Fitness trackers are one of the most common devices worn today. At the same time, digital health offers solutions for most things—that is, they claim to monitor your physical activity, sleep patterns, and general welfare.
As these gadgets continue to gain popularity, so do questions about the accuracy and reliability of the data returned by the devices. Are fitness trackers precision tools, they claim, or high-tech guesswork?
How Fitness Trackers Work
The backbone of most activity trackers involves a combination of sensors recording movement data for a wearer and physiological responses. This includes:
• Accelerometers: These sensors detect motion in multiple directions, allowing the tracker to count steps, measure distance travelled, and estimate calories burned.
• Optical heart rate monitors: They transmit the light into the skin, which detects blood flow changes that determine your heart rate through a PPG technique.
• Altimeters: Some trackers have altimeters that allow the device to measure elevation changes, thus abilities such as stair climbing or hill hiking.
While the underlying technology is impressive, it varies significantly depending on placement on the body, type of activity, and individual physiology with a high degree of accuracy.
Step Counting: A Step in the Right Direction?
Maybe one of the most basic functions associated with a fitness tracker is that of counting steps. How accurate are those counts, however? Several studies have shown that under controlled circumstances, such as walking on a treadmill, most trackers are precise reasonably, typically remaining within 5 percent of the correct count. This goes out of the window during real-world use, especially for irregular arm movements like pushing a stroller or supermarket cart.
It’s also worth noting that multiple trackers can pick up a different number of steps, even when worn simultaneously.
This is because every manufacturing company applies individual and proprietary algorithms upon raw data from the sensors. While step count is helpful in setting total activity levels, they should not be regarded as highly accurate readings but rather rough approximate measurements.
Heart Rate Monitoring: Getting to the Heart of the Matter
Heart rate must be quantified not only to track the intensity of exercise but also as an indicator of cardiovascular health. Currently, in most commercial fitness trackers, an optical heart rate monitoring system is dominant and has improved tremendously in recent years. Generally, these sensors demonstrate reasonable accuracy for jogging or steady-state cycling with average errors against chest strap monitors or, more significantly, ECGs usually remaining within ± a few beats per minute.
High-intensity interval training and activities involving rapid movement of the arms are conditions under which the accuracy may be reduced since the sensors could potentially mistake motion artifacts for heartbeats. Some activity trackers have added extra sensors, such as ECGs and pulse oximeters, to enhance the accuracy. Still, then again, such technologies are relatively novel and might need further validation.
Calorie Counting: The Burning Questions
Probably, one of the most debatable topics connected with modern fitness trackers is their capability to estimate calorie burn. While devices can approximately calculate the expenditure of energy by heartbeat, steps, and users’ demographics, it has been shown that these can be off by as much as 30-50%.
The issue is that there are many variables involved in the process of calorie burn, which range from a complex interplay between body composition, metabolism, and exercise efficiency to even easier variations from one individual to another. Thus, tracker-based calorie estimates should be treated only as rough approximations rather than firm measurements. One may, therefore need additional tools, such as food diaries or gas exchange testing measuring metabolic rates in terms of different degrees of exertion, to get at least a rough tracking of both intake and expenditure of calories.
Sleep Tracking: Counting Sheep
Most activity trackers provide sleep tracking as one of their capabilities. The activity trackers can estimate the amount and quality of snooze time through a combination of motion sensors, confounded with heart rate monitoring. Essentially, graphing overall sleep trending, because these activity trackers methodologically follow less intensive techniques than conducted clinical sleep studies—like electroencephalography, recording electrical activity of the brain—they are not as accurate.
It’s tough for trackers to differentiate between light sleep and wakefulness, and most of them cannot detect specific sleep stages, like REM or deep sleep. They can still be helpful tools for catching possible sleep problems and motivating better sleep hygiene.
How to Use Your Fitness Tracker Properly
Despite all the limitations of activity monitors, they can be good motivators if appropriately applied. Here are some tips to get the most from your tracker:
- Focus on trends, not absolutes: Rather than getting worked up over any data point in general, look for the patterns and trends over time. Are you gradually increasing your daily step counts? Is your resting heart rate slowly trending down? Those are the types of insights that can help you track progress and stay motivated.
- Use a VPN: While your tracker synchronizes the data into mobile apps or online platforms, preferably use a virtual private network that will protect personal data and secure it. This is especially important when working on public Wi-Fi networks or sharing sensitive health information. You can go for Surfshark, ExpressVPn, or NordVPN as they are reliable services.
- Integrate tracking with other tools: Generally, fitness trackers are only one tool—albeit an important one—in the process of maintaining health and wellness. Combine tracker data with food diaries, workout logs, and regular checkups with your healthcare provider for best results.
- Listen to your body: While trackers make available precious objective data, it is not good to become out of touch with the subjective experience. If you are tired, sore, or do not feel well, do not discount those signals because a tracker says you should keep pushing.
