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Cited by 242Physical Activity and HealthContext-Aware Activity Recognition SystemsMobile Health and mHealth Applications

Estimating Accuracy at Exercise Intensities: A Comparative Study of Self-Monitoring Heart Rate and Physical Activity Wearable Devices

Open access
Dooley, Erin E, Golaszewski, Natalie M, Bartholomew, John B·2017·JMIR mHealth and uHealth
DOI 10.2196/mhealth.7043PMC PMC5374271
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Abstract

BACKGROUND: Physical activity tracking wearable devices have emerged as an increasingly popular method for consumers to assess their daily activity and calories expended. However, whether these wearable devices are valid at different levels of exercise intensity is unknown. OBJECTIVE: The objective of this study was to examine heart rate (HR) and energy expenditure (EE) validity of 3 popular wrist-worn activity monitors at different exercise intensities. METHODS: A total of 62 participants (females: 58%, 36/62; nonwhite: 47% [13/62 Hispanic, 8/62 Asian, 7/62 black/ African American, 1/62 other]) wore the Apple Watch, Fitbit Charge HR, and Garmin Forerunner 225. Validity was assessed using 2 criterion devices: HR chest strap and a metabolic cart. Participants completed a 10-minute seated baseline assessment; separate 4-minute stages of light-, moderate-, and vigorous-intensity treadmill exercises; and a 10-minute seated recovery period. Data from devices were compared with each criterion via two-way repeated-measures analysis of variance and Bland-Altman analysis. Differences are expressed in mean absolute percentage error (MAPE). RESULTS: For the Apple Watch, HR MAPE was between 1.14% and 6.70%. HR was not significantly different at the start (P=.78), during baseline (P=.76), or vigorous intensity (P=.84); lower HR readings were measured during light intensity (P=.03), moderate intensity (P=.001), and recovery (P=.004). EE MAPE was between 14.07% and 210.84%. The device measured higher EE at all stages (P<.01). For the Fitbit device, the HR MAPE was between 2.38% and 16.99%. HR was not significantly different at the start (P=.67) or during moderate intensity (P=.34); lower HR readings were measured during baseline, vigorous intensity, and recovery (P<.001) and higher HR during light intensity (P<.001). EE MAPE was between 16.85% and 84.98%. The device measured higher EE at baseline (P=.003), light intensity (P<.001), and moderate intensity (P=.001). EE was not significantly different at vigorous (P=.70) or recovery (P=.10). For Garmin Forerunner 225, HR MAPE was between 7.87% and 24.38%. HR was not significantly different at vigorous intensity (P=.35). The device measured higher HR readings at start, baseline, light intensity, moderate intensity (P<.001), and recovery (P=.04). EE MAPE was between 30.77% and 155.05%. The device measured higher EE at all stages (P<.001). CONCLUSIONS: This study provides one of the first validation assessments for the Fitbit Charge HR, Apple Watch, and Garmin Forerunner 225. An advantage and novel approach of the study is the examination of HR and EE at specific physical activity intensities. Establishing validity of wearable devices is of particular interest as these devices are being used in weight loss interventions and could impact findings. Future research should investigate why differences between exercise intensities and the devices exist.

AI snapshot

Written from the paper’s full text.

TL;DR

This study compared Apple Watch, Fitbit Charge HR, and Garmin Forerunner 225 against criterion heart rate and energy expenditure measures across sedentary, light, moderate, vigorous, and recovery stages. Apple Watch was most accurate for heart rate, but all devices showed substantial and intensity-specific errors, especially for energy expenditure.

Key findings

  • Heart rate MAPE was lowest for Apple Watch (1.14%-6.70%), followed by Fitbit Charge HR (2.38%-16.99%) and Garmin Forerunner 225 (7.87%-24.38%). Apple Watch was not significantly different from the Polar criterion at start, baseline, or vigorous intensity, but measured lower heart rate during light, moderate, and recovery; Fitbit was not different at start or moderate intensity, measured lower during baseline, vigorous, and recovery, and higher during light; Garmin was not different only during vigorous intensity and measured higher at all other stages.
  • Energy expenditure MAPE was 16.85%-84.98% for Fitbit Charge HR, 14.07%-210.84% for Apple Watch, and 30.77%-155.05% for Garmin Forerunner 225. Apple Watch and Garmin measured significantly higher EE at all stages, while Fitbit measured higher EE at baseline, light, and moderate intensity but was not significantly different at vigorous or recovery, though Bland-Altman analysis showed overestimation bias.
  • Correlations with the criterion were strongest for Apple Watch for heart rate (r=.59-.99) and EE (r=.59-.87), followed by Fitbit Charge HR (HR r=.16-.99; EE r=.42-.66) and Garmin Forerunner 225 (HR r=.05-.75; EE r=.18-.73).
  • Apple Watch EE overestimation showed significant sex and BMI interactions at baseline and recovery, with larger effects for males than females and for overweight/obese categories in some comparisons.

Methods

  • A total of 62 participants (36 females; 47% nonwhite; age 18-38, mean 22.6 years; BMI mean 24.6 kg/m²) wore Apple Watch, Fitbit Charge HR, and Garmin Forerunner 225 simultaneously, with device side/unit randomized.
  • Participants completed a 10-minute seated baseline, 4-minute treadmill stages at 2.5 mph (light), 3.5 mph (moderate), and 5.5 mph (vigorous), and a 10-minute seated recovery. Heart rate criterion was Polar T31 chest strap; EE criterion was Parvo Medics TrueOne 2400 metabolic cart.
  • Analyses included mean absolute percentage error (MAPE), Pearson correlations, repeated-measures ANOVA, Bland-Altman analysis, two-factor ANOVA for sex/BMI/age, paired-samples t tests, Mauchly’s tests with Greenhouse-Geisser correction when violated, and Cohen’s d.

Limitations

  • The paper states the laboratory setting may not generalize to free-living activities, though it was a necessary controlled first validation step; it also notes Garmin’s heart rate variability made field testing probably unnecessary for that device, while field testing Apple Watch and Fitbit Charge HR for heart rate is reasonable.
  • The paper states Apple Watch EE was tracked under the Workout app’s “indoor run” setting for all stages, which may explain higher EE at baseline and recovery, and that total calories rather than active calories were used. It also states Garmin Forerunner 225 is a GPS running watch whose EE algorithm may be based solely on running, potentially overestimating baseline and recovery, though little to no distance was recorded during sedentary activities.
  • The paper states devices are constantly updated, but changes are often aesthetic with similar error rates across studies; evident from the text, the sample was young university students drawn from kinesiology and health courses, limiting generalizability to broader populations.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.2196/mhealth.7043

Cites

29 of 29 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

0 of 55 cited sources checked · 0 supported · 0 flagged

  • Findingown data

    There was no proportional bias found in Bland-Altman analyses for Apple Watch.

    “There was no proportional bias found in Bland-Altman analyses.”
    Quote in the paperNot a substantial claim
  • Findingown data

    Fitbit Charge HR measured significantly lower heart rate during baseline (P<.001, d=0.15).

    “Fitbit Charge HR measured significantly lower heart rate during baseline (P<.001, d=0.15), vigorous intensity (P<.001, d=0.31), and recovery (P<.001, d=0.13).”
    Quote in the paperNot a substantial claim
  • Findingown data

    Apple Watch measured significantly lower heart rate readings during recovery (P=.004, d=0.03).

    “Apple Watch measured significantly lower heart rate readings during light intensity (P=.03, d=0.25), moderate intensity (P<.001, d=0.35), and recovery (P=.004, d=0.03).”
    Quote in the paperNot a substantial claim
  • Findingown data

    For Apple Watch, heart rate MAPE was between 1.14% and 6.70%.

    “For the Apple Watch, HR MAPE was between 1.14% and 6.70%.”
    • Also stated in: § Heart Rate Overview · plain
      “The magnitude of errors across all stages was least for the Apple Watch (1.14%-6.70%), followed by the Fitbit Charge HR (2.38%-16.99%) and the Garmin Forerunner 225 (7.87%-24.38%).”
    Quote in the paperSubstantial claim
  • Findingown data

    All repeated-measures ANOVA omnibus F tests were significant at the .05 level.

    “All repeated-measures ANOVA omnibus F tests were significant at the .05 level; therefore, only pairwise comparisons between device (Apple Watch, Fitbit Charge HR, and Garmin Forerunner 225) and criterion measure (Polar heart rate monitor) are reported.”
    • Also stated in: § Energy Expenditure Overview · plain
      “All repeated-measures ANOVA omnibus F tests were significant at the .05 level; therefore, only pairwise comparisons between device (Apple Watch, Fitbit Charge HR, and Garmin Forerunner 225) and criterion measure (Parvo Medics TrueOne 2400) are reported.”
    Quote in the paperSubstantial claim
  • May combine two claims. 24
  • The quote only partly states this claim. 1
  • Classified as probably not a substantial claim. 36

  • May combine two claims.

    Findingown data

    Across exercise stages, the correlation between Polar heart rate monitor criterion scores and device heart rate readings was strongest for Apple Watch (r=.59-.99), followed by Fitbit Charge HR (r=.16-.99), and weakest for Garmin Forerunner 225 (r=.05-.75).

    “The correlations between the criterion scores from the Polar heart rate monitor and the readings from the devices indicate the strongest association with Apple Watch (r=.59-.99), followed by the Fitbit Charge HR (r=.16-.99), and finally Garmin Forerunner 225 (r=.05-.75).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Across all stages, heart rate MAPE was least for Apple Watch, followed by Fitbit Charge HR, and greatest for Garmin Forerunner 225.

    “The magnitude of errors across all stages was least for the Apple Watch (1.14%-6.70%), followed by the Fitbit Charge HR (2.38%-16.99%) and the Garmin Forerunner 225 (7.87%-24.38%).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The Apple Watch provided the most accurate measure of heart rate relative to the criterion Polar heart rate monitor, as MAPE was between 1.14% and 6.70% for all stages.

    “The Apple Watch provided the most accurate measure of heart rate relative to the criterion Polar heart rate monitor, as MAPE was between 1.14% and 6.70% for all stages.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The Parvo Medics TrueOne 2400 metabolic cart and Polar heart rate monitor are valid criterion measures.

  • May combine two claims.

    Findingown data

    Across exercise stages, the correlation between Parvo Medics TrueOne 2400 criterion scores and device energy expenditure readings was strongest for Apple Watch (r=.59-.87), followed by Fitbit Charge HR (r=.42-.66), and weakest for Garmin Forerunner 225 (r=.18-.73).

    “The correlations between the criterion scores from Parvo Medics TrueOne 2400 and the readings from the devices indicate the strongest association with Apple Watch (r=.59-.87), followed by the Fitbit Charge HR (r=.42-.66), and finally Garmin Forerunner 225 (r=.18-.73).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The Garmin Forerunner 225 was the least accurate of the wearable devices, with MAPE between 7.87% and 24.38% for heart rate.

    “The Garmin Forerunner 225 was the least accurate of the wearable devices, with MAPE between 7.87% and 24.38%.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The Parvo Medics TrueOne 2400 metabolic cart and Polar heart rate monitor are valid criterion measures.

  • May combine two claims.

    Findingown data

    The magnitude of errors across all stages was least for the Fitbit Charge HR (16.85%-84.98%), followed by the Apple Watch (14.07%-210.84%), and the Garmin Forerunner 225 (30.77%-155.05%).

    “The magnitude of errors across all stages was least for the Fitbit Charge HR (16.85%-84.98%), followed by the Apple Watch (14.07%-210.84%), and the Garmin Forerunner 225 (30.77%-155.05%).”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The Parvo Medics TrueOne 2400 metabolic cart and Polar heart rate monitor are valid criterion measures.

  • May combine two claims.

    Findingown data

    Paired-samples t test determined that overweight and obese BMI categories were significantly different from the criterion for Apple Watch during moderate intensity; however, normal weight was not significantly different (P=.96).

    “Paired-samples t test determined that overweight and obese BMI categories were significantly different from the criterion; however, normal weight was not significantly different (P=.96).”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The Parvo Medics TrueOne 2400 metabolic cart and Polar heart rate monitor are valid criterion measures.

  • The quote only partly states this claim.

    Findingown data

    The two-factor ANOVA also revealed a significant interaction for BMI and device for the Apple Watch during recovery, F3,49=8.01, P<.001.

    “The two-factor ANOVA also revealed a significant interaction for BMI and device for the Apple Watch, F3,49=8.01, P<.001; paired-samples t test indicated that all BMI categories were significantly different from the criterion.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Wearable-based behavioral change interventions are becoming more prevalent.

    “With the increase in popularity, wearable-based behavioral change interventions are becoming more prevalent [4-7].”
    Quote in the paperNot a substantial claim0 of 4 sources checked
    • cites [4] source

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    • cites [6] source

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    • cites [7] source

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  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Another study examining heart rate error during treadmill activities found the highest percentage error in light walking and the least error in running for Mio Alpha, Fitbit Charge HR, Basis Peak, Microsoft Band, and TomTom devices.

    “Conversely, another study examining heart rate error during treadmill activities found the highest percentage error in light walking and the least error in running for Mio Alpha, Fitbit Charge HR, Basis Peak, Microsoft Band, and TomTom devices [19].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [19] source

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  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductnone given

    Mauchly's tests were used to test the assumption of sphericity; when violated, degrees of freedom were corrected using Greenhouse-Geisser estimates.

    “Mauchly’s tests were used to test the assumption of sphericity. When violated, degrees of freedom were corrected using Greenhouse-Geisser estimates.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S4 (based).

    Premisenone given

    Little research exists regarding whether these wearable devices, particularly those that measure heart rate, are reliable and valid for these purposes.

    “However, little research exists regarding whether these wearable devices—particularly those that measure heart rate—are reliable and valid for these purposes.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim. May combine two claims.

    Study design and conductnone given

    Heart rate readings were collected in a random order across devices and averaged together to provide a measure of heart rate for each device during that stage.

    “These were collected in a random order across devices and averaged together to provide a measure of heart rate for each device during that stage.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductnone given

    Height was measured twice, and an optional third measurement was taken if the two measurements differed by 0.25 cm.

    “Height was measured twice, and an optional third measurement was taken if the 2 measurements differed by 0.25 cm.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Fitbit Charge HR has been found to underestimate heart rate and energy expenditure.

    “Fitbit Charge HR has been found to underestimate heart rate and EE [18]”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [18] source

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  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    Bland-Altman plots were examined for proportional bias.

    “Bland-Altman plots were examined for proportional bias.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Study design and conductnone given

    TrueOne 2400 volume and gas were calibrated before each trial.

    “TrueOne 2400 volume and gas were calibrated before each trial.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    The Borg Rating of Perceived Exertion scale value ranges from 6 to 20 and can be used to denote heart rates ranging from 60 to 200 beats per minute.

    “The scale value ranges from 6 to 20 and can be used to denote heart rates ranging from 60 to 200 beats per minute [29].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [29] Borg, GA, 1982, Med Sci Sports Exerc

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  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductnone given

    Weight was measured twice for each participant, and an optional third measurement was taken if the two measurements differed by 0.1 kg.

    “Weight was measured twice for each participant, and an optional third measurement was taken if the 2 measurements differed by 0.1 kg.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    The Apple Watch has been found to underestimate both heart rate and energy expenditure, with a tendency to underestimate calories expended by more than 100 calories.

    “The Apple Watch was found to underestimate both heart rate and EE, with a tendency to underestimate calories expended by more than 100 calories [18].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [18] source

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  • Classified as probably not a substantial claim.

    Premisecitation

    Heart rate measurement error increases with activity intensity for the Omron HR-500U and Mio Alpha when jogging, stair climbing, and using the stationary bike.

    “Investigators have found that heart rate measurement error increases with activity intensity for the Omron HR-500U and Mio Alpha when jogging, stair climbing, and using the stationary bike [21].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [21] source

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  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    PPG is a simple and low-cost optical technique that detects blood volume changes in the microvascular bed of tissue.

    “PPG is a simple and low-cost optical technique that detects blood volume changes in the microvascular bed of tissue [17].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [17] Allen, J, 2007, Physiol Meas source

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  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Premisenone given

    Most validation studies for Garmin devices focus on the Garmin Vivofit, although Forerunner models have been used in built environment studies.

    “For Garmin devices, most validation studies focus on the Garmin Vivofit, although Forerunner models have been used in built environment studies.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Heart rate response to exercise has been shown to be moderated by both knowledge about suggested levels of intensity and feedback in meeting those levels.

    “Heart rate response to exercise has been shown to be moderated by both knowledge about suggested levels of intensity as well as feedback in meeting those levels [22].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [22] Blanchard, EB, 1974, Psychophysiology source

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  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    The specific device selected (Fitbit #1 or Fitbit #2) and the location (right or left arm) for each of the 3 devices were randomized across participants.

    “The specific device selected (ie, Fitbit #1 or Fitbit #2) and location for each of the 3 devices (ie, right or left arm) were randomized across participants.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    More recent wearable physical activity devices that include a measure of heart rate utilize photoplethysmography (PPG) to measure heart rate.

    “These more recent wearable physical activity devices, which include a measure of heart rate, utilize photoplethysmography (PPG) to measure heart rate.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [17] Allen, J, 2007, Physiol Meas source

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  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Fitbit Charge HR has been found to have the greatest error in light to moderate physical activity and the least amount of error in vigorous physical activity.

    “with further examination showing the device to have the greatest error in light to moderate physical activity and least amount of error in vigorous physical activity [19].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [19] source

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  • Classified as probably not a substantial claim.

    Study design and conductreasoning

    To allow sufficient time for participants to reach steady state, heart rate was assessed 3.5 minutes into each stage of activity.

    “To allow sufficient time for participants to reach steady state, heart rate was assessed 3.5 minutes into each stage of activity.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    The Tanita BWB-800 scale was calibrated before each trial.

    “Weight was measured to the nearest 0.1 kg for each participant before participation and the scale was calibrated before each trial.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductown data

    A total of 62 individuals completed the protocol.

    “A total of 62 individuals completed the protocol.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Behavioral interventions utilizing Fitbit devices have found increased step count and daily physical activity minutes in both adults [5,30,31] and older adults [32].

    “Behavioral interventions utilizing Fitbit devices have found increased step count and daily physical activity minutes in both adults [5,30,31] and older adults [32].”
    Quote in the paperNot a substantial claim0 of 4 sources checked
    • cites [5] source

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    • cites [30] source

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    • cites [31] source

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    • cites [32] source

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  • May combine two claims.

    Premisecitation

    Heart rate feedback has been found to increase overall activity and percentage of time spent being vigorously active [23].

    “Likewise, heart rate feedback has been found to increase overall activity and percentage of time spent being vigorously active [23].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [23] source

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  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationcitation

    The increased error from previous studies for the Fitbit device [8,10] suggests that the Fitbit Charge HR may utilize heart rate in determining EE.

    “The increased error from previous studies for the Fitbit device [8,10] suggests that the Fitbit Charge HR may utilize heart rate in determining EE.”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [8] source

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    • cites [10] source

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  • May combine two claims.

    Premiseown data

    Apple Watch has been previously found to underestimate calories by more than 100 calories [18], whereas our study found the device to overestimate calories expended.

    “Apple Watch has been previously found to underestimate calories by more than 100 calories [18], whereas our study found the device to overestimate calories expended.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [18] source

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  • Probably not a substantial claim: may not pass S2 (checkable).

    Premisenone given

    An advantage and novel approach of the study is the examination of heart rate and energy expenditure at specific physical activity intensities.

    “An advantage and novel approach of the study is the examination of HR and EE at specific physical activity intensities.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S4 (based).

    Premisenone given

    This study provides one of the first validation assessments for the Fitbit Charge HR, Apple Watch, and Garmin Forerunner 225.

    “This study provides one of the first validation assessments for the Fitbit Charge HR, Apple Watch, and Garmin Forerunner 225.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning

    The lack of further anthropometric measures (ie, body fat percentage, waist to hip ratio) to aid in EE assessment could lead to increased errors in estimation.

    “The lack of further anthropometric measures (ie, body fat percentage, waist to hip ratio) to aid in EE assessment could lead to increased errors in estimation.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data

    These data suggest that, although these devices are useful as a stimulus to increase activity, each device is limited as an outcome measure or indicator of change in physical activity.

    “However, these data would suggest that, although these are useful as a stimulus to increase activity, each device is limited as an outcome measure or indicator of change in physical activity.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Following walking, participation in aerobics is most prevalent in younger women and running most prevalent among younger men [34].

    “Following walking, participation in aerobics is most prevalent in younger women and running most prevalent among younger men [34].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [34] DiPietro, L, 2001, J Gerontol A Biol Sci Med Sci source

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  • Probably not a substantial claim: may not pass S2 (checkable).

    Interpretationreasoning

    Because of the relative accuracy with heart rate, it is reasonable to suggest further field-testing with the Apple Watch and Fitbit Charge HR for heart rate.

    “However, because of the relative accuracy with heart rate, it is reasonable to suggest further field-testing with the Apple Watch and Fitbit Charge HR for heart rate.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Interpretationreasoning

    This study was conducted in a laboratory setting and therefore may not be generalizable to free-living activities.

    “This study was conducted in a laboratory setting and therefore may not be generalizable to free-living activities.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning

    This may be associated with the overestimation at baseline and recovery stages.

    “According to Garmin Ltd, the Forerunner 225 is a GPS running watch, which suggests that the EE algorithm is based solely on running activities, which may be associated with the overestimation at baseline and recovery stages.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationreasoning

    The EE algorithm is based solely on running activities.

    “According to Garmin Ltd, the Forerunner 225 is a GPS running watch, which suggests that the EE algorithm is based solely on running activities, which may be associated with the overestimation at baseline and recovery stages.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Self-monitoring of EE is significantly associated with weight loss and increased daily exercise [33].

    “Self-monitoring of EE is significantly associated with weight loss and increased daily exercise [33].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [33] source

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  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing).

    Interpretationcitation

    The addition of heart rate monitoring allows further opportunities for researchers to utilize these devices for interventions to increase physical activity and physical activity intensity.

    “Thus, the addition of heart rate monitoring allows further opportunities for researchers to utilize these devices for interventions to increase physical activity and physical activity intensity.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Premisenone given

    According to Garmin Ltd, the Forerunner 225 is a GPS running watch.

    “According to Garmin Ltd, the Forerunner 225 is a GPS running watch, which suggests that the EE algorithm is based solely on running activities, which may be associated with the overestimation at baseline and recovery stages.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    Given the observed heart rate variability between the Garmin Forerunner 225 relative to the Polar heart rate monitor, it is probably unnecessary to test in field-based studies, as it does not meet the standards of the criterion in highly controlled settings.

    “Given the observed heart rate variability between the Garmin Forerunner 225 relative to the Polar heart rate monitor, it is probably unnecessary to test in field-based studies, as it does not meet the standards of the criterion in highly controlled settings.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Walking is the most prevalent activity reported among all sociodemographic statuses [34].

    “For example, light-intensity activities are of particular importance as older adults tend to spend a greater portion of their day performing at this physical activity level [12], with walking as the most prevalent activity reported among all sociodemographic statuses [34].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [34] DiPietro, L, 2001, J Gerontol A Biol Sci Med Sci source

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  • Probably not a substantial claim: may not pass S2 (checkable).

    Interpretationnone given

    It is necessary to establish validity in a controlled setting, such as in a laboratory, in order to compare potential confounders that might be experienced in a field setting.

    “However, it is necessary to establish validity in a controlled setting, such as in a laboratory, in order to compare potential confounders that might be experienced in a field setting.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationreasoning

    Operating indoor run could be a reason the Apple Watch measured significantly higher EE at baseline and recovery stages.

    “Operating indoor run could be a reason the Apple Watch measured significantly higher EE at baseline and recovery stages.”
    Quote in the paperNot a substantial claim
50 of 50

  • The paper relies on this without support.

    Wearable devices are being used in weight loss interventions and could impact findings.

    “Establishing validity of wearable devices is of particular interest as these devices are being used in weight loss interventions and could impact findings.”

  • The authors state this as an assumption.

    This study is one of the first to examine the accuracy of consumer-grade activity tracking wearable devices in regard to heart rate.

    “To our knowledge, this is the first study to establish the validity of popular wearable devices at distinct physical activity intensities.”

  • The authors state this as an assumption.

    The study used a novel approach to measure accuracy of these devices for heart rate and EE at specific bouts of physical activity intensities.

    “The study used a novel approach to measure accuracy of these devices for heart rate and EE at specific bouts of physical activity intensities.”

  • The paper relies on this without support.

    Companies' updates to activity tracking wearable devices are often aesthetic, with no modification of the underlying technology.

    “However, these changes are often aesthetic, with no modification of the underlying technology.”

  • The paper relies on this without support.

    The Parvo Medics TrueOne 2400 metabolic cart and Polar heart rate monitor are valid criterion measures.

    “Parvo Medics TrueOne 2400 metabolic measurement system, which was used as the criterion measure.”
5 of 5

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

  • The two devices showed reasonable accuracy in HR and EE estimations under certain exercise conditions.

    “Similar to previous studies [13,28,30-32], we found reasonable accuracy in HR and EE estimations for these 2 devices under certain exercise conditions.”

    From Accuracy of Wrist-Worn Activity Monitors During Common Daily Physical Activities and Types of Structured Exercise: Evaluation Study (2018) · cites this paper as [30]

    The Discussion’s Principal Findings (page unavailable) describe reasonably accurate heart-rate readings for the Fitbit Charge HR under some conditions and accurate readings for the Garmin Forerunner 225 during vigorous activity. But the same section says energy-expenditure measurements were not accurate; the Results’ Energy Expenditure Overview reports an overestimation bias even where Fitbit estimates did not differ significantly from the criterion. The source studied three devices, so it cannot establish accuracy for the citing sentence’s unspecified ‘2 devices.’ (LLM, conf=0.87)

    Experimental — accuracy not yet measured

  • All trackers had a significant difference from ECG during low-intensity events.

    “All had a significant difference during low-intensity events.”

    From Sources of inaccuracy in photoplethysmography for continuous cardiovascular monitoring (2021) · cites this paper as [167]

  • The Apple Watch had the best MAPE (1.14-6.70%), while Fitbit Charge HR and Garmin Forerunner 225 had MAPE of 2.38-16.99% and 7.87-24.38%, respectively.

    “In another study, performed by Dooley et al., the comparison was made between the Apple Watch (AP), FB, and Garmin Forerunner 225 (GF), where the AP was considered the best in terms of MAPE (1.14–6.70%), while the FB and the GF had a MAPE of 2.38–16.99% and 7.87–24.38%, respectively [167].”

    From Sources of inaccuracy in photoplethysmography for continuous cardiovascular monitoring (2021) · cites this paper as [167]

  • The Apple Watch (p = 0.84) and Garmin Forerunner 225 (p = 0.35) had no significant difference in HR readings from the ECG during vigorous intensity.

    “The AP (p = 0.84) and GF (p = 0.35) had no significant difference in HR readings from the ECG during vigorous intensity.”

    From Sources of inaccuracy in photoplethysmography for continuous cardiovascular monitoring (2021) · cites this paper as [167]

  • Other studies have used suboptimal reference methods, such as chest straps or pulse oximeters, which themselves have a degree of error varying between 0 and 40 bpm when compared to electrocardiograms.

    “other studies have used suboptimal reference methods, such as the chest straps45–47 or pulse oximeters48, which themselves have a degree of error (varying between 0 and 40 bpm when compared to ECGs44).”

    From Guidelines for wrist-worn consumer wearable assessment of heart rate in biobehavioral research (2020) · cites this paper as [45]

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Discussion reverses the direction of Fitbit baseline heart rate

    Minor

    The discussion calls Fitbit's baseline heart-rate readings significantly higher, whereas Table 2 shows a lower mean than the Polar criterion. The results section also describes Fitbit's baseline readings as lower.

  • Fitbit baseline energy expenditure is described as higher despite a lower table mean

    Minor

    The text says Fitbit Charge HR measured higher energy expenditure at baseline, but Table 3 reports 11.80 kcal for Fitbit versus 12.97 kcal for the metabolic cart.

2 of 2

Cites

Flagged first, then by citations

Research works printed but not linked: 1

  1. Borg, GA, 1982, Med Sci Sports Exerc, 14, 377

Cited by

Sorted by citations

Related

Authors
Dooley, E. E., Golaszewski, N. M., & Bartholomew, J. B.
Affiliations
The University of Texas at Austin (US)
Corresponding author
Bartholomew, John B
ORCID
Venue
JMIR mHealth and uHealth
Publisher
JMIR Publications Inc.
Published
2017-03-16
Volume
5
Issue
3
Pages
e34
ISSN
2291-5222 (ISSN-L)
DOI
10.2196/mhealth.7043
PMC
PMC5374271
OpenAlex
W2595757535
Semantic Scholar
c84c28a040011dd108f5bccbbffb04baa9c06151
Cited by
242
References
29
Citations by year
2026: 14 · 2025: 15 · 2024: 23 · 2023: 22 · 2022: 37 · 2021: 39 · 2020: 27 · 2019: 32 · 2018: 26 · 2017: 7
FWCI
18.62
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)
Topics
  • Health Sciences › Medicine › Physiology › Physical Activity and Health
  • Physical Sciences › Computer Science › Computer Vision and Pattern Recognition › Context-Aware Activity Recognition Systems
  • Health Sciences › Health Professions › General Health Professions › Mobile Health and mHealth Applications
Keywords
wearable activity trackers, heart rate monitoring, energy expenditure estimation, exercise intensity, device validity, Apple Watch, wrist-worn devices, metabolic cart, chest strap, treadmill exercise, self-monitoring, consumer health technology, mean absolute percentage error, Bland-Altman analysis

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-09.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-09.

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

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