Cited by 140Non-Invasive Vital Sign MonitoringCardiovascular and exercise physiologyHeart Rate Variability and Autonomic Control

Accuracy of optical heart rate sensing technology in wearable fitness trackers for young and older adults: validation and comparison study

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Chow, Hsueh-Wen, Yang, Chao-Ching·2020·JMIR mHealth and uHealth

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Abstract

BACKGROUND: Wearable fitness trackers are devices that can record and enhance physical activity among users. Recently, photoplethysmography (PPG) devices that use optical heart rate sensors to detect heart rate in real time have become popular and help in monitoring and controlling exercise intensity. Although the benefits of using optical heart rate monitors have been highlighted through studies, the accuracy of the readouts these commercial devices generate has not been widely assessed for different age groups, especially for the East Asian population with Fitzpatrick skin type III or IV. OBJECTIVE: This study aimed to examine the accuracy of 2 wearable fitness trackers with PPG to monitor heart rate in real time during moderate exercise in young and older adults. METHODS: A total of 20 young adults and 20 older adults were recruited for this study. All participants were asked to undergo a series of sedentary and moderate physical activities using indoor aerobic exercise equipment. In this study, the Polar H7 chest-strapped heart rate monitor was used as the criterion measure in 2 fitness trackers, namely Xiaomi Mi Band 2 and Garmin Vivosmart HR+. The real-time, second-by-second heart rate data obtained from both devices were recorded using the broadcast heart rate mode. To critically analyze the results, multiple statistical parameters including the mean absolute percentage error (MAPE), Lin concordance correlation coefficient (CCC), intraclass correlation coefficient, the Pearson product moment correlation coefficient, and the Bland-Altman coefficient were determined to examine the performances of the devices. RESULTS: =6.04%). The scores for reliability test of CCC for Garmin were 0.92 (Young) and 0.80 (Senior), whereas those for Xiaomi were 0.76 (Young) and 0.73 (Senior). However, the results obtained using the Bland-Altman analysis indicated that both test optical devices underestimated the average heart rate. More importantly, the study documented some unexpected outlier readings reported by these devices when used on certain participants. CONCLUSIONS: The study reveals that commonly used optical heart rate sensors, such as the ones used herein, generally produce accurate heart rate readings irrespective of the age of the user. However, users should avoid relying entirely on these readings to indicate exercise intensities, as these devices have a tendency to produce erroneous, extreme readings, which might misinterpret the real-time exercise intensity. Future studies should therefore emphasize the occurrence rate of such errors, as this will likely benefit the development of improved models of heart rate sensors.

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  • Technological limitations are primarily sensor-related (LED wavelength, light intensity, placement), while algorithmic limitations stem from biased datasets, poor calibration, and underrepresentation of darker skin in training cohorts.

    “Technological limitations are primarily sensor-related - such as LED wavelength, light intensity, and placement - while algorithmic limitations stem from biased datasets, poor calibration, and underrepresentation of darker skin in training cohorts.”

    From Photoplethysmography in Diverse Skin Tones: Evaluating Bias in Smartwatch Health Monitoring (2025) · cites this paper as [27]

    The Introduction (Accuracy of Optical Heart Rate Monitoring; Research Gaps, page unavailable) identifies sensor placement and skin structure as factors in optical heart-rate accuracy. The Discussion (Limitations, page unavailable) says devices may use different PPG modules or algorithms, but the paper does not identify LED wavelength or light intensity as primary limitations, or attribute algorithmic limitations to biased training datasets, poor calibration, or underrepresentation of darker skin in training cohorts. Its observation that earlier validation studies enrolled mostly white participants concerns study samples, not algorithm training cohorts. (LLM, conf=0.86)

    Experimental — accuracy not yet measured
  • Misleading heart rate readings lead to negative consequences such as substandard recovery assessments, improper exercise intensity control, and cardiovascular condition identification, resulting in deteriorated fitness results and healthcare outcomes.

    “Misleading heart rate readings lead to several negative consequences, such as substandard recovery assessments and improper exercise intensity control, and cardiovascular condition identification, resulting in deteriorated fitness results and healthcare outcomes [27].”

    From Photoplethysmography in Diverse Skin Tones: Evaluating Bias in Smartwatch Health Monitoring (2025) · cites this paper as [27]

    Split into 2 atoms — 0 confirmed, 2 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

    Experimental — accuracy not yet measured
  • For light skin pigmentation, pulse rate mean bias was -1.24 bpm (95% CI -5.31 to 2.83).

    “Mean biases were –1.24 (95% CI –5.31 to 2.83) bpm, –0.89 (95% CI –3.70 to 1.93) bpm, and –0.57 (95% CI –9.44 to 8.29) bpm for the corresponding groups (Table 4 and Figures 5-7 [41,60-62]).”

    From Impact of skin pigmentation on pulse oximetry blood oxygenation and wearable pulse rate accuracy: systematic review and meta-analysis (2024) · cites this paper as [62]

    The Results (Reliability of Examined Devices, Table 1; page unavailable) report heart-rate mean differences by age group, activity, and device, not a light-pigmentation group. Searches for −1.24, the stated interval, and skin-pigmentation subgroup results found no passage reporting this estimate. The Introduction (Aim of the Study; page unavailable) describes a study of participants with Fitzpatrick skin types III or IV. (LLM, conf=0.77)

    Experimental — accuracy not yet measured
  • For light skin pigmentation, pulse rate 95% limits of agreement were -16.02 to 13.54 bpm.

    “Our analysis revealed 95% LoA of –16.02 to 13.54 bpm, –18.62 to 16.84 bpm, and –33.69 to 32.54 bpm for light, medium, and dark skin pigmentation groups, respectively.”

    From Impact of skin pigmentation on pulse oximetry blood oxygenation and wearable pulse rate accuracy: systematic review and meta-analysis (2024) · cites this paper as [62]

    The Methods and Results report limits of agreement by age group, activity, and device, not by light, medium, and dark skin-pigmentation groups. Searches for “−16.02 to 13.54,” “16.02,” and skin-pigmentation subgroup results found no passage reporting the claimed limits for light skin. (LLM, conf=0.78)

    Experimental — accuracy not yet measured
  • For medium skin pigmentation, pulse rate 95% limits of agreement were -18.62 to 16.84 bpm.

    “Our analysis revealed 95% LoA of –16.02 to 13.54 bpm, –18.62 to 16.84 bpm, and –33.69 to 32.54 bpm for light, medium, and dark skin pigmentation groups, respectively.”

    From Impact of skin pigmentation on pulse oximetry blood oxygenation and wearable pulse rate accuracy: systematic review and meta-analysis (2024) · cites this paper as [62]

    The Results section (Bland-Altman Analysis; page unavailable) reports limits of agreement by age group, device, and activity, not by light, medium, and dark skin pigmentation. A search for the stated limits of −18.62 to 16.84 bpm and for skin-pigmentation subgroup analyses found no passage verifying that figure. The citing sentence also describes the figures as the citing authors’ own analysis. (LLM, conf=0.72)

    Experimental — accuracy not yet measured

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Research works printed but not linked: 1

  1. [17]Shih PC Han K Poole ES Rosson MB Carroll JM Use and Adoption Challenges of Wearable Activity Trackers iConference 2015 Proceedings 2015 iConference'15 March 24-27, 2015 Newport Beach, California, USA

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Authors
Chow, H.-W., & Yang, C.-C.
Affiliations
National Cheng Kung University (TW)
Corresponding author
Chow, Hsueh-Wen
Venue
JMIR mHealth and uHealth
Published
2020-04-28
Volume
8
Issue
4
Pages
e14707
ISSN
2291-5222 (ISSN-L)
OpenAlex
W3004958388
Cited by
140
References
58
Citations by year
2026: 12 · 2025: 38 · 2024: 26 · 2023: 40 · 2022: 12 · 2021: 10 · 2020: 2
FWCI
5.02
Type
journal article
Language
en
Open access
Licence
cc-by
Locations
  • JMIR mhealth and uhealth (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
Funders
Ministry of Science and Technology, Taiwan (MOST108-2410-H006-099)
Topics
  • Physical Sciences › Engineering › Biomedical Engineering › Non-Invasive Vital Sign Monitoring
  • Health Sciences › Medicine › Complementary and alternative medicine › Cardiovascular and exercise physiology
  • Health Sciences › Medicine › Cardiology and Cardiovascular Medicine › Heart Rate Variability and Autonomic Control
Keywords
wearable activity trackers, photoplethysmography, heart rate accuracy, older adults, young adults, exercise intensity monitoring, Fitzpatrick skin type, device validation
MeSH terms
Fitness Trackers, Wearable Electronic Devices, Aged, Heart Rate, Humans, Technology, Reproducibility of Results, Optics and Photonics, Young Adult

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