How Accurate Are Smartwatches for Tracking Your Workouts?
Share
Introduction
Smartwatches are everywhere—from tracking your steps to monitoring your heart rate and calories burned. But how reliable are these numbers? A new study looked at three popular wrist-worn devices—the Apple Watch 6, Polar Vantage V, and Fitbit Sense—to find out how accurate they really are at measuring heart rate and energy burned during exercise.
Why Accuracy Matters
For many people, wearables are not just about motivation—they're tools used to plan workouts, set goals, or even track progress in a weight loss journey. For athletes, coaches, and healthcare professionals, having accurate heart rate and energy data is important when designing training programs or dietary plans.
That’s why knowing which device you can trust—and when—is so important.
What the Study Did
Researchers tested 60 healthy young adults using the three devices during five types of activity:
- Sitting
- Walking
- Running
- Resistance training
- Cycling
The goal was to see how well each device measured heart rate and energy expenditure (calories burned), compared to professional-grade lab equipment.
Heart Rate: Apple Leads the Pack
The good news? All three devices were fairly accurate in tracking heart rate, especially during higher-intensity workouts.
- Apple Watch 6 was the most accurate across all five activities. Its readings were within 3 beats per minute of the lab equipment in most cases.
- Polar Vantage V came second, with strong accuracy in sitting, running, and strength training.
- Fitbit Sense was decent, especially during running and cycling, but had more variation during low-intensity activities like sitting.
So, if heart rate monitoring is your main concern, especially across a range of activities, the Apple Watch 6 is currently your best bet.
Calories Burned? Not So Trustworthy
When it comes to tracking calories burned, the picture isn’t as rosy.
- All three devices significantly over- or under-estimated energy expenditure, depending on the activity.
- Errors were as high as 25–30%, and even the best-performing device (Apple Watch 6) showed considerable inconsistency.
This means if you’re relying on your smartwatch to tell you how many calories you burned during a workout—especially for managing diet or weight—it might be leading you astray.
Why Are Calorie Counts So Off?
Estimating energy expenditure is complicated. These devices use a mix of heart rate, movement, and personal data (like weight, age, and sex) to calculate how many calories you burn. But without directly measuring your breathing and oxygen use (like lab equipment does), these are really just best guesses—and they can be way off, especially for activities like weightlifting or cycling.
What This Means for You
If you use a smartwatch:
- Trust the heart rate data, especially during cardio activities like running or cycling.
- Be skeptical of calorie burn estimates—use them for rough comparison only.
- Don’t base your diet or workout intensity only on what your watch tells you.
- Focus more on long-term trends than exact numbers.
Final Thoughts
Smartwatches are amazing tools that can help keep you motivated and on track. But they aren’t perfect—especially when it comes to calorie counting. If you're using your wearable for health or fitness goals, it’s best to understand its strengths and limitations.
In short: use your watch to guide your fitness, not to define it.