monitors: Heart rate data can help identify workout intensity and sometimes the type of workout. More intense activities like running and cycling typically result in higher heart rates compared to lighter exercises like walking or yoga.
  4. Machine Learning Algorithms: Fitness trackers use algorithms that have been trained on large datasets of movement patterns associated with various exercises. Over time, these algorithms can improve in accuracy, learning to better distinguish between similar activities.
  5. GPS: For outdoor activities, GPS data is used to track movement across distances. This is particularly useful for identifying and distinguishing between activities such as running, cycling, and hiking.
  6. Altimeters: These measure changes in elevation and can be used to track activities involving altitude changes, such as hiking or climbing stairs.
  7. Environmental Sensors: Some devices can also utilize barometers, thermometers, and other sensors to gain context about environmental conditions, which might influence workout type recognition.


These sensors and technologies are integrated into the fitness tracker, and their data is processed in real-time. While they can often accurately identify many common exercises, some activities might still require manual input or confirmation from the user for precise tracking.


What is SpO2 monitoring in smartwatches?

SpO2 monitoring in smartwatches refers to the measurement of blood oxygen saturation levels using sensors embedded in the device. SpO2 stands for peripheral capillary oxygen saturation, which is an estimate of the amount of oxygen in the blood. It is expressed as a percentage – for example, a normal SpO2 level typically ranges from 95% to 100%.


Smartwatches achieve this by using optical sensors, often located on the back of the watch, which emit and detect light waves passing through the skin. These sensors typically use a combination of red and infrared light to measure the amount of oxygenated and deoxygenated hemoglobin in the blood. By analyzing the way light is absorbed and reflected by the blood vessels, the smartwatch can estimate the user's blood oxygen level.


Monitoring SpO2 is useful for assessing certain aspects of a person's health and fitness. It can be particularly beneficial for tracking respiratory conditions, understanding the effects of altitude on the body, and improving athletic performance by ensuring muscles are getting sufficient oxygen during workouts. Additionally, during sleep, SpO2 monitoring can provide insights into sleep quality and detect issues like sleep apnea. However, it's important to note that while smartwatch SpO2 sensors can provide useful data, they are not a substitute for professional medical equipment and diagnosis.


How do fitness smartwatches track sleep patterns?

Fitness smartwatches track sleep patterns using a combination of sensors and algorithms. Here’s a breakdown of how they typically work:

  1. Accelerometer: Most fitness watches have a built-in accelerometer, which is a sensor that detects motion. By measuring your movements, the watch can infer how restless you are during sleep and help classify different sleep stages (light, deep, and REM sleep).
  2. Heart Rate Monitor: Many smartwatches are equipped with an optical heart rate monitor. By observing changes in your heart rate, the watch can estimate transitions in your sleep cycles, considering that heart rate tends to vary between different sleep stages.
  3. Heart Rate Variability (HRV): Some advanced models analyze HRV, which refers to the variation in time between each heartbeat. HRV can provide additional insights into sleep stages and overall sleep quality.
  4. Gyroscope: This sensor aids in detecting orientation and rotation, which enhances motion tracking accuracy, further contributing to the classification of sleep stages.
  5. Blood Oxygen Monitor (SpO2 sensor): Some smartwatches measure blood oxygen levels. Variations in oxygen levels can indicate sleep apnea or other breathing disturbances, offering a more comprehensive view of sleep health.
  6. Skin Temperature Sensors: Changes in skin temperature throughout the night may provide additional data points for algorithms to improve sleep detection accuracy.
  7. Machine Learning Algorithms: Sophisticated algorithms are used to synthesize data from these various sensors to provide insights into your sleep patterns. These algorithms are often trained on large datasets to recognize patterns and improve accuracy over time.
  8. User Input: Many devices use user-provided information, such as typical sleep and wake times, to help improve the accuracy of sleep tracking.


After collecting data throughout the night, fitness smartwatches will synthesize this information and often present it in an app, giving you detailed insights into your sleep duration, efficiency, sleep stages, and overall sleep quality. Keep in mind that while these devices can provide helpful insights, they may not be as accurate as polysomnography tests conducted in sleep laboratories.


How do fitness smartwatches measure heart rate?

Fitness smartwatches typically measure heart rate using optical heart rate sensors, which employ a technology called photoplethysmography (PPG). Here's how it generally works:

  1. LEDs: The smartwatch is equipped with light-emitting diodes (LEDs), usually green because this wavelength is absorbed well by blood, providing a strong signal.
  2. Light Penetration: These LEDs shine light onto the skin, usually on the wrist. The light penetrates the skin and illuminates the underlying blood vessels.
  3. Light Absorption and Reflection: As blood pumps through the vessels, it absorbs the light differently at different times due to the changing volume of blood, which correlates with the heartbeat.
  4. Photodetector: A photodetector in the smartwatch measures the amount of light that's either reflected back to the sensor or transmitted. By analyzing how the light's reflection changes over time, the smartwatch can determine your heart rate.
  5. Data Processing: The data from the sensor is processed by algorithms in the smartwatch or connected app to calculate the heart rate in beats per minute (BPM).


This method is generally effective but can be prone to inaccuracies under certain conditions, such as when there's excessive movement, loose fitting, or ambient lighting conditions that interfere with the sensor. Some smartwatches also use additional technologies, such as electrocardiogram (ECG) sensors, for more accurate heart measurements, though these are less common and typically found in advanced models.

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