Modern wearable devices show improved heart rate and step count accuracy compared to older modelsModern wearable devices show better accuracy for heart rate tracking

Frontiers in Medicine Published August 22, 2026 Study authors: Tristan Hogue, Alexia Khoury, Pressila Njeim, Nicole Aswad, Layale Youssef, Sarah Birtulescu, Andréa… DOI ↗ Editorial oversight: Dr. Amelia Tan, PhD · Internal Medicine & Chronic Disease

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Key Takeaway

Note that while modern wearables show improved heart rate and step counts, energy expenditure accuracy remains limited.

This systematic review synthesized data from 47 studies to evaluate the performance of wrist-worn consumer and research-grade devices compared to established reference standards like ECG and indirect calorimetry. The analysis focused on heart rate accuracy, energy expenditure, step counts, and physical activity intensity classification.

Findings indicate significant technological improvements over time. Modern heart-rate monitors typically achieve validity scores above 0.80 during exercise, whereas pre-2010 models showed correlations as low as 0.50. Similarly, current step-count accuracy for steady-state walking is below 5%, a marked improvement from errors of up to 25% in models prior to 2017. Activity intensity misclassification also improved from over 20% in early models to 10%-15% in current multi-sensor devices.

Despite these improvements, energy expenditure accuracy remains limited, with recent devices showing a 10%-40% error relative to indirect calorimetry. The authors note that this limitation is due to the lack of direct oxygen and carbon dioxide measurements. While user acceptability for these devices is generally high across brands, clinicians should note that variability across different brands and specific activities persists.

If you use a fitness tracker to monitor your health, you might wonder how much of that data is actually correct. A review of 47 studies shows that technology has improved significantly over the last decade. While older heart rate monitors often failed to meet accuracy standards during exercise, modern devices now consistently reach high validity scores.

However, not every metric has caught up. While step counting has become very accurate for steady walking, measuring how much energy you burn remains tricky. Because these devices cannot measure oxygen and carbon dioxide directly, there is still a 10% to 40% error rate when estimating calories burned.

Overall, people find these devices easy and comfortable to wear every day. While some differences between brands still exist, the jump in heart rate accuracy shows that modern wearable tech is becoming much more reliable for tracking your physical activity.

What this means for you:

Modern wearables are now very accurate at tracking heart rates, but calorie counting remains less precise.

Common questions

Are modern heart rate monitors accurate during exercise?

Yes, modern wrist-worn devices typically achieve validity scores above 0.80 during exercise. This is a significant improvement over older models from before 2010, which often fell below the standard of 0.90.

How accurate are these devices at counting steps?

Step counting has improved greatly. While older devices had errors up to 25%, current technology shows less than a 5% error rate for steady-state walking.

Can I rely on my watch to track calories burned?

Accuracy for energy expenditure is still limited. Because these devices cannot measure oxygen and carbon dioxide directly, there is currently a 10% to 40% error rate when estimating how many calories you burn.

Study Details

Study typeMeta analysis

EvidenceLevel 1

PublishedAug 2026

View Original Abstract ↓

Wrist-worn physical activity trackers have advanced rapidly over the past two decades, evolving from simple accelerometer-based devices to multi-sensor systems integrating photoplethysmography, advanced movement classification, and machine-learning algorithms. Despite widespread use in both research and clinical settings, concerns remain regarding the accuracy and reliability of key metrics such as heart rate, energy expenditure, step count, and activity intensity. This systematic review followed PRISMA guidelines (PROSPERO: CRD42024551740). MEDLINE, Scopus, PubMed, and SPORTDiscus were searched for studies evaluating the accuracy or acceptability of wrist-worn activity trackers in laboratory or free-living-simulated conditions. Eligible studies included healthy or general-population samples using any wrist-worn consumer or research-grade device. Reference standards included ECG, indirect calorimetry, doubly labelled water, manual step counting, and research-grade accelerometry. Of 1,659 records identified, 47 studies met inclusion criteria. Accuracy improved substantially over time, although variability across brands, activities, and populations persisted. Early heart-rate monitors (pre-2010) frequently reported Pearson correlation coefficient as low as 0.50 during exercise, while still being under the validity standard (0.90) at rest. Modern devices such as Apple Watch and Garmin vivosmart demonstrate markedly increased validity scores (typically above 0.80 during exercise), reflecting improvements in optical sensor quality and motion-artifact filtering. Energy-expenditure accuracy showed the least improvement; even recent devices exhibit 10%–40% error relative to indirect calorimetry, reflecting the inherent challenge of estimating metabolic rate without direct O₂ and CO₂ measurement. Step-count accuracy, prior to 2017 showed errors of up to 25%, now commonly falls below 5% for steady-state walking due to improved accelerometer precision and gait-pattern recognition. Classification of physical-activity intensity has also improved, with misclassification decreasing from >20% in early models to 10%–15% in current multi-sensor devices. Acceptability was generally high across brands, with long wearing time and good participant satisfaction.

Modern wearable devices show improved heart rate and step count accuracy compared to older modelsModern wearable devices show better accuracy for heart rate tracking

Common questions

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Modern wearable devices show improved heart rate and step count accuracy compared to older modelsModern wearable devices show better accuracy for heart rate tracking

Common questions

Study Details

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