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Variable Accuracy of Wearable Heart Rate
Monitors during Aerobic Exercise
STEPHEN GILLINOV, MUHAMMAD ETIWY, ROBERT WANG, GORDON BLACKBURN, DERMOT PHELAN,
A. MARC GILLINOV, PENNY HOUGHTALING, HODA JAVADIKASGARI, and MILIND Y. DESAI
The Heart and Vascular Institute, Cleveland Clinic, Cleveland, OH
ABSTRACT
GILLINOV, S., M. ETIWY, R. WANG, G. BLACKBURN, D. PHELAN, A. M. GILLINOV, P. HOUGHTALING, H.
JAVADIKASGARI, and M. Y. DESAI. Variable Accuracy of Wearable Heart Rate Monitors during Aerobic Exercise. Med. Sci. Sports
Exerc., Vol. 49, No. 8, pp. 1697–1703, 2017. Purpose: Athletes and members of the public increasingly rely on wearable HR monitors to
guide physical activity and training. The accuracy of newer, optically based monitors is unconfirmed. We sought to assess the accuracy of
five optically based HR monitors during various types of aerobic exercise. Methods: Fifty healthy adult volunteers (mean TSD age = 38 T
12 yr, 54% female) completed exercise protocols on a treadmill, a stationary bicycle, and an elliptical trainer (Tarm movement). Each
participant underwent HR monitoring with an electrocardiogaphic chest strap monitor (Polar H7), forearm monitor (Scosche Rhythm+), and
two randomly assigned wrist-worn HR monitors (Apple Watch, Fitbit Blaze, Garmin Forerunner 235, and TomTom Spark Cardio), one on
each wrist. For each exercise type, HR was recorded at rest, light, moderate, and vigorous intensity. Agreement between HR measurements
was assessed using Lin"s concordance correlation coefficient (r
c
). Results: Across all exercise conditions, the chest strap monitor (Polar H7)
had the best agreement with ECG (r
c
= 0.996) followed by the Apple Watch (r
c
= 0.92), the TomTom Spark (r
c
= 0.83), and the Garmin
Forerunner (r
c
= 0.81). Scosche Rhythm+ and Fitbit Blaze were less accurate (r
c
= 0.75 and r
c
= 0.67, respectively). On treadmill, all devices
performed well (r
c
= 0.88–0.93) except the Fitbit Blaze (r
c
= 0.76). While bicycling, only the Garmin, Apple Watch, and Scosche Rhythm+
had acceptable agreement (r
c
90.80). On the elliptical trainer without arm levers, only the Apple Watch was accurate (r
c
= 0.94). None of
the devices was accurate during elliptical trainer use with arm levers (all r
c
G0.80). Conclusion: The accuracy of wearable, optically
based HR monitors varies with exercise type and is greatest on the treadmill and lowest on elliptical trainer. Electrode-containing chest
monitors should be used when accurate HR measurement is imperative. Key Words: WEARABLE HEART RATE MONITORS,
ACCURACY, RANDOMIZED TRIAL
Over the last decade, there has been a proliferation of
commercially available HR monitors and wearable
fitness devices. Targeting a larger audience than the
elite athletes who use HR monitoring to inform their training
and assess aerobic fitness, companies have entered the market
of population health, offering a variety of wearable HR and
activity monitoring systems to the public. Annual worldwide
sales of such devices are projected to reach 100,000,000 units
and $50 billion by 2019 (5,13,14).
Although many consumers purchase these wearable fitness
trackers to catalog their HR response to exercise, others use
them with the hope that they will improve health via weight
loss and/or increased aerobic fitness (3,4,10,12,13). However,
surveys document substantial attrition in the use of fitness
wearables, with up to one-third of individuals discontinuing
their use within 6 months of purchase (12).
In clinical practice, physicians and trainers frequently see
patients who report physiologic and behavioral data obtained
from their wearable devices; such data often include energy
expenditure, steps taken, sleep/wake times, and HR. Controlled
studies demonstrate variable accuracy of activity trackers, with
error margins approaching 25% for some devices (3,7,10,12,17).
A previous study suggests a somewhat lower error margin with
selected HR monitors (19).
Current questions regarding the accuracy of wearable HR
monitors are particularly relevant, given the recent consumer
shift from HR monitors that rely on chest straps with electrodes
that measure cardiac electrical activity toward more convenient
wrist-worn monitors that use optical sensing technology similar
to that used for pulse oximetry. Although the accuracy of chest
strap monitors has been confirmed in various previous reports
(6,18), there is a paucity of data validating the accuracy of
wrist-worn, optically based HR monitors (12). A recent study
from our group suggests that wrist-worn monitors fail to pro-
vide accurate readings during treadmill exercise; however, that
study examined only one form of exercise (treadmill walking/
running) and included first generation wrist-worn monitors,
one of which is no longer commercially available (19). Broad
Address for correspondence: Milind Y. Desai, M.D., Department of Car-
diovascular Medicine, Cleveland Clinic/Desk J1-5, Cleveland, OH 44195;
E-mail: desaim2@ccf.org.
Stephen Gillinov and Muhammad Etiwy are co-first authors and contributed
equally to the work.
Submitted for publication January 2017.
Accepted for publication March 2017.
0195-9131/17/4908-1697/0
MEDICINE & SCIENCE IN SPORTS & EXERCISE
Ò
Copyright Ó2017 by the American College of Sports Medicine
DOI: 10.1249/MSS.0000000000001284
1697
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assessment of the monitors"accuracy is important both for the
individuals who rely on these monitors to guide their athletic,
physical, and rehabilitative activity and for the physicians to
whom these individuals report their HR readings for the pur-
pose of potentially guiding therapy.
The objective of this study was to assess the accuracy of five
commonly used, currently commercially available, optically
based wearable HR monitors in an appropriately powered study
under various forms of aerobic exercise conditions.
METHODS
Participants
This prospective study recruited 50 healthy adults 18 yr or
older through fliers and Internet notices at Cleveland Clinic from
June 2016 through August 2016. Participants were screened to
ensure that they were able to safely perform an 18-min exercise
protocol, including a treadmill, an elliptical trainer, and a sta-
tionary bicycle. The screening tool was adapted from the Na-
tional Academy of Sports Medicine"s screening questionnaire
(11). Study exclusion criteria included known cardiovascular or
lung disease, presence of a cardiac pacemaker, treatment with
beta-blockers or heart rhythm medications, and self-reported
chest pain, dizziness, or loss of balance. The protocol was ap-
proved by the Institutional Review Board of the Cleveland
Clinic, and all subjects provided written informed consent. The
study was registered at clinicaltrials.gov (NCT02818244).
HR Monitors
All participants wore standard ECG leads (Mason-Likar
electrode placement of torso-mounted limb leads), a Polar H7
chest strap monitor, and a Scosche Rhythm+ on the forearm. In
addition, each participant was randomly assigned by a com-
puter program to wear two different wrist-worn HR monitors,
one on each wrist; this enabled the assessment of each type of
wrist-worn monitor in 25 subjects. The wrist-worn monitors
assessed included Fitbit Blaze (Fitbit), Apple Watch (Apple),
Garmin Forerunner 235 (Garmin), and TomTom Spark Cardio
(TomTom). Four units of each type of monitor were pur-
chased from retail outlets and studied in random order. Each of
these optically based wearable monitors measures HR via an
optically obtained plethysmogram that is processed according
to proprietary algorithms.
Exercise Protocol
In each subject, HR was assessed using five different moni-
toring modalities (ECG, Polar H7 chest strap, Scosche
Rhythm+, and two different wrist-worn monitors). The Mason–
Likar electrode placement allowed the assessment of modified
leads I, II, and III on ECG. An aggressive electrode preparation
was performed at each site, which included cleansing with al-
cohol and light abrasion to reduce resistance and optimizing
signal quality. ECG was monitored on a Quinton Q-tel RMS
telemetry system, and hard copy rhythm strips were obtained to
measure HR. ECG-based HR was determined by visual as-
sessment under direct supervision by a cardiologist. In addi-
tion, the HR was measured when performing four different
types of exercise at varying intensities; these included tread-
mill, stationary bicycle, elliptical trainer with arm levers, and
elliptical trainer without arm levers. The order of exercises
wasassignedrandomly.
Exercise protocols for each piece of equipment were as
follows:
Treadmill
)2 mph for 1.5 min
)3.5 mph for 1.5 min
)6 mph for 1.5 min
Stationary bicycle
)25 W for 1.5 min
)55 W for 1.5 min
)125 W for 1.5 min
Elliptical (without arm levers)
)Light for 1.5 min: crossramp = 1, resistance = 1, cadence =
60–70 min
j1
)Moderate for 1.5 min: crossramp = 1, resistance = 5,
cadence = 90–100 min
j1
)Vigorous for 1.5 min: crossramp = 10, resistance = 10,
cadence = 90–100 min
j1
Elliptical (with arm levers)
)Light for 1.5 min: crossramp = 1, resistance = 1, cadence =
60–70 min
j1
)Moderate for 1.5 min: crossramp = 1, resistance = 5,
cadence = 90–100 min
j1
)Vigorous for 1.5 min: crossramp = 10, resistance = 10,
cadence = 90–100 min
j1
The treadmill settings of 2, 3.5, and 6 mph correspond to
workloads of 2.5, 3.7, and 10.2 METs, respectively. For a 70-kg
individual, the bicycle settings of 25, 55, and 125 W correspond
to 2.4, 3.7, and 8.8 METs, respectively. Because there are no
standard workload settings for elliptical trainers, we identified
three settings that were judged to represent light, moderate, and
vigorous activity.
Each subject spent 4.5 min at each of the four exercise sta-
tions and then rested for 2 min between different exercise sta-
tions; therefore, total exercise time was 18 min, and total time of
each trial was 24 min. HR signals for all devices were checked
at the beginning of each exercise/rest segment to ensure device
function. HR was recorded from HR monitors at the completion
of each 1.5 min exercise segment and at the end of each 2 min
rest period; preliminary studies in three subjects confirmed that
HR had reached a steady state at these time points. At each
timepoint,HRwasrecordedbytwotrainedresearchper-
sonnel (SMG and ME), one situated on each side of the sub-
ject. HR recordings from all devices and ECG were obtained
for a period of approximately 5 s. Values were entered into an
IRB-approved database.
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Statistical Methods
Sample size. Sample size was based on the use of Lin"s
concordance correlation coefficient (r
c
) to compare HR
measurements with wearable, optically based HR monitors
to those obtained with the ECG, which is considered the
standard (10). On the basis of previous work, we deemed an
r
c
90.8 to represent acceptable accuracy in HR measure-
ment (20). Generation of 25 pairs of data for each device
(i.e., device and ECG) was necessary to provide 90% power
to determine a difference from r
c
of 0.82 to r
c
of 0.93.
Analysis plan. Paired differences. Using the ECG-
determined HR as the standard, each of the HR monitoring
systems was assessed for accuracy by calculation of the
difference between the measures and compared. The paired
differences, both relative and absolute, were calculated as
(HR
ecg
–HR
device
) for each device under the various con-
ditions. The absolute percent differences were calculated as
([HR
ecg
–HR
device
]/HR
ecg
100).
Agreement. The Bland–Altman analysis was performed
to assess agreement for each device with ECG (2). In addition,
Lin"s concordance correlation coefficients (r
c
) and associated
95% confidence intervals were calculated to provide a mea-
sure of agreement for each device with ECG. The concordance
correlation coefficient (r
c
) measures the degree to which the
paired observations fall on the identity line (9).
Multivariable testing. Repeated-measures mixed model
ANOVA was used to test the overall effect of the fitness
devices while adjusting for covariates and taking into account
multiple measurements for each subject. In addition to HR
device and exercise condition (activity type and intensity), factors
in the final adjusted model included age, gender, body mass in-
dex, wrist size, and days of typical aerobic exercise per week.
Data were analyzed using SAS version 9.4 (SAS Institute
Inc., Cary, NC) and R software version 3.2.3 (15).
Presentation. Continuous variables are reported as mean T
SD, with median and percentile values. Categorical variables
are reported as percent and frequency.
RESULTS
Subjects. The study randomized 50 subjects (mean TSD
age = 38 T12 yr, 27 [54%] females, 6 [12%] non-Whites)
(Table 1, Fig. 1). Subjects were examined for the presence of
tattoos on the wrist; none had tattoos in this location. All
subjects engaged in regular aerobic exercise (including
walking), and 82% reported that they exercised regularly to
the point of perspiration. Subjects"mean TSD resting HR on
ECG was 86 T18 bpm.
Aggregate results. Of the 4000 possible HR mea-
surements, 3985 were recorded (99.6%). Across all ECG
tracings, there was minimal artifact and in no situation did
ECG artifact interfere with visual HR determination. Miss-
ing data were attributable to failure of the device to record
HR (eight for Apple Watch, four for Fitbit, two for Scosche
Rhythm+, and one for Garmin Forerunner 235.
Measured HR ranged from 51 to 184 bpm. Average dif-
ferences from the ECG standard were less than 1 bpm for the
Polar H7 under all exercise conditions but extended to
nearly 20 bpm for other monitors (Table 2). The average
differences from the ECG standard were calculated as both
relative error (which averages positive and negative differ-
ences from the ECG standard) and the absolute value of error,
TABLE 1. Baseline characteristics of participants.
Characteristic Mean TSD 15th/50th/85th Percentiles Min, Max
Age (yr) 38 T12 26/33/52 21, 64
Height (cm) 171 T11 160/170/181 155, 198
Weight (kg) 73 T16 57/70/88 46, 118
Body mass index (kgIm
j2
)25T3.5 21.5/24/29 19, 33
Days per week of aerobic exercise (including walking) 4.6 T1.7 3/5/7 1, 7
Left wrist circumference (cm) 16 T1.4 14.5/15.4/17.5 13.4, 19.2
Right wrist circumference (cm) 16 T1.4 14.6/15.5/17.5 13.7, 19.6
Male 23 (46%) —
Nonwhite race 6 (12%)
Perspire during aerobic exercise 41 (82%) —
FIGURE 1—Flow of participants through the study.
VARIABLE ACCURACY OF HR MONITORS Medicine & Science in Sports & Exercise
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regardless of direction. HR values on the wrist-worn monitors
varied from the ECG standard by approximately 2% to nearly
20%, depending on the monitor and the activity (Table 2).
Bland–Altman analysis revealed that all monitors had some
measurements that did not reflect HR accurately (Fig. 2);
however, this variation was not linked to specific HR values,
meaning that variability was not influenced by the HR magni-
tude. The Apple Watch had 95% of differences fall within j17
and 20 bpm of the ECG, whereas TomTom Spark Cardio and
Garmin Forerunner 235 had 95% of values fall within j24 and
31 bpm and j27 and 33 bpm, respectively. The corresponding
values for Scosche Rhythm+ and Fitbit Blaze were j31 and
38 bpm and j30 and 45 bpm, respectively.
Under all conditions combined, when compared with
ECG, the Polar chest strap had the highest agreement with
ECG with an r
c
of 0.99. Among wrist-worn monitors, the
Apple Watch performed best with r
c
= 0.92, followed by the
TomTom Spark Cardio (r
c
= 0.83) and Garmin Forerunner
235 (r
c
= 0.81). The Scosche Rhythm+ and Fitbit Blaze had
r
c
= 0.75 and r
c
= 0.67, respectively (Fig. 3).
The results of the mixed model confirmed that among the
optically based HR monitors, the Apple Watch was the most
accurate, with no statistical difference from ECG (P= 0.22),
even after adjustment for all other factors. The other opti-
cally based HR monitors often underestimated the true HR
(PG0.0001). Subject factors (age, gender, body mass index,
wrist circumference, and days of typical aerobic exercise per
week) were not associated with HR monitor accuracy.
Agreement with ECG during various types of
exercise. The Polar H7 Chest Strap performed well during
all different aerobic exercise modalities (r
c
= 0.99), but other
HR monitors"agreement with ECG varied with the type of ex-
ercise (Table 2). At rest, all monitors had r
c
90.88. With the
treadmill, all devices provided acceptable agreement (r
c
=
0.88–0.93) except the Fitbit Blaze (r
c
= 0.76). While biking,
Garmin Forerunner 235, Apple Watch, and Scosche Rhythm+
had the highest agreement with ECG (r
c
90.80). On the el-
liptical trainer without using the arm levers, only the Apple
Watch provided readings that agreed with the ECG (r
c
=0.94).
None of the optically based HR monitors provided good
agreement with ECG during elliptical trainer use with the arm
levers engaged (r
c
G0.80).
Although HR monitor agreement with ECG varied with
the type of exercise, it did not vary with the intensity of
exercise from easy to moderate on each piece of equipment.
However, when moving to vigorous exercise, only the Ap-
ple Watch had readings with similar agreement to ECG to
those obtained with less intense exercise; all other monitors
had less agreement during vigorous activity (PG0.003).
DISCUSSION
The results of this study demonstrate that optically based
wearable HR monitors are less accurate than electrode-
containing chest strap monitors. In addition, the accuracy of
these monitors varies with the type of aerobic activity. These
TABLE 2. HR monitor differences from ECG according to activity.
Activity nDevice
HR (bpm) Differences from ECG
Agreement
r
c
Paired Relative
Difference
Paired Absolute
Difference
Absolute Percent
(%) Difference
Mean SD Mean SD Mean SD
Treadmill 150 Polar Chest Strap 0.4 3.1 1.2 2.9 1.1 2.4 0.99
149 Scosche Rhythm+ j2.8 11.3 6.3 9.8 5.9 9.7 0.92
71 Apple Watch j1.7 9.6 5.6 8.0 4.9 6.7 0.93
74 Fitbit 5.9 17.5 12.4 13.7 10.4 10.8 0.76
74 Garmin j0.3 11.2 7.3 8.5 6.1 7.0 0.92
75 TomTom 1.4 13.3 7.2 11.2 6.2 9.5 0.88
Bike 150 Polar Chest Strap 0.1 1.9 0.6 1.8 0.6 1.6 0.99
149 Scosche Rhythm+ 3.9 12.6 5.5 11.9 4.8 8.8 0.84
75 Apple Watch 3.1 10.2 4.6 9.6 4.1 7.8 0.88
73 Fitbit 18.2 25.2 18.9 24.6 15.9 18.2 0.41
75 Garmin 3.4 9.2 4.8 8.5 4.6 7.7 0.91
75 TomTom 6.7 14.3 7.0 14.2 5.9 10.7 0.77
Elliptical (no arms) 150 Polar Chest Strap 0.1 2.0 0.6 1.9 0.6 2.3 0.99
150 Scosche Rhythm+ 14.1 24.7 16.0 23.5 13.1 17.6 0.27
74 Apple Watch 0.6 6.6 3.5 5.6 3.2 4.9 0.94
74 Fitbit 10.0 15.9 11.6 14.8 9.8 11.5 0.58
75 Garmin 7.7 18.1 11.0 16.2 9.7 13.6 0.54
75 TomTom 7.3 19.4 8.0 19.1 6.4 13.4 0.55
Elliptical (with arms) 150 Polar Chest Strap 0.5 2.7 1.0 2.6 0.9 2.4 0.99
150 Scosche Rhythm+ 2.9 22.5 14.0 17.9 12.4 15.6 0.41
72 Apple Watch 5.5 13.6 7.4 12.7 6.5 10.8 0.75
75 Fitbit 2.1 20.2 13.8 14.9 11.7 12.1 0.48
75 Garmin 2.2 23.3 14.8 18.0 13.7 16.8 0.31
75 TomTom 1.4 14.0 8.0 11.6 6.7 9.6 0.76
Rest 200 Polar Chest Strap j0.3 1.0 0.7 0.8 0.8 1.0 0.99
200 Scosche Rhythm+ 1.1 6.2 3.9 4.9 4.6 6.0 0.93
100 Apple Watch j0.4 4.2 3.0 3.0 3.5 3.4 0.96
100 Fitbit 2.8 8.2 5.4 6.8 5.6 6.4 0.89
100 Garmin 1.1 8.1 5.0 6.5 5.9 7.5 0.88
100 TomTom 1.3 5.6 3.8 4.2 4.5 5.3 0.94
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findings raise questions concerning the role of such monitors
in individuals"management of their health, assessment of
their fitness, and guidance of their fitness regimens.
Introduced in the 1980s, chest strap–based HR monitors
function much like an ECG, sensing cardiac electrical ac-
tivity. Several studies confirm the accuracy of most of these
HR monitors under conditions of both rest and moderate
exercise (6,8,18). Although chest strap–based HR monitors
have been favored by elite athletes because of their proven
accuracy, they are relatively inconvenient and have not been
widely adopted by the public. By contrast, the recent intro-
duction of convenient, wrist-worn HR monitors that include
the capability for wireless transmission has stirred widespread
public interest in HR monitoring. However, as reported by
major media outlets, individuals"experiences with the
newer class of HR monitors suggest that their accuracy may
be poor, particularly during exercise (16). This controversy
has reached the courtroom in the form of a class action
lawsuit alleging that the Fitbit device is inaccurate and
potentially harmful (14).
The new wrist-worn HR monitors do not measure cardiac
electrical activity; rather, they rely on photoplethysmography.
The monitor illuminates the skin with an LED and then mea-
sures the amount of light reflected back to a photodiode
FIGURE 2—Bland–Altman plots and 95% limits of agreement with electrocardiographically measured HR. A, Polar H7; B, Apple Watch; C,
TomTom Spark; D, Garmin Forerunner 235; E, Scosche Rhythm+; F, Fitbit Blaze.
VARIABLE ACCURACY OF HR MONITORS Medicine & Science in Sports & Exercise
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sensor; this enables detection of variations in blood volume
associated with the pulse of blood caused by each cardiac
contraction. Potential sources of error with optically based
monitors include motion artifact from physical movement,
misalignment between the skin and the optical sensor, varia-
tions in skin color/tone, ambient light, and poor tissue perfu-
sion (1). The accuracy of such monitors during exercise is
controversial, some studies suggesting that wrist-worn HR
monitors perform best at rest or slow walking, and others
asserting assert good accuracy even during vigorous exercise
(1,5). In a recent study examining subjects on a treadmill, we
found variable accuracy between different optically based HR
monitors; however, when compared with an ECG, the tested
monitors all had a concordance correlation coefficient ex-
ceeding 0.80 (19).
Extending that work, the current study assessed the per-
formance of wearable HR monitors using varying aerobic
exercise modalities (treadmill, stationary bicycle, and elliptical
trainer with and without arms) and at different levels of in-
tensity. Recognizing that people engage in a variety of types of
FIGURE 3—Concordance correlation coefficients depicting agreement of device-measured HR with ECG. A, Polar H7; B, Apple Watch; C, TomTom
Spark; D, Garmin Forerunner 235; E, Scosche Rhythm+; F, Fitbit Blaze.
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exercise beyond walking on a treadmill, the primary purpose
of the current study was to assess the monitors"agreement with
ECG during different forms of aerobic activity. Distinct from
the previous study, the current study enrolled a new cadre of
subjects and assessed several monitors that had not previously
been tested. Although all monitors performed well in subjects
at rest, their accuracy varied with different exercise modalities.
Certain monitors were better suited for the stationary bicycle
and the elliptical trainer (without arm motion), and this may be
a result of variable tolerances for motion artifact associated
with different exercises. In particular, none of the optical
monitors performed well when assessing HR in subjects using
the elliptical trainer with arm motion, likely a result of motion
artifact related to arm movement (1). By contrast, a chest strap
containing an electrically based monitor provided accurate
measurements, regardless of exercise intensity or modality.
Although this study is the largest of its kind and included
nearly 4000 HR measurements, it has limitations. The cur-
rent study methodology (e.g., visual recording of HR on
ECG) may have contributed to some error as compared with
a more rigorous approach wherein time stamped raw device
data were extracted. The results apply only to the HR
monitors tested. These monitors were chosen because of
their apparent popularity with the public, and each monitor
was the manufacturer"s most recent offering at the time of
the study; however, they represent an opportunistic sample
of the wide range of available HR monitors. Continuous HR
assessment, which is currently not feasible with all devices,
would enable more detailed comparisons. The devices were
assessed in young, healthy volunteers exercising in a labo-
ratory setting. Results may vary for different subsets of in-
dividuals, including cardiac patients. Although we accounted
for participant factors including age and BMI, the relatively
narrow distribution of age and BMI in this study of young,
healthy volunteers does not enable us to rule out a potential
effect of these factors on the accuracy of HR measurement. In
addition, these results may not be representative of those
obtained during more vigorous exercise or during different
activities (e.g., running on pavement, swimming, or other
sports participation).
CONCLUSION
This study demonstrates that optically based wrist-worn HR
monitors vary in their accuracy and that their accuracy is ac-
tivity dependent. Individuals who use such monitors should be
aware of the possibility of inaccurate measurements and that
some monitors (i.e., the Apple Watch) provide greater agree-
ment with ECG than do other monitors. Apparently, spurious
HR measurements should be confirmed by simple palpation to
measure HR or, if readily available, by ECG. When accurate
HR monitoring is essential, an electrically based chest strap
monitor should be used.
This study was supported by the Mary Elizabeth Holdsworth Fund
at the Cleveland Clinic.
The Mary Elizabeth Holdsworth Fund had no role in the design
and conduct of the study; collection, management, analysis, and
interpretation of the data; preparation, review, or approval of the
manuscript; and decision to submit the manuscript for publication.
There are no relevant conflicts of interest to disclose.
The results of the present study do not constitute endorsement by
the American College of Sports Medicine. The results of the study
are presented clearly, honestly, and without fabrication, falsification,
or inappropriate data manipulation.
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