AUTHOR’S RESPONSE TO REVIEWER’S COMMENTS 5/22/2022
The authors wish to thank the Editor and Reviewers for their invaluable suggestions.
The manuscript has been revised according to the editor’s and reviewers’ comments.
A point-by-point reply is given below. The line, figure and table numbers noted in
the replies refer to the revised manuscript. In the following response, the editor’s
and reviewer’s comments are shown in italics and our responses appear immediately
below in normal type.
Editor:
Journal Requirements:
When submitting your revision, we need you to address these additional requirements.
1. Please ensure that your manuscript meets PLOS ONE's style requirements, including
those for file naming. The PLOS ONE style templates can be found at
https://journals.plos.org/plosone/s/file?id=wjVg/PLOSOne_formatting_sample_main_body.pdf and
https://journals.plos.org/plosone/s/file?id=ba62/PLOSOne_formatting_sample_title_authors_affiliations.pdf
Reply: We thank the Editor for the comments. We have formatted the main body and title
of the manuscript accordingly to meet PLOS ONE’s style requirements.
2. In your Data Availability statement, you have not specified where the minimal data
set underlying the results described in your manuscript can be found. PLOS defines
a study's minimal data set as the underlying data used to reach the conclusions drawn
in the manuscript and any additional data required to replicate the reported study
findings in their entirety. All PLOS journals require that the minimal data set be
made fully available. For more information about our data policy, please see http://journals.plos.org/plosone/s/data-availability.
Upon re-submitting your revised manuscript, please upload your study’s minimal underlying
data set as either Supporting Information files or to a stable, public repository
and include the relevant URLs, DOIs, or accession numbers within your revised cover
letter. For a list of acceptable repositories, please see http://journals.plos.org/plosone/s/data-availability#loc-recommended-repositories. Any potentially identifying patient information must be fully anonymized.
Important: If there are ethical or legal restrictions to sharing your data publicly,
please explain these restrictions in detail. Please see our guidelines for more information
on what we consider unacceptable restrictions to publicly sharing data: http://journals.plos.org/plosone/s/data-availability#loc-unacceptable-data-access-restrictions. Note that it is not acceptable for the authors to be the sole named individuals
responsible for ensuring data access.
We will update your Data Availability statement to reflect the information you provide
in your cover letter.
Reply: We thank the Editor for the comment. Temporarily, we have made our data available
at the following link
https://estudusfqedu-my.sharepoint.com/:f:/g/personal/parauz_usfq_edu_ec/EhXWpdGUuiBHsoomPt2-LYMBo54z04eM9wKcmxkeWGQVeA?e=aSeMbS
However, upon acceptance of the manuscript, we will make all our data available in
a public repository.
3. We note that you have stated that you will provide repository information for your
data at acceptance. Should your manuscript be accepted for publication, we will hold
it until you provide the relevant accession numbers or DOIs necessary to access your
data. If you wish to make changes to your Data Availability statement, please describe
these changes in your cover letter and we will update your Data Availability statement
to reflect the information you provide.
Reply: We thank the Editor for the comment. Temporarily, we have made our data available
at the following link
https://estudusfqedu-my.sharepoint.com/:f:/g/personal/parauz_usfq_edu_ec/EhXWpdGUuiBHsoomPt2-LYMBo54z04eM9wKcmxkeWGQVeA?e=aSeMbS
However, upon acceptance of the manuscript, we will make all our data available at
a public repository.
In addition, we have explained the data availability information in our cover letter.
Reviewer #1
Reviewer #1: Overall, a nice publication on gait symmetry in healthy individuals.
Gait symmetry is an interesting parameter for diagnostics and therapy control. The
presented methods seem suitable for further analysis. Nevertheless, a detailed explanation
of the method and the comparison with other methods and results for gait symmetry
is missing. The argumentation presented in the introduction and discussion included
good arguments, underlined by references. But, there already exists some literature
about gait symmetry in patients and healthy individuals, which has to be mentioned.
The state of the art is missing and the purpose of this new study is not clear.
Reply: We thank and acknowledge the Reviewer for the comments. The Introduction and
Discussion Sections have been revised accordingly in order to increase clarity for
readership. A more detailed state of the art has been introduced and discussed, and
the purpose of the study has been clarified.
Line 62-74:
Gait symmetry has been suggested as an important indicator of gait function in impaired
and healthy individuals [14-16]. Consequently, better implementation and evaluation
of restorative interventions requires appropriate assessment and characterization
of normative gait symmetry in healthy individuals. Several studies have investigated
on gait symmetry [17-23], as well as on spine and lower body kinematics during gait
[6, 8, 9, 24-27]. Despite such contributions, up to date, there is no generally accepted
standard for assessing symmetry [23]. Typically, the symmetry index, symmetry ratio,
and statistical approaches are implemented to determine gait symmetry [21]. Thus,
it is complicated to compare among studies and establish standard criteria to guide
clinical decision-making. Several studies have implemented statistical procedures
to investigate interlimb asymmetries using the mean difference between left and right
limbs as a symmetry parameter in pathological individuals [15, 16, 28, 29]. However,
implementation of such approaches to determine reference degree of asymmetry information
in healthy individuals is lacking.
Line 80-88:
Therefore, the purpose of the present study was to analyze 3D spine, pelvis, and lower
body gait symmetry kinematics during normal and fast treadmill walking in healthy
individuals. This study applies statistical parametric mapping (SPM) [12], detecting
significant differences between left and right-side movements, as well as the normalized
symmetry index [21, 23] approaches to determine spine, pelvis, and lower body asymmetries.
We hypothesized that there are significant differences between the spine and pelvis
angular movements associated with the left lower limb motions and spine and pelvis
angular movements associated with the right lower limb motions, as well as between
the left and right lower extremity joint angles during normal and fast treadmill walking
in healthy individuals.
Line 374-394:
Previous studies have investigated spine and lower body gait kinematics [6, 8, 9,
24-27]. In addition, although several studies have investigated on gait symmetry [17-23,
45] and presented valuable information, there is not generally accepted standard for
characterization of gait symmetry [23]. Asymmetric gait patterns in healthy individuals
may be expected as there exist natural functional differences between the lower extremities
[12, 41, 43], such as the contribution of each limb in carrying out the tasks of propulsion
and control during able-bodied walking [43]. The present study provides information
not only on the degree of asymmetry, the mean angular difference between left and
right sides, but also on the SInorm in healthy individuals during normal and fast
treadmill walking. Such information will add to the knowledge provided by previous
investigations to better understand spine, pelvis, and lower body motions in healthy
individuals. Our findings on SInorm for lower body motions in the sagittal plane were
comparable to the ones described in [23]. Moreover, this study adds information on
the SInorm parameter by describing the spine and pelvis 3D angular motions. In addition,
reference degree of asymmetry information in healthy individuals has been presented
in this study to help in the biomechanical assessment pathological individuals. Although
the use of this indicator may be confusing as it is not referenced to the joint range
of motion, such indicator has been implemented to assess asymmetry in pathological
individuals. For instance, the degrees of asymmetry reported in total hip [16, 28,
29] and knee [15] replacement patients are greater than the degrees of asymmetry observed
in the present study. Consequently, degrees of asymmetry greater than the ones reported
in this study may be an indicative of abnormal gait function.
The gait symmetry, as the described result, is presented on over 10 pages. Discussed
were differences between the degree of asymmetry, which is questionable, as this parameter
is not referenced to the different range of motions of different movements. In addition,
differences in gait symmetry between normal and fast walking were discussed, but not
statistically analyzed. The most relevant question, which parameter defines the symmetry
is not mentioned and discussed in comparison with existing literature. Moreover, comparing
the gait symmetry during different movements, first, the gait symmetry in different
participants should be analyzed. All in all, the goal of the paper is not clear.
Reply: We agree and thank the Reviewer for the insightful comments. Even though the
degree of asymmetry is not referenced to the different ranges of motions of different
movements, it is a parameter that has been reported in the literature, for example:
1. Arauz P, Peng Y, Kwon Y-M. Knee motion symmetry was not restored in patients with
unilateral bi-cruciate retaining total knee arthroplasty—in vivo three-dimensional
kinematic analysis. International orthopaedics 42(12): 2817, 2018
2. Arauz P, Peng Y, MacAuliffe J, Kwon Y-M. In-vivo 3-Dimensional gait symmetry analysis
in patients with bilateral total hip arthroplasty. Journal of biomechanics 77: 131,
2018
3. Tsai T-Y, Dimitriou D, Li J-S, Woo Nam K, Li G, Kwon Y-M. Asymmetric hip kinematics
during gait in patients with unilateral total hip arthroplasty: In vivo 3-dimensional
motion analysis. Journal of Biomechanics 48(4): 555, 2015
Nevertheless, in order to increase clarity for readership, in addition to the degree
of asymmetry, the normalized symmetry index has been calculated and discussed accordingly.
Figures 3, 4, 5, and 6, as well as Tables 1 and 2 have been revised accordingly. Likewise,
Table 3, describing the result of the normalized symmetry index has been included.
Furthermore, the information from the normalized symmetry index has been used to statistically
analyze the differences between normal and fast treadmill walking.
The degree of asymmetry and the normalized symmetry index have been described and
discussed accordingly to make the paper clearer.
The purpose of the study has been revised to increase the clarity for readership.
Line 170-174:
Symmetry was calculated throughout the gait cycle for spine, pelvis, and lower body
motions. Statistical parametric mapping and the normalized symmetry index, presented
by Gouwanda et al. [21], were calculated for assessing gait symmetry of the spine
and pelvis angular motions, as well as lower body joint angles. The normalized symmetry
index (SInorm) was calculated based on Eq. 1 [19-21, 23].
Line 333-342:
Descriptive statistics of the SInorm and its comparison between normal and fast treadmill
walking is presented in Table 3. Overall, greater asymmetries were found during fast
treadmill walking than normal treadmill walking.
Table 3. Descriptive statistics of the maximum SInorm in % and its comparison between
normal and fast treadmill walking for N=60 participants.
Segment Motion Treadmill Walking Normal Treadmill Walking Fast
Mean SD Max Min Mean SD Max Min p-value
Upper Thorax Posterior-Anterior Tilt 45.56 12.47 66.67 12.70 44.17 12.61 65.61 12.64
0.201
Ipsi-Contra Lateral Tilt 13.87 11.07 60.71 0.56 15.36 12.07 63.82 0.84 0.109
Contra-Ipsi Lateral Rotation 22.28 14.08 64.70 0.81 22.59 12.30 58.93 1.28 0.765
Lower Thorax Posterior-Anterior Tilt 44.88 11.76 66.50 15.60 42.42 11.28 65.84 9.50
0.019
Ipsi-Contra Lateral Tilt 15.11 11.30 56.47 0.46 17.82 12.17 59.03 0.00 0.000
Contra-Ipsi Lateral Rotation 13.60 9.13 60.25 2.03 13.69 10.75 66.07 0.54 0.919
Upper Lumbar Posterior-Anterior Tilt 42.05 11.84 66.67 9.69 41.35 11.09 66.67 16.63
0.422
Ipsi-Contra Lateral Tilt 13.77 10.86 64.38 0.00 13.65 10.10 59.13 0.18 0.867
Contra-Ipsi Lateral Rotation 10.87 8.21 64.26 1.05 11.42 9.24 66.67 0.41 0.456
Lower Lumbar Posterior-Anterior Tilt 37.29 12.85 66.67 11.15 37.79 12.95 66.67 12.54
0.574
Ipsi-Contra Lateral Tilt 14.82 10.16 55.32 0.00 15.90 11.83 59.77 0.59 0.163
Contra-Ipsi Lateral Rotation 14.51 9.99 56.92 0.05 16.82 11.77 63.86 0.75 0.002
Pelvis Posterior-Anterior Tilt 38.10 14.02 66.67 6.40 37.77 13.83 66.67 4.94 0.770
Ipsi-Contra Lateral Tilt 9.83 10.20 65.57 0.28 10.49 11.56 62.98 0.05 0.474
Contra-Ipsi Lateral Rotation 12.25 8.51 50.01 0.67 11.88 8.95 59.82 0.29 0.602
Hip Flexion-Extension 7.98 10.13 65.29 0.15 8.18 8.86 60.56 0.33 0.787
Adduction-Abduction 15.39 15.10 66.67 0.84 16.40 14.69 66.62 1.59 0.372
Internal-External Rotation 28.46 15.05 66.06 3.25 29.51 13.59 63.38 5.99 0.164
Knee Flexion-Extension 6.62 6.64 61.39 0.63 7.71 6.19 62.62 0.40 0.045
Adduction-Abduction 29.80 16.00 66.05 2.38 30.33 13.42 63.55 2.61 0.545
Internal-External Rotation 30.06 13.17 62.85 6.59 27.71 12.44 62.08 4.34 0.009
Ankle Dorsi-Plantar Flexion 11.77 9.08 66.67 0.64 10.91 7.88 58.57 1.045 0.294
Eversion-Inversion 21.22 10.39 57.16 1.87 22.97 11.76 63.11 1.98 0.036
Internal-External Rotation 30.00 14.85 66.61 1.17 31.13 14.18 66.67 1.22 0.261
Abbreviations: SD, standard deviation; Max, maximum; Min, minimum.
Line 374-394:
Previous studies have investigated spine and lower body gait kinematics [6, 8, 9,
24-27]. In addition, although several studies have investigated on gait symmetry [17-23,
45] and presented valuable information, there is not generally accepted standard for
characterization of gait symmetry [23]. Asymmetric gait patterns in healthy individuals
may be expected as there exist natural functional differences between the lower extremities
[12, 41, 43], such as the contribution of each limb in carrying out the tasks of propulsion
and control during able-bodied walking [43]. The present study provides information
not only on the degree of asymmetry, the mean angular difference between left and
right sides, but also on the SInorm in healthy individuals during normal and fast
treadmill walking. Such information will add to the knowledge provided by previous
investigations to better understand spine, pelvis, and lower body motions in healthy
individuals. Our findings on SInorm for lower body motions in the sagittal plane were
comparable to the ones described in [23]. Moreover, this study adds information on
the SInorm parameter by describing the spine and pelvis 3D angular motions. In addition,
reference degree of asymmetry information in healthy individuals has been presented
in this study to help in the biomechanical assessment pathological individuals. Although
the use of this indicator may be confusing as it is not referenced to the joint range
of motion, such indicator has been implemented to assess asymmetry in pathological
individuals. For instance, the degrees of asymmetry reported in total hip [16, 28,
29] and knee [15] replacement patients are greater than the degrees of asymmetry observed
in the present study. Consequently, degrees of asymmetry greater than the ones reported
in this study may be an indicative of abnormal gait function.
In addition, some words are used confusingly. For example, talking about motion analysis
‘rotation’ is used to describe the movement of a joint in one plane, often in the
transversal plane. In contrast, in the presented manuscript rotation is also used
to talk about the general motion in all planes. Be careful to use the common vocabulary
of the field. Other vocabularies are mentioned in the detailed comments.
Reply: We agree and thank the Reviewer for the comments. All words and terminology
have been revised accordingly to make the manuscript clearer.
In conclusion, the analysis of gait symmetry based on objective motion parameters
is a rising and important field, which can be supported by the presented methods.
Nevertheless, the manuscript needs to be mainly restructured and is not acceptable
in its current form.
Reply: We agree and thank the Reviewer for the comments. All comments have been addressed,
and the manuscript has been revised and restructured accordingly in order to increase
the clarity for readership.
Detailed corrections and comments can be found below:
Abstract:
• Missing the description of how symmetry was calculated.
Reply: We agree and thank the Reviewer for the insightful comment. The description
of the approaches used to determine symmetry have been described accordingly in Abstract.
Line 34-36:
Statistical parametric mapping and the normalized symmetry index approaches were used
to determine spine, pelvis, and lower body asymmetries during treadmill walking.
• Moreover, it is confusing, first talking only about rotation and mentioning afterward
also tilt and knee flexion. See the comment in the summary for the usage of the word
‘rotation’.
Reply: We agree and thank the Reviewer for the comments. All words and terminology
have been revised accordingly to make the manuscript clearer.
Line 36-41:
The spine and pelvis angular motions associated with the left and right lower limb
motions, as well as the left and right lower extremity joint angles were compared
for normal and fast treadmill walking. The lower lumbar contra-ipsi lateral rotation
(5.74±0.04°) and hip internal rotation (5.33±0.18°) presented the largest degrees
of asymmetry during normal treadmill. Upper lumbar ipsi-contra lateral tilt (1.48±0.14°)
and knee flexion (2.98±0.13°) indicated the largest asymmetries and during fast treadmill
walking.
• Line 37: I think it should be ‘rotation’ and not ‘notation’.
Reply: We agree and thank the Reviewer for the comments. All words and terminology
have been revised accordingly to make the manuscript clearer.
Line 38-41:
The lower lumbar contra-ipsi lateral rotation (5.74±0.04°) and hip internal rotation
(5.33±0.18°) presented the largest degrees of asymmetry during normal treadmill. Upper
lumbar ipsi-contra lateral tilt (1.48±0.14°) and knee flexion (2.98±0.13°) indicated
the largest asymmetries and during fast treadmill walking.
• Line 38: What is meant by upper ipsilateral tilt? What is the joint you are talking
about?
Reply: We thank the Reviewer for the comment. The sentence has been revised accordingly
to make the manuscript clearer.
Line 38-41:
The lower lumbar contra-ipsi lateral rotation (5.74±0.04°) and hip internal rotation
(5.33±0.18°) presented the largest degrees of asymmetry during normal treadmill. Upper
lumbar ipsi-contra lateral tilt (1.48±0.14°) and knee flexion (2.98±0.13°) indicated
the largest asymmetries and during fast treadmill walking.
Introduction:
• Gait symmetry was calculated in different ways, but there is no information about
the way how to calculate gait symmetry.
Reply: We agree and thank the Reviewer for the comment. Information on the approaches
used to calculate gait symmetry has been included in the Introduction Section accordingly
in order to increase clarity for readership.
Line 65-74:
Several studies have investigated on gait symmetry [17-23], as well as on spine and
lower body kinematics during gait [6, 8, 9, 24-27]. Despite such contributions, up
to date, there is no generally accepted standard for assessing symmetry [23]. Typically,
the symmetry index, symmetry ratio, and statistical approaches are implemented to
determine gait symmetry [21]. Thus, it is complicated to compare among studies and
establish standard criteria to guide clinical decision-making. Several studies have
implemented statistical procedures to investigate interlimb asymmetries using the
mean difference between left and right limbs as a symmetry parameter in pathological
individuals [15, 16, 28, 29]. However, implementation of such approaches to determine
reference degree of asymmetry information in healthy individuals is lacking.
Line 80-84:
Therefore, the purpose of the present study was to analyze 3D spine, pelvis, and lower
body gait symmetry kinematics during normal and fast treadmill walking in healthy
individuals. This study applies statistical parametric mapping (SPM) [12], detecting
significant differences between left and right-side movements, as well as the normalized
symmetry index [21, 23] approaches to determine spine, pelvis, and lower body asymmetries.
• Last paragraph: Again the question arises, why you are talking only about joint
rotations? 3D movements are described in most cases as flexion-extension; abduction-adduction
and internal-external rotation. Therefore it is confusing to talk only about rotations
if 3D kinematics will be analyzed.
Reply: We agree and thank the Reviewer for the comments. All words, sentences, and
terminology have been revised accordingly to make the manuscript clearer.
Line 84-88:
We hypothesized that there are significant differences between the spine and pelvis
angular movements associated with the left lower limb motions and spine and pelvis
angular movements associated with the right lower limb motions, as well as between
the left and right lower extremity joint angles during normal and fast treadmill walking
in healthy individuals.
Methods:
• Line 82: What are most participants? And how did you control the dominant leg?
Reply: We thank the Reviewer for the comment. We have made clear in the Methods Section
that fifty-two participants reported to be right-dominant. This has been included
as a study limitation as no action was taken to control the dominant leg.
Line 94-95:
Fifty-two out of the sixty participants reported to be right-leg dominant (with leg
dominance being defined as the preferred leg for kicking a ball).
Line 394-397:
Several limitations need to be considered to interpret the present results. To begin
with, the average age of the male and female participants in this study was ~21 years
old, 52 out of 60 participants reported to be right-dominant, and all participants
reported a healthy lifestyle (exercised at least twice a week); hence, results may
be limited to similar populations.
• Procedure and data collection: What about a calibration measurement?
Reply: We thank the Reviewer for the comment. We have made clear in the Methods Section
that a standard Vicon calibration procedure was applied to determine the three-dimensional
coordinated of each reflective spherical marker.
Line 111-112:
The standard Vicon calibration procedures were applied to determine the 3D coordinates
of the reflective spherical markers.
• Line 149-50: Is there a reference about the procedure you used for heel-contact
and toe-off detection? In addition, I would be happy about some more information about
this procedure of gait event detection.
Reply: We agree thank the Reviewer for the comment. This sentence has been revised
and referenced in the Methods Section accordingly in order to increase the clarity
for readership.
Line 164-165:
Strides were defined to start with the initial contact and end with the following
initial contact of one foot [23].
• Statistical analysis:
o Only the SPM was described and no other statistical tests which were used.
Reply: We agree and thank the Reviewer for the comment. All statistical test used
in this study have been described accordingly in the Methods Section in order to increase
the clarity for readership.
Line 179-186:
The software MATLAB (MathWorks, Inc., Natick, MA) was used to performed SPM [12, 36-38]
analyses using scalar fields to determine significant differences between the spine
and pelvis angular motions associated with the left lower limb motions, and spine
and pelvis angular motions associated with the right lower limb motions, as well as
between the left and right hip, knee, and ankles joint angles throughout the gait
cycle. A Student’s t-test was used to compare maximum SInorm differences between normal
and fast treadmill walking. Likewise, A Student’s t-test compared walking speeds for
each condition. A significance level of α = 0.05 was used for the analysis.
o In the references, the SPM with the help of python was described in contrast to
the mentioned software MATLAB. I would prefer more suitable references.
Reply: We thank the Reviewer for the comment. SPM was first used in python and then
implemented in MATLAB. The references used are suitable because SPM methodology and
software application is explained. One more reference was included to indicate SPM
application with both python and MATLAB in order make the manuscript clearer for the
reader.
1. Pataky TC, Vanrenterghem J, Robinson MA. The probability of false positives in
zero-dimensional analyses of one-dimensional kinematic, force and EMG trajectories.
Journal of Biomechanics 49(9): 1468, 2016
Line 179-186:
The software MATLAB (MathWorks, Inc., Natick, MA) was used to performed SPM [12, 36-38]
analyses using scalar fields to determine significant differences between the spine
and pelvis angular motions associated with the left lower limb motions, and spine
and pelvis angular motions associated with the right lower limb motions, as well as
between the left and right hip, knee, and ankles joint angles throughout the gait
cycle. A Student’s t-test was used to compare maximum SInorm differences between normal
and fast treadmill walking. Likewise, A Student’s t-test compared walking speeds for
each condition. A significance level of α = 0.05 was used for the analysis.
o Moreover, the threshold, mentioned in the results section, is not explained.
Reply: We agree and thank the Reviewer for the insightful comment. The Results Section
has been revised and the SPM threshold has been included accordingly. The SPM threshold
is calculated automatically by using the SPM 1D function in MATALB. The threshold
value must be exceeded to detect significant differences.
Line 193-194:
SPM analysis indicated that the upper and lower thorax segments presented symmetrical
angular motions during normal treadmill walking, as the scalar field SPM curve did
not exceed the threshold t* for α = 0.05 (Fig. 3).
Figure 3:
Results:
• Line 166: What is meant by ‘spine gait’? I would talk about asymmetric spine motion
during normal treadmill walking.
Reply: We agree and thank the Reviewer for the comment. The sentence has been revised
in the Results Section accordingly in order to increase clarity for readership.
Line 192:
Asymmetric spine motion during normal treadmill walking
• Line 170: What is meant by the degree of asymmetry averages? Is it possible to describe
or visualize how this parameter is defined?
Reply: We agree and thank the Reviewer for the insightful comment. We have made clear
in the Results Section that the average degree of asymmetry describes the mean difference
between left and right-side movements when SPM detected significant differences.
Line 242-245:
Descriptive statistics of the average degree of asymmetry, describing the mean difference
between left and right-side movements when the scalar field SPM detected significant
differences, and the maximum magnitude of the SInorm when the scalar field SPM detected
significant differences, in spine segments during normal and fast treadmill walking
are presented in Table 1.
• Line 189: Please explain the threshold you describe.
Reply: We agree and thank the Reviewer for the insightful comment. The Results Section
has been revised and the SPM threshold has been included accordingly. The SPM threshold
is calculated automatically by using the SPM 1D function in MATALB. The threshold
value must be exceeded to detect significant differences.
Line 193-194:
SPM analysis indicated that the upper and lower thorax segments presented symmetrical
angular motions during normal treadmill walking, as the scalar field SPM curve did
not exceed the threshold t* for α = 0.05 (Fig. 3).
Figure 3:
• Line 189-90: Left side angles cannot be greater and lesser than right side angles
at the same time, they can be greater or lesser.
Reply: We agree and thank the Reviewer for the comment. The sentence has been revised
in the Results Section accordingly in order to increase clarity for readership.
Line 209-216:
Fig 3. Average and standard deviation of upper thorax, lower thorax, upper lumbar,
and lower lumbar posterior-anterior (P/A) tilt, ipsi-contralateral (Ipsi/Con) tilt,
and contra-ipsi (Con/Ipsi) rotation, for left and right sides during one gait cycle
of normal treadmill walking (TWN) in sixty healthy participants. Green bars on the
horizontal axis and the scalar field SPM results with threshold t* depict where, in
% cycle, left side angles were greater or lesser than right side angles. The normalized
symmetry index (SInorm) calculated during one gait cycle of TWN. Solid and dashed
lines correspond to average left and right sides, as well as average SInorm, and shaded
areas correspond to standard deviation. Black dotted vertical lines denote toe-off.
Figure 3:
• Line 199: Again, ‘spine gait’?
Reply: We agree and thank the Reviewer for the comment. The sentence has been revised
in the Results Section accordingly in order to increase clarity for readership.
Line 218:
Asymmetric spine motions during fast treadmill walking
• Line 202: It should be ‘asymmetrical motion’ or ‘no asymmetry’.
Reply: We agree and thank the Reviewer for the comment. The sentence has been revised
in the Results Section accordingly in order to increase clarity for readership.
Line 218-223:
SPM analysis showed that the upper and lower thorax segments presented symmetrical
angular motions during fast treadmill walking (Fig. 4). SInorm values for upper and
lower thorax posterior anterior tilt varied between ±36% whereas the ipsi-contra lateral
tilt and contra-ipsi lateral rotation varied between ±17% (Fig. 4). SPM indicated
that upper and lower lumbar angular motions were asymmetrical. The upper lumbar indicated
a symmetrical posterior-anterior tilt, with SInorm values varying between ±25% (Fig.
4).
Figure 4:
• Line 218: Again threshold?
Reply: We agree and thank the Reviewer for the insightful comment. The Results Section
has been revised and the SPM threshold has been included accordingly. The SPM threshold
is calculated automatically by using the SPM 1D function in MATALB. The threshold
value must be exceeded to detect significant differences. Fig. 4 illustrates examples
of thresholds t* for different motions.
Line 124-128:
Average and standard deviation of upper thorax, lower thorax, upper lumbar, and lower
lumbar posterior-anterior (P/A) tilt, ipsi-contralateral (Ipsi/Con) tilt, and contra-ipsi
(Con/Ipsi) rotation, for left and right sides during one gait cycle of fast treadmill
walking (TWF) in sixty healthy participants. Green bars on the horizontal axis and
the scalar field SPM results with threshold t* depict where, in % cycle, left side
angles were greater or lesser than right side angles. The normalized symmetry index
(SInorm) calculated during one gait cycle of TWF. Solid and dashed lines correspond
to average left and right sides, as well as average SInorm, and shaded areas correspond
to standard deviation. Black dotted vertical lines denote toe-off.
Figure 4:
• Line 222 and 262: What is meant by ‘lower body gait’? Lower body or lower limb motion
sounds better.
Reply: We agree and thank the Reviewer for the comment. The sentence has been revised
in the Results Section accordingly in order to increase clarity for readership.
Line 257:
Asymmetric lower body motions during normal treadmill walking
• It is not necessary to mention the results in the text and the table. A reference
to the table is enough.
Reply: We agree and thank the Reviewer for the comment. The Results Section has been
revised accordingly to increase the clarity for the readership.
Line 242-245:
Descriptive statistics of the average degree of asymmetry, describing the mean difference
between left and right-side movements when the scalar field SPM detected significant
differences, and the maximum magnitude of the SInorm when the scalar field SPM detected
significant differences, in spine segments during normal and fast treadmill walking
are presented in Table 1.
Line 321-325:
Descriptive statistics of the average degree of asymmetry, describing the mean difference
between left and right-side movements when the scalar field SPM detected significant
differences, and the maximum magnitude of the SInorm when the scalar field SPM detected
significant differences, in the pelvis segment and lower body joints during normal
and fast treadmill walking are presented in Table 2.
Line 333-335:
Descriptive statistics of the SInorm and its comparison between normal and fast treadmill
walking is presented in Table 3. Overall, greater asymmetries were found during fast
treadmill walking than normal treadmill walking.
Discussion:
• Line 300: I think it should be ‘hip internal rotation’ and not ‘notation’.
Reply: We agree and thank the Reviewer for the comment. The sentence has been revised
in the Discussion Section accordingly in order to increase clarity for readership.
Line 349-352:
Degrees of asymmetry and the associated maximum magnitude of SInorm of 5.74±0.04°
and 14%, as well as 5.33±0.18° and 21%, for the lower lumbar contra-ipsi lateral rotation
and hip internal rotation, respectively, were the largest asymmetries detected during
normal treadmill walking.
• Line 301: Be precise, what ‘upper ipsilateral tilt’? Talking about the upper lumbar
ipsilateral tilt is understandable.
Reply: We agree and thank the Reviewer for the comment. The sentence has been revised
in the Discussion Section accordingly in order to increase clarity for readership.
Line 352-355:
Upper lumbar ipsi-contra lateral tilt and knee flexion-extension with degrees of asymmetry
and the associated the maximum magnitude of SInorm of 1.48±0.14° and 15.3%, as well
as 2.98±0.13° and 6.5%, respectively, were the largest asymmetries found during fast
treadmill walking.
• Comparing the symmetry or asymmetry of normal and fast treadmill walking is questionable
if the gait symmetry between the participants is not analyzed.
Reply: We agree and thank the Reviewer for the insightful comment. The information
from the normalized symmetry index has been used to statistically analyze the differences
between normal and fast treadmill walking. Those results have been introduced and
discussed accordingly.
Line 333-342:
Descriptive statistics of the SInorm and its comparison between normal and fast treadmill
walking is presented in Table 3. Overall, greater asymmetries were found during fast
treadmill walking than normal treadmill walking.
Table 3. Descriptive statistics of the maximum SInorm in % and its comparison between
normal and fast treadmill walking for N=60 participants.
Segment Motion Treadmill Walking Normal Treadmill Walking Fast
Mean SD Max Min Mean SD Max Min p-value
Upper Thorax Posterior-Anterior Tilt 45.56 12.47 66.67 12.70 44.17 12.61 65.61 12.64
0.201
Ipsi-Contra Lateral Tilt 13.87 11.07 60.71 0.56 15.36 12.07 63.82 0.84 0.109
Contra-Ipsi Lateral Rotation 22.28 14.08 64.70 0.81 22.59 12.30 58.93 1.28 0.765
Lower Thorax Posterior-Anterior Tilt 44.88 11.76 66.50 15.60 42.42 11.28 65.84 9.50
0.019
Ipsi-Contra Lateral Tilt 15.11 11.30 56.47 0.46 17.82 12.17 59.03 0.00 0.000
Contra-Ipsi Lateral Rotation 13.60 9.13 60.25 2.03 13.69 10.75 66.07 0.54 0.919
Upper Lumbar Posterior-Anterior Tilt 42.05 11.84 66.67 9.69 41.35 11.09 66.67 16.63
0.422
Ipsi-Contra Lateral Tilt 13.77 10.86 64.38 0.00 13.65 10.10 59.13 0.18 0.867
Contra-Ipsi Lateral Rotation 10.87 8.21 64.26 1.05 11.42 9.24 66.67 0.41 0.456
Lower Lumbar Posterior-Anterior Tilt 37.29 12.85 66.67 11.15 37.79 12.95 66.67 12.54
0.574
Ipsi-Contra Lateral Tilt 14.82 10.16 55.32 0.00 15.90 11.83 59.77 0.59 0.163
Contra-Ipsi Lateral Rotation 14.51 9.99 56.92 0.05 16.82 11.77 63.86 0.75 0.002
Pelvis Posterior-Anterior Tilt 38.10 14.02 66.67 6.40 37.77 13.83 66.67 4.94 0.770
Ipsi-Contra Lateral Tilt 9.83 10.20 65.57 0.28 10.49 11.56 62.98 0.05 0.474
Contra-Ipsi Lateral Rotation 12.25 8.51 50.01 0.67 11.88 8.95 59.82 0.29 0.602
Hip Flexion-Extension 7.98 10.13 65.29 0.15 8.18 8.86 60.56 0.33 0.787
Adduction-Abduction 15.39 15.10 66.67 0.84 16.40 14.69 66.62 1.59 0.372
Internal-External Rotation 28.46 15.05 66.06 3.25 29.51 13.59 63.38 5.99 0.164
Knee Flexion-Extension 6.62 6.64 61.39 0.63 7.71 6.19 62.62 0.40 0.045
Adduction-Abduction 29.80 16.00 66.05 2.38 30.33 13.42 63.55 2.61 0.545
Internal-External Rotation 30.06 13.17 62.85 6.59 27.71 12.44 62.08 4.34 0.009
Ankle Dorsi-Plantar Flexion 11.77 9.08 66.67 0.64 10.91 7.88 58.57 1.045 0.294
Eversion-Inversion 21.22 10.39 57.16 1.87 22.97 11.76 63.11 1.98 0.036
Internal-External Rotation 30.00 14.85 66.61 1.17 31.13 14.18 66.67 1.22 0.261
Abbreviations: SD, standard deviation; Max, maximum; Min, minimum.
Line 360-366:
It has been reported that the walking speed affects individuals’ gait kinematics [39,
40]; however, the influence of treadmill walking speed on gait symmetry kinematics
in healthy individuals remains unclear. Even though it has been reported that the
imposed constant speed of a treadmill may artificially impose motor control of gait
and impede the natural variation that occurs during overground walking and therefore
minimize gait variability [41, 42], overall, our findings suggest that young healthy
adults may be more asymmetrical during fast treadmill walking than normal treadmill
walking (see Table 3).
• Line 318-19: There exist some studies analyzing gait symmetry of healthy participants,
for example:
o Cimolin V, Cau N, Sartorio A, et al. Symmetry of Gait in Underweight, Normal and
Overweight Children and Adolescents. Sensors (Basel) 2019; 19:9; doi:10.3390/s19092054.
o Nigg S, Vienneau J, Maurer C, Nigg BM. Development of a symmetry index using discrete
variables. Gait Posture 2013; 38:1; doi:10.1016/j.gaitpost.2012.10.024.
o Queen R, Dickerson L, Ranganathan S, Schmitt D. A novel method for measuring asymmetry
in kinematic and kinetic variables: The normalized symmetry index. J Biomech 2020;
99; doi:10.1016/j.jbiomech.2019.109531.
o Gouwanda D. Further validation of Normalized Symmetry Index and normalized cross-correlation
in identifying gait asymmetry on restricted knee and ankle movement. IEEE-EMBS Conference
on Biomedical Engineering and Sciences 2012; doi:10.1109/IECBES.2012.6498167.
o Herzog W, Nigg BM, Read LJ, Olsson E. Asymmetries in ground reaction force patterns
in normal human gait. Med Sci Sports Exerc 1989; 21:1; doi:10.1249/00005768-198902000-00020.
o Gouwanda D, Senanayake SMNA. Identifying gait asymmetry using gyroscopes--a cross-correlation
and Normalized Symmetry Index approach. J Biomech 2011; 44:5; doi:10.1016/j.jbiomech.2010.12.013.
o Gouwanda D, Senanayake SMNA. Periodical gait asymmetry assessment using real-time
wireless gyroscopes gait monitoring system. J Med Eng Technol 2011; 35:8; doi:10.3109/03091902.2011.627080.
o Xu Y, Hou Q, Wang C, Simpson T, Bennett B, Russell S. How Well Can Modern Nonhabitual
Barefoot Youth Adapt to Barefoot and Minimalist Barefoot Technology Shoe Walking,
in regard to Gait Symmetry. Biomed Res Int 2017; 2017; doi:10.1155/2017/4316821.
o Siebers, HL, Alrawashdeh, W, Migliorini, F, Hildebrand, F, Betsch, M, Eschweiler,
J, Comparison of different symmetry indices for the quantification of dynamic joint
angles. BMC Sports Science, Medicine and Rehabilitation, 2021.
o Alrawashdeh, W, Siebers, HL, Reim, J, Rath, B, Tingart, M, Eschweiler, J, Gait symmetry
– A valid parameter for pre and post planning for total knee arthroplasty. Journal
of Musculoskeletal and Neuronal Interactions, 2021.
Reply: We and thank the Reviewer for the insightful comment. The suggested studies
have been referenced and discussed accordingly in order to increase the clarity for
readership.
Line 374-393:
Previous studies have investigated spine and lower body gait kinematics [6, 8, 9,
24-27]. In addition, although several studies have investigated on gait symmetry [17-23,
45] and presented valuable information, there is not generally accepted standard for
characterization of gait symmetry [23]. Asymmetric gait patterns in healthy individuals
may be expected as there exist natural functional differences between the lower extremities
[12, 41, 43], such as the contribution of each limb in carrying out the tasks of propulsion
and control during able-bodied walking [43]. The present study provides information
not only on the degree of asymmetry, the mean angular difference between left and
right sides, but also on the SInorm in healthy individuals during normal and fast
treadmill walking. Such information will add to the knowledge provided by previous
investigations to better understand spine, pelvis, and lower body motions in healthy
individuals. Our findings on SInorm for lower body motions in the sagittal plane were
comparable to the ones described in [23]. Moreover, this study adds information on
the SInorm parameter by describing the spine and pelvis 3D angular motions. In addition,
reference degree of asymmetry information in healthy individuals has been presented
in this study to help in the biomechanical assessment pathological individuals. Although
the use of this indicator may be confusing as it is not referenced to the joint range
of motion, such indicator has been implemented to assess asymmetry in pathological
individuals. For instance, the degrees of asymmetry reported in total hip [16, 28,
29] and knee [15] replacement patients are greater than the degrees of asymmetry observed
in the present study. Consequently, degrees of asymmetry greater than the ones reported
in this study may be an indicative of abnormal gait function.
• Line 324-26: The argument was already presented in the introduction.
Reply: We agree and thank the Reviewer for the comment. The argument has been removed
from the Discussion Section.
• In Figure 1 different participants were shown, with different shoes. The influence
of different shoes was not mentioned in the limitation section.
Reply: We agree and thank the Reviewer for the comment. We have included in the Limitations
Section that the influence of different shoes on gait symmetry was not investigated.
Line 399-401:
Additionally, participants wore different types of shoes during the experiments; thus,
the influence of distinct shoes was not investigated in this study.
Overall:
• The ‘degree of asymmetry’ is presented in degree and described as a mean difference
between left and right side movements. Comparing this degree of asymmetry between
different motions is difficult, as it should be interpreted in combination with the
range of motion. 3° difference is a lot in case of a range of motion of 10° for posterior-anterior
pelvic tilt. In contrast in the case of an 80° range of motion for knee flexion-extension,
a 3° difference is negligible.
Reply: We agree and thank the Reviewer for the insightful comment. Even though the
degree of asymmetry is not referenced to the different range of motions of different
movements, it is a parameter that has been reported in the literature, for example:
1. Arauz P, Peng Y, Kwon Y-M. Knee motion symmetry was not restored in patients with
unilateral bi-cruciate retaining total knee arthroplasty—in vivo three-dimensional
kinematic analysis. International orthopaedics 42(12): 2817, 2018
2. Arauz P, Peng Y, MacAuliffe J, Kwon Y-M. In-vivo 3-Dimensional gait symmetry analysis
in patients with bilateral total hip arthroplasty. Journal of biomechanics 77: 131,
2018
3. Tsai T-Y, Dimitriou D, Li J-S, Woo Nam K, Li G, Kwon Y-M. Asymmetric hip kinematics
during gait in patients with unilateral total hip arthroplasty: In vivo 3-dimensional
motion analysis. Journal of Biomechanics 48(4): 555, 2015
Nevertheless, in order to increase clarity for readership, in addition to the degree
of asymmetry, the normalized symmetry index has been calculated and discussed accordingly.
Figures 3, 4, 5, and 6, as well as Tables 1 and 2 have been revised accordingly. Likewise,
Table 3, describing the result of the normalized symmetry index has been included.
Line 242-245:
Descriptive statistics of the average degree of asymmetry, describing the mean difference
between left and right-side movements when the scalar field SPM detected significant
differences, and the maximum magnitude of the SInorm when the scalar field SPM detected
significant differences, in spine segments during normal and fast treadmill walking
are presented in Table 1.
Line 321-325:
Descriptive statistics of the average degree of asymmetry, describing the mean difference
between Descriptive statistics of the average degree of asymmetry, describing the
mean difference between left and right-side movements when the scalar field SPM detected
significant differences, and the maximum magnitude of the SInorm when the scalar field
SPM detected significant differences, in the pelvis segment and lower body joints
during normal and fast treadmill walking are presented in Table 2.
Line 333-335:
Descriptive statistics of the SInorm and its comparison between normal and fast treadmill
walking is presented in Table 3. Overall, greater asymmetries were found during fast
treadmill walking than normal treadmill walking.
Figures:
• A grid in the graphs could be helpful.
Reply: We agree and thank the Reviewer for the comment. Several figures were revised.
At the end, a grid was not included because figure information was clear enough.
Figure 4:
• It is not necessary to mention a complex description two times, in the manuscript
and the figure heading.
Reply: We thank the Reviewer for the comment. Figure descriptions have been revised
in the Results Section accordingly in order to increase the clarity for readership.
• Figures 5 & 6: For hip, knee, and ankle flexion-extension the standard deviation
of the left side is much higher than from the right side, which should be mentioned
and discussed.
Reply: We agree and thank the Reviewer for the insightful comment. We have made clear
that the standard deviation of the left side is higher than from the right side in
the Results and Discussion Sections accordingly in order to increase clarity for readership.
Line 275-276:
The standard deviation of the left side was higher than the right side for hip, knee,
and ankle motions (Fig. 5).
Line 306-307:
The standard deviation of the left side was higher than the right side for hip, knee,
and ankle motions (Fig. 6).
Line 366-372:
In addition, our results revealed standard deviations of the left side higher than
the right side for hip, knee, and ankle motions during normal and treadmill walking.
A possible explanation for this difference may be related to laterality [43], as in
our study, 52 out 60 participants reported to be right-dominant, with leg dominance
being defined as the preferred leg for kicking a ball. These results disagree with
previous reports indicating that walking slowly is more challenging to the motor control
of gait than usual and faster speed walks [41, 44].
Reviewer #2
Reviewer #2: Major comment:
While the manuscript is, in my opinion, generally well-written, and methodology does
not pose any major problems, I think the discussion section needs to include much
more detail on the interpretation of the results. There are a number of significant
differences found between L/R sides for very subtle values of asymmetry, and I question
what the real-life impact these values have or represent. Is a difference of <0.5
degrees noticeable? What does this mean for a healthy individual?
Reply: We agree and thank the Reviewer for the insightful comments. We have revised
the Discussion Section in order to provide more details on the interpretation of the
results.
In addition to the degree of asymmetry, the normalized symmetry index has been calculated
and discussed accordingly in order to increase the clarity for readership. Figures
3, 4, 5, and 6, as well as Tables 1 and 2 have been revised accordingly. Likewise,
Table 3, describing the result of the normalized symmetry index has been included.
Even though the degree of asymmetry is not referenced to the different range of motions
of different movements, it is a parameter that has been reported in the literature,
for example:
1. Arauz P, Peng Y, Kwon Y-M. Knee motion symmetry was not restored in patients with
unilateral bi-cruciate retaining total knee arthroplasty—in vivo three-dimensional
kinematic analysis. International orthopaedics 42(12): 2817, 2018
2. Arauz P, Peng Y, MacAuliffe J, Kwon Y-M. In-vivo 3-Dimensional gait symmetry analysis
in patients with bilateral total hip arthroplasty. Journal of biomechanics 77: 131,
2018
3. Tsai T-Y, Dimitriou D, Li J-S, Woo Nam K, Li G, Kwon Y-M. Asymmetric hip kinematics
during gait in patients with unilateral total hip arthroplasty: In vivo 3-dimensional
motion analysis. Journal of Biomechanics 48(4): 555, 2015
Furthermore, the information from the normalized symmetry index has been used to statistically
analyze the differences between normal and fast treadmill walking.
The degree of asymmetry and the normalized symmetry index have been described and
discussed accordingly to make the paper clearer.
The symmetry parameters presented in this study can be used as reference information
to help to guide clinical decision-making.
Line 170-174:
Symmetry was calculated throughout the gait cycle for spine, pelvis, and lower body
motions. Statistical parametric mapping and the normalized symmetry index, presented
by Gouwanda et al. [21], were calculated for assessing gait symmetry of the spine
and pelvis angular motions, as well as lower body joint angles. The normalized symmetry
index (SInorm) was calculated based on Eq. 1 [19-21, 23].
Line 333-342:
Descriptive statistics of the SInorm and its comparison between normal and fast treadmill
walking is presented in Table 3. Overall, greater asymmetries were found during fast
treadmill walking than normal treadmill walking.
Table 3. Descriptive statistics of the maximum SInorm in % and its comparison between
normal and fast treadmill walking for N=60 participants.
Segment Motion Treadmill Walking Normal Treadmill Walking Fast
Mean SD Max Min Mean SD Max Min p-value
Upper Thorax Posterior-Anterior Tilt 45.56 12.47 66.67 12.70 44.17 12.61 65.61 12.64
0.201
Ipsi-Contra Lateral Tilt 13.87 11.07 60.71 0.56 15.36 12.07 63.82 0.84 0.109
Contra-Ipsi Lateral Rotation 22.28 14.08 64.70 0.81 22.59 12.30 58.93 1.28 0.765
Lower Thorax Posterior-Anterior Tilt 44.88 11.76 66.50 15.60 42.42 11.28 65.84 9.50
0.019
Ipsi-Contra Lateral Tilt 15.11 11.30 56.47 0.46 17.82 12.17 59.03 0.00 0.000
Contra-Ipsi Lateral Rotation 13.60 9.13 60.25 2.03 13.69 10.75 66.07 0.54 0.919
Upper Lumbar Posterior-Anterior Tilt 42.05 11.84 66.67 9.69 41.35 11.09 66.67 16.63
0.422
Ipsi-Contra Lateral Tilt 13.77 10.86 64.38 0.00 13.65 10.10 59.13 0.18 0.867
Contra-Ipsi Lateral Rotation 10.87 8.21 64.26 1.05 11.42 9.24 66.67 0.41 0.456
Lower Lumbar Posterior-Anterior Tilt 37.29 12.85 66.67 11.15 37.79 12.95 66.67 12.54
0.574
Ipsi-Contra Lateral Tilt 14.82 10.16 55.32 0.00 15.90 11.83 59.77 0.59 0.163
Contra-Ipsi Lateral Rotation 14.51 9.99 56.92 0.05 16.82 11.77 63.86 0.75 0.002
Pelvis Posterior-Anterior Tilt 38.10 14.02 66.67 6.40 37.77 13.83 66.67 4.94 0.770
Ipsi-Contra Lateral Tilt 9.83 10.20 65.57 0.28 10.49 11.56 62.98 0.05 0.474
Contra-Ipsi Lateral Rotation 12.25 8.51 50.01 0.67 11.88 8.95 59.82 0.29 0.602
Hip Flexion-Extension 7.98 10.13 65.29 0.15 8.18 8.86 60.56 0.33 0.787
Adduction-Abduction 15.39 15.10 66.67 0.84 16.40 14.69 66.62 1.59 0.372
Internal-External Rotation 28.46 15.05 66.06 3.25 29.51 13.59 63.38 5.99 0.164
Knee Flexion-Extension 6.62 6.64 61.39 0.63 7.71 6.19 62.62 0.40 0.045
Adduction-Abduction 29.80 16.00 66.05 2.38 30.33 13.42 63.55 2.61 0.545
Internal-External Rotation 30.06 13.17 62.85 6.59 27.71 12.44 62.08 4.34 0.009
Ankle Dorsi-Plantar Flexion 11.77 9.08 66.67 0.64 10.91 7.88 58.57 1.045 0.294
Eversion-Inversion 21.22 10.39 57.16 1.87 22.97 11.76 63.11 1.98 0.036
Internal-External Rotation 30.00 14.85 66.61 1.17 31.13 14.18 66.67 1.22 0.261
Abbreviations: SD, standard deviation; Max, maximum; Min, minimum.
Line 374-394:
Previous studies have investigated spine and lower body gait kinematics [6, 8, 9,
24-27]. In addition, although several studies have investigated on gait symmetry [17-23,
45] and presented valuable information, there is not generally accepted standard for
characterization of gait symmetry [23]. Asymmetric gait patterns in healthy individuals
may be expected as there exist natural functional differences between the lower extremities
[12, 41, 43], such as the contribution of each limb in carrying out the tasks of propulsion
and control during able-bodied walking [43]. The present study provides information
not only on the degree of asymmetry, the mean angular difference between left and
right sides, but also on the SInorm in healthy individuals during normal and fast
treadmill walking. Such information will add to the knowledge provided by previous
investigations to better understand spine, pelvis, and lower body motions in healthy
individuals. Our findings on SInorm for lower body motions in the sagittal plane were
comparable to the ones described in [23]. Moreover, this study adds information on
the SInorm parameter by describing the spine and pelvis 3D angular motions. In addition,
reference degree of asymmetry information in healthy individuals has been presented
in this study to help in the biomechanical assessment pathological individuals. Although
the use of this indicator may be confusing as it is not referenced to the joint range
of motion, such indicator has been implemented to assess asymmetry in pathological
individuals. For instance, the degrees of asymmetry reported in total hip [16, 28,
29] and knee [15] replacement patients are greater than the degrees of asymmetry observed
in the present study. Consequently, degrees of asymmetry greater than the ones reported
in this study may be an indicative of abnormal gait function.
Specific comments:
Line 36 – ‘compared for treadmill walking’ – suggest adding in detail about normal
and fast speeds
Reply: We agree and thank the Reviewer for the comment. The sentence has been revised
in the Abstract accordingly in order to increase clarity for readership.
Line 36-38:
The spine and pelvis angular motions associated with the left and right lower limb
motions, as well as the left and right lower extremity joint angles were compared
for normal and fast treadmill walking
Line 67 – ‘common in clinical and rehabilitation practices’ – yes, sure, but these
would be for injured or clinical populations, so why not just use overground walking
for your healthy adults in this study? Or both overground and treadmill walking?
Reply: We agree and thank the Reviewer for the comment. The goal of this study is
to provide reference information on symmetry using healthy individuals, so it can
be used for treating injured and clinical populations. Therefore, in this study, we
used treadmill walking to generate such reference information as treadmills are commonly
used in clinical and rehabilitation practices.
Line 75-78:
Walking overground is more natural than walking on a treadmill [30-32]. However, the
use of treadmills is very common in clinical and rehabilitation practices as they
allow for smaller space, better control of walking speeds, and a more controlled environment
for kinematics and kinetic studies [32, 33].
Line 73 – this hypothesis seems to be worded as if it is the null hypothesis?
Reply: We agree and thank the Reviewer for the comment. The sentence has been revised
in the Introduction Section accordingly in order to increase clarity for readership.
Line 84-88:
We hypothesized that there are significant differences between the spine and pelvis
angular movements associated with the left lower limb motions and spine and pelvis
angular movements associated with the right lower limb motions, as well as between
the left and right lower extremity joint angles during normal and fast treadmill walking
in healthy individuals.
Line 82 – what is meant by ‘right-leg dominant’? How was leg dominance defined? Is
this relevant here?
Reply: We thank the Reviewer for the comment. Leg dominance was defined as the preferred
leg for kicking a ball. We have made clear in the Methods Section that fifty-two participants
reported to be right-dominant. This has been included as a study limitation as no
action was taken to control the dominant leg during the experiment.
Line 94-95:
Fifty-two out of the sixty participants reported to be right-leg dominant (with leg
dominance being defined as the preferred leg for kicking a ball).
Line 394-397:
limitations need to be considered to interpret the present results. To begin with,
the average age of the male and female participants in this study was ~21 years old,
52 out of 60 participants reported to be right-dominant, and all participants reported
a healthy lifestyle (exercised at least twice a week); hence, results may be limited
to similar populations.
Line 91-93 – I’m assuming the walking speeds were determined in separate trials (e.g.
4 x regular; 4 x fast) and not a within-trial acceleration?
Reply: We thank the Reviewer for the comment. Yes, the walking speeds were determined
in separate trials. We have made this clear in the Methods Section in order to increase
the clarity for readership.
Line 103-107:
All participants first executed normal and fast level overground walking over a distance
of 5 m for 4 times in separate trials. Participants were instructed to sustain a usual
regular pace during normal overground walking, and accelerate their usual regular
pace (as if they were in a hurry) during fast overground walking. The walking speeds
of both conditions were recorded and used to set up the treadmill speeds.
Line 113 – ‘z axes’ – it would be helpful to state explicitly which direction this
is (vertical)
Reply: We thank the Reviewer for the comment. Although the z-axes mostly point in
the vertical direction during standing and treadmill walking, those axes are the local
axes attached to spine segments. Therefore, they are not exactly in the vertical direction
as they change with participants’ anatomy and motion.
Line 126-130 – were kinematics filtered at all?
Reply: We thank the Reviewer for the comment. Although no filter was applied to the
raw data, all kinematics data were indirectly filtered, as the average of at least
30 complete cycles was used for analysis.
Line 113-116:
Each participant performed three trials that included at least ten complete gait cycles
at normal and fast walking speeds. Thus, in total, each test condition had at least
30 complete gait cycles, and those were selected for analyses.
Statistical analyses – (i) It appears that males and females were combined. Would
there be reason to separate these two groups to evaluate for sex-based characteristics/differences?
(ii) Why weren’t statistical analyses included to compare the treadmill walking speeds?
Reply: We thank the Reviewer for the comment. It is possible to analyze sex-based
characteristics/differences. However, the present study has mainly focused on the
analysis of gait symmetry for males and females together.
Furthermore, the information from the normalized symmetry index has been introduced
to statistically analyze the differences between normal and fast treadmill walking.
Line 333-335:
Descriptive statistics of the SInorm and its comparison between normal and fast treadmill
walking is presented in Table 3. Overall, greater asymmetries were found during fast
treadmill walking than normal treadmill walking.
Table 3. Descriptive statistics of the maximum SInorm in % and its comparison between
normal and fast treadmill walking for N=60 participants.
Segment Motion Treadmill Walking Normal Treadmill Walking Fast
Mean SD Max Min Mean SD Max Min p-value
Upper Thorax Posterior-Anterior Tilt 45.56 12.47 66.67 12.70 44.17 12.61 65.61 12.64
0.201
Ipsi-Contra Lateral Tilt 13.87 11.07 60.71 0.56 15.36 12.07 63.82 0.84 0.109
Contra-Ipsi Lateral Rotation 22.28 14.08 64.70 0.81 22.59 12.30 58.93 1.28 0.765
Lower Thorax Posterior-Anterior Tilt 44.88 11.76 66.50 15.60 42.42 11.28 65.84 9.50
0.019
Ipsi-Contra Lateral Tilt 15.11 11.30 56.47 0.46 17.82 12.17 59.03 0.00 0.000
Contra-Ipsi Lateral Rotation 13.60 9.13 60.25 2.03 13.69 10.75 66.07 0.54 0.919
Upper Lumbar Posterior-Anterior Tilt 42.05 11.84 66.67 9.69 41.35 11.09 66.67 16.63
0.422
Ipsi-Contra Lateral Tilt 13.77 10.86 64.38 0.00 13.65 10.10 59.13 0.18 0.867
Contra-Ipsi Lateral Rotation 10.87 8.21 64.26 1.05 11.42 9.24 66.67 0.41 0.456
Lower Lumbar Posterior-Anterior Tilt 37.29 12.85 66.67 11.15 37.79 12.95 66.67 12.54
0.574
Ipsi-Contra Lateral Tilt 14.82 10.16 55.32 0.00 15.90 11.83 59.77 0.59 0.163
Contra-Ipsi Lateral Rotation 14.51 9.99 56.92 0.05 16.82 11.77 63.86 0.75 0.002
Pelvis Posterior-Anterior Tilt 38.10 14.02 66.67 6.40 37.77 13.83 66.67 4.94 0.770
Ipsi-Contra Lateral Tilt 9.83 10.20 65.57 0.28 10.49 11.56 62.98 0.05 0.474
Contra-Ipsi Lateral Rotation 12.25 8.51 50.01 0.67 11.88 8.95 59.82 0.29 0.602
Hip Flexion-Extension 7.98 10.13 65.29 0.15 8.18 8.86 60.56 0.33 0.787
Adduction-Abduction 15.39 15.10 66.67 0.84 16.40 14.69 66.62 1.59 0.372
Internal-External Rotation 28.46 15.05 66.06 3.25 29.51 13.59 63.38 5.99 0.164
Knee Flexion-Extension 6.62 6.64 61.39 0.63 7.71 6.19 62.62 0.40 0.045
Adduction-Abduction 29.80 16.00 66.05 2.38 30.33 13.42 63.55 2.61 0.545
Internal-External Rotation 30.06 13.17 62.85 6.59 27.71 12.44 62.08 4.34 0.009
Ankle Dorsi-Plantar Flexion 11.77 9.08 66.67 0.64 10.91 7.88 58.57 1.045 0.294
Eversion-Inversion 21.22 10.39 57.16 1.87 22.97 11.76 63.11 1.98 0.036
Internal-External Rotation 30.00 14.85 66.61 1.17 31.13 14.18 66.67 1.22 0.261
Abbreviations: SD, standard deviation; Max, maximum; Min, minimum.
Line 171 – the values reported here (and throughout the rest of the results section)
for detected degrees of asymmetry are extremely small (e.g. posterior tilt 0.46+/-
0.03 degree) and in many cases for a very short period of time (e.g. lower lumbar
p/a tilt at normal speed – 2-3% gait cycle). Could they be prone to marker placement
error? Or artefacts from the SPM analysis (e.g. as a result of temporal shifting –
I don’t think this is the case, but more details on how SPM was performed in the methods
section might also help)? With that in mind, are these results meaningful?
Reply: We agree and thank the Reviewer for the comment. The degree of asymmetry is
small as it is not referenced to the different ranges of motions of different movements.
Yet, it is a parameter that has been reported in the literature. In addition to the
degree of asymmetry, the normalized symmetry index has been calculated and discussed
accordingly in order to increase the clarity for readership.
Small variations may not be prone to marker placement error as one experienced researcher
consistently placed the markers on the bony anatomical landmarks of all participants
in this study.
More details on SPM analysis have been introduced accordingly in the Results Section
in order to increase the clarity for readership. The Results Section has been revised
and the SPM threshold has been included accordingly. The SPM threshold is calculated
automatically by using the SPM 1D function in MATALB. The threshold value must be
exceeded to detect significant differences. Fig. 4 illustrates examples of thresholds
t* for different motions.
The degree of asymmetry and the normalized symmetry index have been reported in the
literature. Thus, we have included and discussed this information in order to make
the paper clearer.
Line 124-128:
Average and standard deviation of upper thorax, lower thorax, upper lumbar, and lower
lumbar posterior-anterior (P/A) tilt, ipsi-contralateral (Ipsi/Con) tilt, and contra-ipsi
(Con/Ipsi) rotation, for left and right sides during one gait cycle of fast treadmill
walking (TWF) in sixty healthy participants. Green bars on the horizontal axis and
the scalar field SPM results with threshold t* depict where, in % cycle, left side
angles were greater or lesser than right side angles. The normalized symmetry index
(SInorm) calculated during one gait cycle of TWF. Solid and dashed lines correspond
to average left and right sides, as well as average SInorm, and shaded areas correspond
to standard deviation. Black dotted vertical lines denote toe-off.
Figure 4:
Line 242-245:
Descriptive statistics of the average degree of asymmetry, describing the mean difference
between left and right-side movements when the scalar field SPM detected significant
differences, and the maximum magnitude of the SInorm when the scalar field SPM detected
significant differences, in spine segments during normal and fast treadmill walking
are presented in Table 1.
Line 321-325
Descriptive statistics of the average degree of asymmetry, describing the mean difference
between left and right-side movements when the scalar field SPM detected significant
differences, and the maximum magnitude of the SInorm when the scalar field SPM detected
significant differences, in the pelvis segment and lower body joints during normal
and fast treadmill walking are presented in Table 2.
Line 333-335:
Descriptive statistics of the SInorm and its comparison between normal and fast treadmill
walking is presented in Table 3. Overall, greater asymmetries were found during fast
treadmill walking than normal treadmill walking.
Line 374-394:
Previous studies have investigated spine and lower body gait kinematics [6, 8, 9,
24-27]. In addition, although several studies have investigated on gait symmetry [17-23,
45] and presented valuable information, there is not generally accepted standard for
characterization of gait symmetry [23]. Asymmetric gait patterns in healthy individuals
may be expected as there exist natural functional differences between the lower extremities
[12, 41, 43], such as the contribution of each limb in carrying out the tasks of propulsion
and control during able-bodied walking [43]. The present study provides information
not only on the degree of asymmetry, the mean angular difference between left and
right sides, but also on the SInorm in healthy individuals during normal and fast
treadmill walking. Such information will add to the knowledge provided by previous
investigations to better understand spine, pelvis, and lower body motions in healthy
individuals. Our findings on SInorm for lower body motions in the sagittal plane were
comparable to the ones described in [23]. Moreover, this study adds information on
the SInorm parameter by describing the spine and pelvis 3D angular motions. In addition,
reference degree of asymmetry information in healthy individuals has been presented
in this study to help in the biomechanical assessment pathological individuals. Although
the use of this indicator may be confusing as it is not referenced to the joint range
of motion, such indicator has been implemented to assess asymmetry in pathological
individuals. For instance, the degrees of asymmetry reported in total hip [16, 28,
29] and knee [15] replacement patients are greater than the degrees of asymmetry observed
in the present study. Consequently, degrees of asymmetry greater than the ones reported
in this study may be an indicative of abnormal gait function.
Line 300 – ‘internal notation’ – I think this is meant to be ‘rotation’?
Reply: We agree and thank the Reviewer for the comment. The sentence has been revised
in the Introduction and Discussion Sections accordingly in order to increase clarity
for readership.
Line 349-352:
Degrees of asymmetry and the associated maximum magnitude of SInorm of 5.74±0.04°
and 14%, as well as 5.33±0.18° and 21%, for the lower lumbar contra-ipsi lateral rotation
and hip internal rotation, respectively, were the largest asymmetries detected during
normal treadmill walking.
Line 305 – links to comment above regarding hypothesis – this statement seems to conflict
with the way the hypothesis was worded (original hypothesis suggests there would not
be any differences, but you have found some, so null hypothesis (that there would
be differences) is, at least, partially supported here).
Reply: We agree and thank the Reviewer for the comment. The sentence has been revised
in the Introduction Section accordingly in order to increase clarity for readership.
Line 84-88:
We hypothesized that there are significant differences between the spine and pelvis
angular movements associated with the left lower limb motions and spine and pelvis
angular movements associated with the right lower limb motions, as well as between
the left and right lower extremity joint angles during normal and fast treadmill walking
in healthy individuals.
Line 357-359:
These results rejected the null hypothesis of no difference in spine, pelvis, and
lower body motions between left and right sides during normal and fast treadmill walking
in healthy individuals.
Line 312 – again, why didn’t you make these comparisons (i.e. through statistical
testing)?
Reply: We thank the Reviewer for the comment. The information from the normalized
symmetry index has been introduced to statistically analyze the differences between
normal and fast treadmill walking. This has been discussed accordingly in order to
increase the clarity for readership.
Line 333-335:
Descriptive statistics of the SInorm and its comparison between normal and fast treadmill
walking is presented in Table 3. Overall, greater asymmetries were found during fast
treadmill walking than normal treadmill walking.
Table 3. Descriptive statistics of the maximum SInorm in % and its comparison between
normal and fast treadmill walking for N=60 participants.
Segment Motion Treadmill Walking Normal Treadmill Walking Fast
Mean SD Max Min Mean SD Max Min p-value
Upper Thorax Posterior-Anterior Tilt 45.56 12.47 66.67 12.70 44.17 12.61 65.61 12.64
0.201
Ipsi-Contra Lateral Tilt 13.87 11.07 60.71 0.56 15.36 12.07 63.82 0.84 0.109
Contra-Ipsi Lateral Rotation 22.28 14.08 64.70 0.81 22.59 12.30 58.93 1.28 0.765
Lower Thorax Posterior-Anterior Tilt 44.88 11.76 66.50 15.60 42.42 11.28 65.84 9.50
0.019
Ipsi-Contra Lateral Tilt 15.11 11.30 56.47 0.46 17.82 12.17 59.03 0.00 0.000
Contra-Ipsi Lateral Rotation 13.60 9.13 60.25 2.03 13.69 10.75 66.07 0.54 0.919
Upper Lumbar Posterior-Anterior Tilt 42.05 11.84 66.67 9.69 41.35 11.09 66.67 16.63
0.422
Ipsi-Contra Lateral Tilt 13.77 10.86 64.38 0.00 13.65 10.10 59.13 0.18 0.867
Contra-Ipsi Lateral Rotation 10.87 8.21 64.26 1.05 11.42 9.24 66.67 0.41 0.456
Lower Lumbar Posterior-Anterior Tilt 37.29 12.85 66.67 11.15 37.79 12.95 66.67 12.54
0.574
Ipsi-Contra Lateral Tilt 14.82 10.16 55.32 0.00 15.90 11.83 59.77 0.59 0.163
Contra-Ipsi Lateral Rotation 14.51 9.99 56.92 0.05 16.82 11.77 63.86 0.75 0.002
Pelvis Posterior-Anterior Tilt 38.10 14.02 66.67 6.40 37.77 13.83 66.67 4.94 0.770
Ipsi-Contra Lateral Tilt 9.83 10.20 65.57 0.28 10.49 11.56 62.98 0.05 0.474
Contra-Ipsi Lateral Rotation 12.25 8.51 50.01 0.67 11.88 8.95 59.82 0.29 0.602
Hip Flexion-Extension 7.98 10.13 65.29 0.15 8.18 8.86 60.56 0.33 0.787
Adduction-Abduction 15.39 15.10 66.67 0.84 16.40 14.69 66.62 1.59 0.372
Internal-External Rotation 28.46 15.05 66.06 3.25 29.51 13.59 63.38 5.99 0.164
Knee Flexion-Extension 6.62 6.64 61.39 0.63 7.71 6.19 62.62 0.40 0.045
Adduction-Abduction 29.80 16.00 66.05 2.38 30.33 13.42 63.55 2.61 0.545
Internal-External Rotation 30.06 13.17 62.85 6.59 27.71 12.44 62.08 4.34 0.009
Ankle Dorsi-Plantar Flexion 11.77 9.08 66.67 0.64 10.91 7.88 58.57 1.045 0.294
Eversion-Inversion 21.22 10.39 57.16 1.87 22.97 11.76 63.11 1.98 0.036
Internal-External Rotation 30.00 14.85 66.61 1.17 31.13 14.18 66.67 1.22 0.261
Abbreviations: SD, standard deviation; Max, maximum; Min, minimum.
Line 67-74:
Furthermore, a classical
Line 321 – some examples of the differences to which you refer here would be helpful
Reply: We thank the Reviewer for the comment. Examples of the natural functional differences
between the lower extremities has been included to make the paper clearer.
Line 360-366:
It has been reported that the walking speed affects individuals’ gait kinematics [39,
40]; however, the influence of treadmill walking speed on gait symmetry kinematics
in healthy individuals remains unclear. Even though it has been reported that the
imposed constant speed of a treadmill may artificially impose motor control of gait
and impede the natural variation that occurs during overground walking and therefore
minimize gait variability [41, 42], overall, our findings suggest that young healthy
adults may be more asymmetrical during fast treadmill walking than normal treadmill
walking (see Table 3).
Line 333 – the wording of this limitation isn’t clear to me; what do you mean by ‘few
gait cycles with repetitions’?
Reply: We thank the Reviewer for the comment. We have clarified in the Limitations
Section that few gait cycles (~30) were used for were used in normal and fast treadmill
walking conditions.
Line 398-399:
Furthermore, few gait cycles (~30) were used in normal and fast treadmill walking
conditions; hence, the long terms of gait asymmetry kinematics were not explored.
Line 345 – again, you didn’t run any tests so I think this statement needs to address
that.
Reply: We thank the Reviewer for the comment. The information from the normalized
symmetry index has been introduced to statistically analyze the differences between
normal and fast treadmill walking. This has been discussed accordingly in order to
increase the clarity for readership.
Line 67-74:
Furthermore, a classical
Line 347 – as per my main comment with the discussion section, a summary statement
of the significance of these very small degrees of asymmetry should be included. What
is the take-home message/impact of these findings?
Reply: We agree and thank the Reviewer for the comment. The degree of asymmetry is
small as it is not referenced to the different range of motions of different movements.
Yet, it is a parameter that has been reported in the literature. In addition to the
degree of asymmetry, the normalized symmetry index has been calculated and discussed
accordingly in order to increase the clarity for readership.
Line 333-335:
Descriptive statistics of the SInorm and its comparison between normal and fast treadmill
walking is presented in Table 3. Overall, greater asymmetries were found during fast
treadmill walking than normal treadmill walking.
Table 3. Descriptive statistics of the maximum SInorm in % and its comparison between
normal and fast treadmill walking for N=60 participants.
Segment Motion Treadmill Walking Normal Treadmill Walking Fast
Mean SD Max Min Mean SD Max Min p-value
Upper Thorax Posterior-Anterior Tilt 45.56 12.47 66.67 12.70 44.17 12.61 65.61 12.64
0.201
Ipsi-Contra Lateral Tilt 13.87 11.07 60.71 0.56 15.36 12.07 63.82 0.84 0.109
Contra-Ipsi Lateral Rotation 22.28 14.08 64.70 0.81 22.59 12.30 58.93 1.28 0.765
Lower Thorax Posterior-Anterior Tilt 44.88 11.76 66.50 15.60 42.42 11.28 65.84 9.50
0.019
Ipsi-Contra Lateral Tilt 15.11 11.30 56.47 0.46 17.82 12.17 59.03 0.00 0.000
Contra-Ipsi Lateral Rotation 13.60 9.13 60.25 2.03 13.69 10.75 66.07 0.54 0.919
Upper Lumbar Posterior-Anterior Tilt 42.05 11.84 66.67 9.69 41.35 11.09 66.67 16.63
0.422
Ipsi-Contra Lateral Tilt 13.77 10.86 64.38 0.00 13.65 10.10 59.13 0.18 0.867
Contra-Ipsi Lateral Rotation 10.87 8.21 64.26 1.05 11.42 9.24 66.67 0.41 0.456
Lower Lumbar Posterior-Anterior Tilt 37.29 12.85 66.67 11.15 37.79 12.95 66.67 12.54
0.574
Ipsi-Contra Lateral Tilt 14.82 10.16 55.32 0.00 15.90 11.83 59.77 0.59 0.163
Contra-Ipsi Lateral Rotation 14.51 9.99 56.92 0.05 16.82 11.77 63.86 0.75 0.002
Pelvis Posterior-Anterior Tilt 38.10 14.02 66.67 6.40 37.77 13.83 66.67 4.94 0.770
Ipsi-Contra Lateral Tilt 9.83 10.20 65.57 0.28 10.49 11.56 62.98 0.05 0.474
Contra-Ipsi Lateral Rotation 12.25 8.51 50.01 0.67 11.88 8.95 59.82 0.29 0.602
Hip Flexion-Extension 7.98 10.13 65.29 0.15 8.18 8.86 60.56 0.33 0.787
Adduction-Abduction 15.39 15.10 66.67 0.84 16.40 14.69 66.62 1.59 0.372
Internal-External Rotation 28.46 15.05 66.06 3.25 29.51 13.59 63.38 5.99 0.164
Knee Flexion-Extension 6.62 6.64 61.39 0.63 7.71 6.19 62.62 0.40 0.045
Adduction-Abduction 29.80 16.00 66.05 2.38 30.33 13.42 63.55 2.61 0.545
Internal-External Rotation 30.06 13.17 62.85 6.59 27.71 12.44 62.08 4.34 0.009
Ankle Dorsi-Plantar Flexion 11.77 9.08 66.67 0.64 10.91 7.88 58.57 1.045 0.294
Eversion-Inversion 21.22 10.39 57.16 1.87 22.97 11.76 63.11 1.98 0.036
Internal-External Rotation 30.00 14.85 66.61 1.17 31.13 14.18 66.67 1.22 0.261
Abbreviations: SD, standard deviation; Max, maximum; Min, minimum.
Line 412-414:
Our findings suggest that young healthy adults may be more asymmetrical during fast
treadmill walking than normal treadmill walking.
Figure 3 – legend for Upper Lumbar P/A tilt has ‘GWN’ which isn’t explained anywhere.
I’m assuming it is ‘ground walking normal’, but might be a typo?
Reply: We thank the Reviewer for the comment. All figures have been revised and corrected
accordingly in order to increase the clarity for readership.
Line 209-216:
Fig 3. Average and standard deviation of upper thorax, lower thorax, upper lumbar,
and lower lumbar posterior-anterior (P/A) tilt, ipsi-contralateral (Ipsi/Con) tilt,
and contra-ipsi (Con/Ipsi) rotation, for left and right sides during one gait cycle
of normal treadmill walking (TWN) in sixty healthy participants. Green bars on the
horizontal axis and the scalar field SPM results with threshold t* depict where, in
% cycle, left side angles were greater or lesser than right side angles. The normalized
symmetry index (SInorm) calculated during one gait cycle of TWN. Solid and dashed
lines correspond to average left and right sides, as well as average SInorm, and shaded
areas correspond to standard deviation. Black dotted vertical lines denote toe-off.
Figure 3:
- Attachments
- Attachment
Submitted filename: Response to Reviewers_PLoS_One_Gait Symmetry TW.docx
https://orcid.org/0000-0002-8724-7035
