Key result
Apple Watch accurately measures HR and steps but exceeds ~10% validity thresholds for energy expenditure.
Why the study?
Findings on Apple Watch accuracy vary across conditions, and few previous reviews have used a meta-analytic approach to quantitatively evaluate its accuracy in measuring health metrics.
Does the Apple Watch accurately measure energy expenditure, heart rate, and step counts in adults compared to reference measures?
Meta-Analysis
Does the Apple Watch accurately measure energy expenditure, heart rate, and step counts in adults compared to reference measures?
The Apple Watch provides generally accurate heart rate and step measurements, but its accuracy for energy expenditure is limited and exceeds the 10% validity threshold.
Answers are grounded in this paper and cite their sources.
Clinicians should avoid relying on Apple Watch energy expenditure estimates; confirms accuracy for heart rate and steps but leaves validation gaps open.
Objective . Wearable technology like the Apple Watch is increasingly important for monitoring health metrics. Accurate measurement is crucial, as inaccuracies can impact health outcomes. Despite extensive research, findings on the Apple Watch’s accuracy vary across different conditions. While previous reviews have summarized findings, few have utilized a meta-analytic approach. This study aims to quantitatively evaluate the accuracy of the Apple Watch in measuring health metrics. The accuracy of the Apple Watch was assessed in measuring energy expenditure (EE), heart rate (HR), and step counts (steps). Approach . We searched Embase, PubMed, Scopus, and SPORTDiscus for studies on adults using the Apple Watch compared to reference measures. The Bland–Altman framework was applied to assess mean bias and limits of agreement (LoA), with robust variance estimation to address within-study correlations. Heterogeneity was assessed across variables such as age, health status, device series, activity intensity, and activity type. Additionally, the mean absolute percentage error (MAPE) reported in the included studies was summarized by subgroups. Main results . This review included 56 studies, comprising 270 effect sizes on EE (71), HR (148), and steps (51). The meta-analysis showed a mean bias of 0.30 (LoA: −2.09–2.69) for EE (kcal min −1 ), −0.12 (LoA: −11.06–10.81) for HR (beats min −1 ), −1.83 (LoA: −9.08–5.41) for steps (steps min −1 ). The forest plots showed variability in LoA across subgroups. For MAPE, all subgroups for EE exceeded the 10% validity threshold, while none of the subgroups for HR exceeded this threshold. For steps, some subgroups exceeded 10%, highlighting variability in accuracy based on different conditions. Significance . This study demonstrates that while the Apple Watch generally provides accurate HR and step measurements, its accuracy for EE is limited. Although HR and step measurements showed acceptable accuracy, variability was observed across different user characteristics and measurement conditions. These findings highlight the importance of considering such factors when evaluating validity.
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Choe et al. (2025) conducted a meta-analysis in Health metrics monitoring. Apple Watch vs. Reference measures was evaluated on Accuracy in measuring energy expenditure (EE), heart rate (HR), and step counts (Mean bias: EE 0.30, HR -0.12, steps -1.83, 95% CI LoA: EE -2.09 to 2.69, HR -11.06 to 10.81, steps -9.08 to 5.41). The Apple Watch provides accurate heart rate and step measurements, but its accuracy for energy expenditure is limited, with all EE subgroups exceeding the 10% validity threshold.
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