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PEER REVIEW HISTORY
BMJ Open publishes all reviews undertaken for accepted manuscripts. Reviewers are asked to
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are provided with free text boxes to elaborate on their assessment. These free text comments are
reproduced below.
ARTICLE DETAILS
TITLE (PROVISIONAL)
AUTHORS
Accuracy of a step counter during treadmill and daily life walking by
healthy adults and cardiac patients
Thorup, Charlotte; Andreasen, Jan; Sørensen, Erik; Gronkjaer,
Mette; Dinesen, Birthe; Hansen, John
VERSION 1 - REVIEW
REVIEWER
REVIEW RETURNED
GENERAL COMMENTS
Muaddi Alharbi
Charles Perkins Centre, University of Sydney, Sydney, Australia
04-May-2016
Introduction – There is a need to explain the benefits of physical
activity for healthy adults, not only for cardiac patients.
Introduction – Line 38 p. 4: you state:
One of Fitbit‟s step counters, the Fitbit Zip (Zip) (FITBIT, INC. 405
Howard StreetSan Francisco, Ca 94105) is small (35.6 Å~ 28.9 Å~
9.6 mm) and has a user account connected to a computer or mobile
application. The user account displays steps, active minutes,
distance and energy expenditure over time, providing the user with
knowledge of their own activity.
Please move this paragraph to the Methods section. Please see my
comment below in the methods section.
Introduction – Line 38 p. 5: you state “Researchers have agreed on
an acceptable level of inaccuracy at 3%". This sentence may be
confusing or unclear to the reader. It would be useful to clarify that
there is no universally accepted definition of acceptable degree of
error for physical activity wearable devices. Some studies
recommend that an acceptable measurement error under controlled
conditions or for research purposes is within ±3% (Schneider,
Crouter, & Bassett, 2004; Tudor-Locke et al., 2006) and under freeliving conditions is within ±10% (Schneider et al., 2004; Tudor-Locke
et al., 2006). Other studies recommend that mean errors of less than
20% have acceptable validity for clinical purposes (Schneider,
Crouter, Lukajic, & Bassett, 2003).
Introduction – Pleases provide scientific and clinical background for
the reference standard and the rationale for choosing the reference
standard.
Aims – Can you please re-state your aims clearly.
Methods – Line 38 p. 5: you state:
The descriptive statistics for the sample populationare provided in
Table 1. The gender distribution was equal with ten males (mean
age 34 ± 12.5) and ten females (mean age 44 ± 13.95). The overall
mean age was 39±13.79, and the mean BMI was 26± 6.
Also line 38 p. 5: you state:
The descriptive statistics of the patients are provided in Table 2. The
overall mean age was 67±10.03, and the mean BMI was 28±2.69.
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There were no significant differences between the two treatment
groups in either age or BMI.
Please create a subheading in the Results section titled “Sample
characteristics” and move these paragraphs under this subheading.
Methods – Table 1 and Table 2. Please combined them in one table
and move it from the Methods section to the Results section. Please
also provide clinical characteristics of cardiac patients either in the
text or in the Table. This may include, but not be limited to,
cardiovascular diagnosis, comorbidities, and medications that may
influence outcome measures.
Methods – There is a need to create a subheading titled “Measures”
and briefly describe the measures (i.e. Fitbit Zip, treadmill and the
Shimmer) used in your study. Also, briefly report if there is evidence
as to their validity and reliability.
Results – The data in Table 4 are exactly the same as in Table 3.
Please provide the actual data for Table 4.
Discussion – There is a need for clear guidance according to the
study outcomes. Thus, I expected this article to give clear messages
and practical information for Fitbit and to highlight the different
validity criteria between the tested and criterion PA measures for
clinical purposes (e.g. <20%) compared to research purposes
(within ± 3%).
Discussion –You might like to consider including the paper by
Alharbi et al. 2016; Validation of Fitbit-Flex as a measure of freeliving physical activity in a community-based phase III cardiac
rehabilitation population in your list of references and contrasting
your results with those reported in this particular study. Please
revise and comment.
Discussion and conclusion – There is need to consider the validity of
Fitbit not only for to research purposes (within ± 3%) but also its
validity for clinical purposes (i.e. <20%)
Figures – It is quite difficult to visualise the intended information.
Please use dashed horizontal lines to illustrate the limits of
agreement and a solid horizontal line to illustrate the mean
difference.
General comment – There is no justification to combine two studies
[„Real-life study‟ and „Treadmill study‟] in one manuscript. You
should separate them.
General comment – There is a need to report in Tables 3 and 4 the
mean ± SD for the Fitbit and Shimmer in order to verify your percent
relative error calculation.
General comment – The abbreviation TP24h is used for the first time
on line 34, p. 9. Please write out in full.
General comment – The manuscript may need proofreading to
improve its clarity.
REVIEWER
REVIEW RETURNED
Alexander HK Montoye
Ball State University, United States of America
11-May-2016
GENERAL COMMENTS
Major comments:
- Page 4 Line 16-18. The authors attribute the lack of use of physical
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activity monitors to limited validity and reliability studies. Their
sentence is a bit too strongly worded. These monitors are heavily
used, at least by the general population, and there are numerous
recent studies evaluating accuracy of these devices for different
activities and in different populations.
- The primary purpose of this study seems to be evaluating accuracy
of the Zip in a clinical population. However, the healthy individuals
chosen for the lab protocol were much younger than the clinical
population. Why did the authors decide not to age-match the healthy
sample to the clinical sample? Age-matching may have given better
confidence that the results in the healthy individuals would translate
to the clinical population. Moreover, the gender distribution of the
clinical population is not given (please add to Methods), but it is
likely that it is predominately male. Gender-matching would have
further given generalizability to the results. The authors should
consider addressing these as limitations in the Discussion section.
- Page 7 line 26: Please don‟t use the word “proven”. “shown” would
be more appropriate. Also, in what population, setting (lab vs. freeliving) and activities was this validated for? Please provide more
information.
- Page 8 line 13-18: How does a 24-hour assessment take 1-10
days? Please provide more detail on why some participants wore
the monitor so much longer than others when it was only supposed
to be a 24-hour protocol. Same comment for home activity, only
taking 24-hours of 4 weeks. How was the day chosen? What were
the criteria for choosing this day?
- Page 8 line 36-40: Why was steps/min from the Zip taken? Need to
state what the purpose of doing this was rather than just total steps.
Same for Raw Z-gyro data from Shimmer.
- Statistical analysis section: Why were averages taken for the Zips?
In the real-world, no one would use 2 devices and average the data
together to get their physical activity level. Accuracy should be
assessed using individual Zip monitors instead of averaged data,
especially since the real-life study did not do averaging.
- Page 10 lines 26-28: What is “unacceptably high deviation”? need
to define what the threshold is for high deviation.
- Page 11 Table 3 and 4. First of all, Tables 3 and 4 are identical,
which the reviewer believes must be an error. Also, how did the
authors match speeds in the real-life to those that were used in the
treadmill study? This is very unclear. Additionally, how much data
were available for each speed? The reviewer has difficulty believing
that there was very much time that cardiac patients spent at 6.1
km/hr.
- Discussion is very short and lacks detail on study findings and
implications. More detail is needed.
- Page 14 lines 11-18: The fact that the Shimmer likely shifted is
very concerning considering that it is the criterion measure for the
study. More detail is needed to discuss why we should trust this as a
criterion measure.
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Minor comments:
- Page 5 Line 38-41 and Table 1. Be consistent with number of
places past the decimal point for your means and SDs.
- Page 7 line 11: change to “four Zips on elastic belts”
- Page 7 line 15: change to “triaxial” from three axial
- Page 7 line 18: can say that the formulas are proprietary since no
one except the company knows them
- Page 7 line 40: Please list out the speeds so that the study could
be replicated.
- Figure 3: “Relative” spelled incorrectly
- Page 12 line 28-29: “Tudor-Locke” spelled incorrectly
- Page 14 line 4: Validity, not reliability
REVIEWER
REVIEW RETURNED
GENERAL COMMENTS
Christopher Barr
Flinders University
Australia
26-May-2016
With the prevalence of these devices, this type of study is important
to ensure that they are not used in situations where they underreport steps and can become demotivational in the rehabilitaiton
setting. The paper is worth while, however I have a few concerns,
listed below.
The introduction sets the scene well for the study.
In the methods:
Table 1 is mostly a replication of the text, and table 2 could also be
removed if a little more information is added to the text. Alternatively,
the text could be shortened and tables 1 and 2 combined
For the purposes of assessing error, the results of the two fitbits
worn were averaged. Can the authors justify this? In real life a
person would only wear one fitbit, so if they are attempting to
discuss the accuracy of the fitbit in real life then it would make sense
to report the accuracy of a single device.
When assessing the walking speed in the real life situation, what is
the estimated error in walking speed calculation? Within this
calculation there appears to be an assumption of step length based
on hight, which may not hold true for slow walking populations such
as those with cardiac disease. It is also unclear if walking was
evident in the full 3 minute sections, or just within the 3 minutes.
Inactivity at the beginning or end of the 3 minute period would also
affect the speed estimation. Much of the walking activity, especially
around the home, will include stops within a 3 minute period.
In a few places in the manuscript, notably the study limitations and
the discussion, the authors state that accuracy of the fitbit zip at
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different speeds / body locations is unknown. The accuracy of the
Zip has been tested at different speeds, locations, and cadence in
the paper by Singh et al.
Singh, A. K., Farmer, C., Van Den Berg, M. L., Killington, M., & Barr,
C. J. (2015). Accuracy of the FitBit at walking speeds and cadences
relevant to clinical rehabilitation populations. Disability and Health
Journal.
The discussion on page 13 mentions patietns with chronic heart
failure had a shorter step length. This can impact on the accuracy of
the fitbit in the study population and should be acknowledged.
VERSION 1 – AUTHOR RESPONSE
Reviewer 1: Muaddi Alharbi
2 1Introduction – Line 38 p. 4: you state: One of Fitbit‟s step counters, the Fitbit Zip (Zip) (FITBIT,
INC. 405 Howard StreetSan Francisco, Ca 94105) is small (35.6 Å~ 28.9 Å~ 9.6 mm) and has a user
account connected to a computer or mobile application. The user account displays steps, active
minutes, distance and energy expenditure over time, providing the user with knowledge of their own
activity. Please move this paragraph to the Methods section. Please see my comment below in the
methods section.
Answer: Thank you for this practical remark, this sentence is now placed at the methods section (line
13 p. 6).
3 Introduction – Line 38 p. 5: you state “Researchers have agreed on an acceptable level of
inaccuracy at 3%". This sentence may be confusing or unclear to the reader. It would be useful to
clarify that there is no universally accepted definition of acceptable degree of error for physical activity
wearable devices. Some studies recommend that an acceptable measurement error under controlled
conditions or for research purposes is within ±3% (Schneider, Crouter, & Bassett, 2004; Tudor-Locke
et al., 2006) and under free-living conditions is within ±10% (Schneider et al., 2004; Tudor-Locke et
al., 2006). Other studies recommend that mean errors of less than 20% have acceptable validity for
clinical purposes (Schneider, Crouter, Lukajic, & Bassett, 2003).
Answer: Thank you for this helpful remark, clarification is now done (Line 23 p. 4 – line 11 p. 5).
4 Introduction – Pleases provide scientific and clinical background for the reference standard and the
rationale for choosing the reference standard.
Answer: Correction is made (Line 23 p. 4 – line 11 p. 5).
5 Aims – Can you please re-state your aims clearly?
Answer: Clarification is now done and a hypothesis for the real life study is set (Line 23 p. 4 – line 11
p. 5).
6 Methods – Line 38 p. 5: you state: The descriptive statistics for the sample population are provided
in Table 1. The gender distribution was equal with ten males (mean age 34 ± 12.5) and ten females
(mean age 44 ± 13.95). The overall mean age was 39±13.79, and the mean BMI was 26± 6. Also line
38 p. 5: you state: The descriptive statistics of the patients are provided in Table 2. The overall mean
age was 67±10.03, and the mean BMI was 28±2.69. There were no significant differences between
the two treatment groups in either age or BMI. Please create a subheading in the Results section
titled “Sample characteristics” and move these paragraphs under this subheading.
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Answer: I appreciate this useful observation and sample characteristic are moved to the result section
(Line 21 page 9).
7 Methods – Table 1 and Table 2. Please combined them in one table and move it from the Methods
section to the Results section. Please also provide clinical characteristics of cardiac patients either in
the text or in the Table. This may include, but not be limited to, cardiovascular diagnosis,
comorbidities, and medications that may influence outcome measures.
Answer: Correction is made and one joint table is moved to the result section. Cardiovascular
diagnosis and treatment are added (table 1 page 10).
8 Methods – There is a need to create a subheading titled “Measures” and briefly describe the
measures (i.e. Fitbit Zip, treadmill and the Shimmer) used in your study. Also, briefly report if there is
evidence as to their validity and reliability.
Answer: I acknowledge this constructive remark and changes are made (line 10 – 24 p. 6).
9 Results – The data in Table 4 are exactly the same as in Table 3. Please provide the actual data for
Table 4.
Answer: The correct table 4 is displayed (table 3 page 12).
10 Discussion – There is a need for clear guidance according to the study outcomes. Thus, I
expected this article to give clear messages and practical information for Fitbit and to highlight the
different validity criteria between the tested and criterion PA measures for clinical purposes (e.g.
<20%) compared to research purposes (within ± 3%).
Answer: I acknowledge this constructive remark and because of the added hypothesis for the real life
study, the discussion has provided more clear outcomes (page 13 – 14).
11 Discussion –You might like to consider including the paper by Alharbi et al. 2016; Validation of
Fitbit-Flex as a measure of free-living physical activity in a community-based phase III cardiac
rehabilitation population in your list of references and contrasting your results with those reported in
this particular study. Please revise and comment.
Answer: Thank you for this helpful remark, the interesting paper is now used in the discussion (page
13 – 14).
12 Discussion and conclusion – There is need to consider the validity of Fitbit not only for to research
purposes (within ± 3%) but also its validity for clinical purposes (i.e. <20%).
Answer: This is now addressed in the discussion and conclusion (page 13 – 14 and line 16 page 15).
13 Figures – It is quite difficult to visualise the intended information. Please use dashed horizontal
lines to illustrate the limits of agreement and a solid horizontal line to illustrate the mean difference.
Answer: The horizontal lines are now illustrated differently (Figure 6).
14 General comment – There is no justification to combine two studies [„Real-life study‟ and „Treadmill
study‟] in one manuscript. You should separate them.
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Answer: I appreciate this useful observation, but we decide to keep both studies in one paper.
15 General comment – There is a need to report in Tables 3 and 4 the mean ± SD for the Fitbit and
Shimmer in order to verify your percent relative error calculation.
Answer: Thank you for this practical remark mean and ± SD is now presented (table 2 and 3).
16 General comment – The abbreviation TP24h is used for the first time on line 34, p. 9. Please write
out in full
Answer: Correction is made (line 2 page 9).
17 General comment – The manuscript may need proofreading to improve its clarity.
Answer: A person, competent in the English language, has performed proofreading.
Reviewer 2: Alexander HK Montoye
18 Page 4 Line 16-18. The authors attribute the lack of use of physical activity monitors to limited
validity and reliability studies. Their sentence is a bit too strongly worded. These monitors are heavily
used, at least by the general population, and there are numerous recent studies evaluating accuracy
of these devices for different activities and in different populations.
Answer: Thank you for this useful comment, the word limited is replaced by cautious (line 7 p. 4).
19 The primary purpose of this study seems to be evaluating accuracy of the Zip in a clinical
population. However, the healthy individuals chosen for the lab protocol were much younger than the
clinical population. Why did the authors decide not to age-match the healthy sample to the clinical
sample? Age-matching may have given better confidence that the results in the healthy individuals
would translate to the clinical population. Moreover, the gender distribution of the clinical population is
not given (please add to Methods), but it is likely that it is predominately male. Gender-matching
would have further given generalizability to the results. The authors should consider addressing these
as limitations in the Discussion section.
Answer: I acknowledge this constructive remark. Gender distribution of the clinical population is now
added in the methods and the above mentioned problems are now shortly addressed in the
discussion section (Line 19 p 5 & line 1 page 6 and table 1 page 10 and discussion).
20 Page 7 line 26: Please don‟t use the word “proven”. “shown” would be more appropriate. Also, in
what population, setting (lab vs. free-living) and activities was this validated for? Please provide more
information.
Answer: Proven is replaced by shown (line 22 page 6) and further information on population is
mentioned (table 1 page 10).
21 Page 8 line 13-18: How does a 24-hour assessment take 1-10 days? Please provide more detail
on why some participants wore the monitor so much longer than others when it was only supposed to
be a 24-hour protocol. Same comment for home activity, only taking 24-hours of 4 weeks. How was
the day chosen? What were the criteria for choosing this day?
Answer: Clarification is now done (line 3 and 4 page 8).
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22 Page 8 line 36-40: Why was steps/min from the Zip taken? Need to state what the purpose of
doing this was rather than just total steps. Same for Raw Z-gyro data from Shimmer.
Answer: Thank you for this helpful remark, clarification is now done (Line 9 page 8).
23 Statistical analysis section: Why were averages taken for the Zips? In the real-world, no one would
use 2 devices and average the data together to get their physical activity level. Accuracy should be
assessed using individual Zip monitors instead of averaged data, especially since the real-life study
did not do averaging.
Answer: Thank you for this useful comment, all data are now displayed in the table 2-3 and used in
the result and discussion section.
24 Page 10 lines 26-28: What is “unacceptably high deviation”? need to define what the threshold is
for high deviation.
Answer: Clarification is made (Line 20 page 15).
25 Page 11 Table 3 and 4. First of all, Tables 3 and 4 are identical, which the reviewer believes must
be an error. Also, how did the authors match speeds in the real-life to those that were used in the
treadmill study? This is very unclear. Additionally, how much data were available for each speed? The
reviewer has difficulty believing that there was very much time that cardiac patients spent at 6.1 km/h.
Answer: Thank you for this helpful remark. The correct table 4 is displayed and clarification about
speed calculations is made (Line 8-16 page 9 and table 3).
26 Discussion is very short and lacks detail on study findings and implications. More detail is needed.
Answer: Detailed discussion is now provided (Discussion).
27 Page 14 lines 11-18: The fact that the Shimmer likely shifted is very concerning considering that it
is the criterion measure for the study. More detail is needed to discuss why we should trust this as a
criterion measure.
Answer: Clarification is made (Line 13 page 15).
28 Minor comments:
a. Page 5 Line 38-41 and Table 1. Be consistent with number of places past the decimal point for your
means and SDs Page 7 line 11: change to “four Zips on elastic belts”
b. Page 7 line 15: change to “triaxial” from three axial
c. Page 7 line 18: can say that the formulas are proprietary since no one except the company knows
them
d. Page 7 line 40: Please list out the speeds so that the study could be replicated.
e. Figure 3: “Relative” spelled incorrectly
f. Page 12 line 28-29: “Tudor-Locke” spelled incorrectly
g. Page 14 line 4: Validity, not reliability
Answer: All minor comments are now corrected.
29 Reviewer 3: Christopher Barr
30 In the methods: table 1 is mostly a replication of the text, and table 2 could also be removed if a
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little more information is added to the text. Alternatively, the text could be shortened and tables 1 and
2 combined.
Answer: Table 1 and 2 are combined and the text is shortened (table 1).
31 For the purposes of assessing error, the results of the two fitbits worn were averaged. Can the
authors justify this? In real life a person would only wear one fitbit, so if they are attempting to discuss
the accuracy of the fitbit in real life then it would make sense to report the accuracy of a single device.
Answer: Thank you for this practical remark. All results from all fitbits are now shown in the table and
addressed throughout the text (table 3).
32 When assessing the walking speed in the real life situation, what is the estimated error in walking
speed calculation? Within this calculation there appears to be an assumption of step length based on
hight, which may not hold true for slow walking populations such as those with cardiac disease. It is
also unclear if walking was evident in the full 3 minute sections, or just within the 3 minutes. Inactivity
at the beginning or end of the 3 minute period would also affect the speed estimation. Much of the
walking activity, especially around the home, will include stops within a 3 minute period.
Answer: Thank you for this useful comment, clarification is now made and the potential error for
walking speed in the real life situation is addressed in the limitation section Line 8-10 page 9).
33 In a few places in the manuscript, notably the study limitations and the discussion, the authors
state that accuracy of the fitbit zip at different speeds / body locations is unknown. The accuracy of
the Zip has been tested at different speeds, locations, and cadence in the paper by Singh et al. Singh,
A. K., Farmer, C., Van Den Berg, M. L., Killington, M., & Barr, C. J. (2015). Accuracy of the FitBit at
walking speeds and cadences relevant to clinical rehabilitation populations. Disability and Health
Journal.
Answer: Thank you for this useful comment. The paper from Singh is now addressed in the
discussion and limitation (Discussion and limitation).
34 The discussion on page 13 mentions patietns with chronic heart failure had a shorter step length.
This can impact on the accuracy of the fitbit in the study population and should be acknowledged.
Answer: A miner revision of this section is made in the attempt to address this study population
(Discussion).
VERSION 2 – REVIEW
REVIEWER
REVIEW RETURNED
GENERAL COMMENTS
Muaddi Alharbi
Charles Perkins Centre, University of Sydney,Australia
05-Oct-2016
Introduction – There is still a need to explain the benefits of physical
activity for healthy adults, not only for cardiac patients.
Introduction – Line 38 p. 4: you state:
One of Fitbit‟s step counters, the Fitbit Zip (Zip) (FITBIT, INC. 405
Howard StreetSan Francisco, Ca 94105).
Please move this description to the Methods section.
General comment – There is no justification to combine two studies
[„Real-life study‟ and „Treadmill study‟] in one manuscript.
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REVIEWER
REVIEW RETURNED
GENERAL COMMENTS
Alexander HK Montoye
Assistant Professor of Integrative Physiology and Health Science,
Alma College, USA
28-Sep-2016
- Thank you to the authors for performing the revisions to this paper.
The paper is markedly improved from the original version.
- This reviewer‟s only remaining concern with content of the paper is
that more detail is still needed in the Discussion section. Examples
include the following areas. 1) More detail is needed as to the quality
of the criterion measure for slow speeds (if it works poorly, then the
Zip might actually be more or less accurate than you‟ve reported). 2)
The fact that errors were high in the free living is very concerning.
The authors mention this, but I think it deserves more
acknowledgement and discussion since this will have real
implications for whether this monitor (and its placement) are
recommended for use in cardiac populations. 3) Page 15 lines 8-9,
do you have a reference that these devices would actually be able to
detect changes over time? We can‟t just assume that to be true.
- The grammar still needs improvement. One example is provided (in
Table 1, it‟s “Height”, not “high”), but there are many instances in
which sentence wordings need work.
VERSION 2 – AUTHOR RESPONSE
Reviewer 2: Alexander HK Montoye
1. This reviewer‟s only remaining concern with the content of the paper is that more detail is still
needed in the Discussion section. Examples include the following areas: 1) More detail is needed as
to the quality of the criterion measure for slow speeds (if it works poorly, then the Zip might actually be
more or less accurate than you‟ve reported); 2) The fact that errors were high in the free living is very
concerning. The authors mention this, but I think it deserves more acknowledgement and discussion
since this will have real implications for whether this monitor (and its placement) are recommended for
use in cardiac populations; and 3) Page 15 lines 8-9, do you have a reference that these devices
would actually be able to detect changes over time? We can‟t just assume that to be true.
a. Answer: Thank you for these useful comments regarding the discussion section.
i. With regards to 1), criterion measure (the Shimmer) is expected to have high accuracy and, to the
best of our knowledge, it does not work poorly, even at slow speeds. In addition, having the Shimmer
turned upside down did not matter for readings, as every step was still detectable. Shown in A, below
is the gyro-Z-axis for the Shimmer (surgical patient nr. 2), and shown in B. is what it would look like if
the Shimmer was turned upside down.
A.
B.
ii. Regarding 2), this comment is interesting. The research group behind this study believes that all
research should have real implications for the population under study. We do not advise against the
use of the Zip in cardiac patients, we just state that a speed of 3.6 km/h or higher is required to obtain
an accurate measurement of steps using the Zip. This might be challenging for cardiac patients who
walk at a slower pace, and step accuracy of 24 hour real-life measurements seems challenging.
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However, the Zip might motivate cardiac patients to walk more (see in the conclusions).
iii. As for 3), a reference has been added (ref. 46)
2. The grammar still needs improvement. One example is provided (in Table 1, it‟s “Height”, not
“high”), but there are many instances in which sentence wordings need work.
a. Answer: Proofreading was performed by AJE (see attached certificate).
Reviewer 1: Muaddi Alharbi
1. Introduction – There is still a need to explain the benefits of physical activity for healthy adults, not
only for cardiac patients.
a. Answer: Thank you for this suggestion; the benefits of physical activity for healthy adults are
included in the introduction (line 1-6 p. 4).
2. Introduction – Line 38 p. 4: you state: One of Fitbit‟s step counters, the Fitbit Zip (Zip) (FITBIT, INC.
405 Howard Street San Francisco, Ca 94105). Please move this description to the Method section
a. Answer: The company name is now included in the methods section (Line 18 p. 6).
3. General comment – There is no justification to combine two studies [„Real-life study‟ and „Treadmill
study‟] in one manuscript.
a. Answer: We appreciate this useful remark, and to a degree, you are correct. However, the authors
have decided not to separate the two studies into two papers because the knowledge regarding
speed is directly transferrable to the estimates of time-periods with evident walking (TP3min) and
makes figure 5 possible.
VERSION 3 – REVIEW
REVIEWER
REVIEW RETURNED
Muaddi Fahad Alharbi
Charles Perkins Centre, University of Sydney, Australia
20-Dec-2016
GENERAL COMMENTS
Thanks for your detailed responses and editions made in the text
following the reviewers' recommendations. The paper was surely
improved with these changes.
REVIEWER
Alexander HK Montoye
Assistant Professor of Integrative Physiology and Health Science
Alma College
USA
09-Dec-2016
REVIEW RETURNED
GENERAL COMMENTS
Thank you to the authors for there comments and revisions. My
concerns have been appropriately addressed.
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Accuracy of a step counter during treadmill
and daily life walking by healthy adults and
patients with cardiac disease
Charlotte Brun Thorup, Jan Jesper Andreasen, Erik Elgaard Sørensen,
Mette Grønkjær, Birthe Irene Dinesen and John Hansen
BMJ Open 2017 7:
doi: 10.1136/bmjopen-2016-011742
Updated information and services can be found at:
http://bmjopen.bmj.com/content/7/3/e011742
These include:
References
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