Kinematic Analysis of Short and Long Services in Table Tennis

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

 

General comments.

This study explores the comparison of kinematics between short and long serves in table tennis, offering potentially valuable insights for coaches. However, I have several concerns—not regarding the measurements themselves, but rather the presentation and analysis of the data. Moreover, despite the potential interest of this study, I believe it falls outside the scope of this journal. Other journals, such as MDPI Sports, may be more suitable for its publication. Specific comments are provided below:

# Introduction:

L68-69: ok, but what is the interest? Please assist the reader in specifying the added-value to literature.

If the goal is to improve the learning of the technique for these strokes, it is necessary to provide the kinematic curves as a function of time rather than the extreme values. The extreme values are relevant for the physical preparation of athletes and should therefore be correlated with other strokes, as was done by Marsan (for instance), although this area still requires significant development.

Ref Marsan: https://journal.racketsportscience.org/index.php/ijrss/article/view/26

L83-85: In that case, please add curves of kinematics time courses.

L89: “foot tennis” ????

L90: please specify here what is/are the hypothesis (es)

 

# Material and methods

L118: To give readers an idea of the potential impact of fatigue between the two series, please specify an approximate total number of serves required to achieve 10 accurate serves per series.

L132-134: ok but please specify here the references

L134-137: "most studies" and finally only one reference

L150: “0.01% of cycle time” . Instead, use 'task time' as it is not a cyclic movement. Additionally, provide an approximate duration of the task to assess the significance of a 0.01% refinement in task time.

L159-165: If calculated using the 3D identification of Euler-Cardan or Tait-Bryan angles, these angles do not correspond to the frontal plane (as they depend on the flexion/extension angle). For internal/external rotation, with a sequence of Flex/Ext followed by Abd/Add and then IntR/ExtR, the calculated angle is based on the femur’s longitudinal axis, not the pelvis.

Refer to the published paper on the joint coordinate system:
“A Joint Coordinate System for the Clinical Description of Three-Dimensional Motions: Application to the Knee” by Grood and Suntay (1983) - DOI: 10.1115/1.3138397.

L202-207: see above comment. And take care about the angle order in angle identification

L212-219: the same.

L221: reference to [24] seems inappropriate. Rather [25]?  please check all the references call throughout the text

L234: maybe add a paragraph on data processing to specify which quantities/parameters will be extracted: for instance, maximal joint angle, magnitude, etc. Also include if maximal values (or mean or median) were extracted from each "cycles" then average or from an average "cycle"

L237: please specify the selected level of statistical significance here

 

# Results

L239-242: move into “statistical analysis”, ie the previous paragraph?

All tables: Please consider to provide this tables as supplementary material and rather to present these results through box-plot in the paper.

Please remove the columns about coefficient of variation in all table reporting angles. Indeed, the coefficient of variation is not meaningful for angles. Indeed, depending on the choice of reference frame, an angle can be 1° or 91° (or even 179°). The same standard deviation (for instance 1° of SD), would result in a coefficient of variation of 100% in the first case and only 1.1% in the second. Yet, it represents the same kinematics.

L284-285: no, it just due to the choice on reference frame and the pose for 0°. See previous comment. It is the same for all degrees of freedom presented in this section.

L327: how was obtained the angular velocity? from rotation matrix time differentiation or from angle time differentiation? Please specify it in material and method

 

#Discussion

L356: ', results"

L357; not really, for that please provide time courses of joint angles

L419-420: why ? I do not think there is any impact

 

Author Response

Dear Reviewer

 

We appreciate all the constructive comments and valuable observations very much. We also thank you for the effort and time put into the review of our manuscript. We hope that we have improved the work in line with the Reviewers' suggestions. In the following response, each comment has been carefully considered point by point and replied to. Responses to the Reviewers are in a dialogue and marked with tab and italics; changes in the revised manuscript are tracked.

This study explores the comparison of kinematics between short and long serves in table tennis, offering potentially valuable insights for coaches. However, I have several concerns—not regarding the measurements themselves, but rather the presentation and analysis of the data. Moreover, despite the potential interest of this study, I believe it falls outside the scope of this journal. Other journals, such as MDPI Sports, may be more suitable for its publication.

 

Thank you very much for this comment and suggestion. However, the Special Issue, where we submitted our manuscript is untitled: Advances in Sports Training and Biomechanics, with keywords: biomechanical analysis, joint biomechanics, sport science, sports technique, kinematic etc. Therefore, we feel that our article falls within the scope of this Special Issue.

Specific comments are provided below:

# Introduction:

L68-69: ok, but what is the interest? Please assist the reader in specifying the added-value to literature.

Thank you very much for this comment. We added an explanation to this paragraph, which reads: Issues related to the description or study of the technique of performing serves in table tennis requires a lot of exploration. The serve, its different varieties and methods of execution are a very broad scope of knowledge. Searching for execution models, differences be-tween techniques, objective data regarding this execution can give many benefits to both coaches and table tennis players. However, very few works deal with the mentioned issues.

If the goal is to improve the learning of the technique for these strokes, it is necessary to provide the kinematic curves as a function of time rather than the extreme values. The extreme values are relevant for the physical preparation of athletes and should therefore be correlated with other strokes, as was done by Marsan (for instance), although this area still requires significant development.

Ref Marsan: https://journal.racketsportscience.org/index.php/ijrss/article/view/26

L83-85: In that case, please add curves of kinematics time courses.

Thank you very much for this comment and suggestion. We provided figures (multi plots) presenting changes of angles in time. In fact, they can give the best picture of movement coordination. However, it must be admitted that, due to the great diversity of task performance by the players, the graphs have become significantly "flattened".

L89: “foot tennis” ????

Thank you for this observation. It is an obvious error, probably resulting from bad translation. We corrected it

L90: please specify here what is/are the hypothesis (es)

Thank you for this suggestion. We added hypothesis, which reads now: It may be hypothesized that in many joints there are differences in the values of angles and velocities in the given events between the two types of serves. They probably result from the need to differentiate the movement parameters needed to perform two types of serves

 

# Material and methods

L118: To give readers an idea of the potential impact of fatigue between the two series, please specify an approximate total number of serves required to achieve 10 accurate serves per series.

Thank you for this important suggestion. We added this description. It stays now: Each type of serve was performed until the player had made 10 correct serves in the hitting zone (40 X 65 cm) on the other side of the table (Fig. 2). Only accurate serves were used for further analysis. The participants were asked to hit a forehand serve stroke with the maximum effort per serve type. It has been done to respect individual players' technique and style. In the vast majority of cases, players performed up to 30 serves of a given type to complete the task. The time of execution (including breaks between individual serves) was not limited.

L132-134: ok but please specify here the references

Thank you, we added the references . It stays now: “[21, 22]”. These references were and are indicated also below

L134-137: "most studies" and finally only one reference

            Thank you for this comment. We changed it to: “It was indicated in the research…”.

L150: “0.01% of cycle time” . Instead, use 'task time' as it is not a cyclic movement. Additionally, provide an approximate duration of the task to assess the significance of a 0.01% refinement in task time.

Thank you very much for this comment. We added information according Reviewer’s suggestion. It stays now: the following angles were chosen for both sides and sampled every 0.01% of task time (the approximate execution time of each serve was 1.5-2 s.):

L159-165: If calculated using the 3D identification of Euler-Cardan or Tait-Bryan angles, these angles do not correspond to the frontal plane (as they depend on the flexion/extension angle). For internal/external rotation, with a sequence of Flex/Ext followed by Abd/Add and then IntR/ExtR, the calculated angle is based on the femur’s longitudinal axis, not the pelvis.

Refer to the published paper on the joint coordinate system:
“A Joint Coordinate System for the Clinical Description of Three-Dimensional Motions: Application to the Knee” by Grood and Suntay (1983) - DOI: 10.1115/1.3138397.

Thank you very much for this comment. We have carefully checked all angles, their names, definitions and descriptions. We have carefully revised them and corrected, if needed. All of them follow ISB recommendations. We followed also Noraxon’s User Guide. From Noraxon’s User Guide:  For lower body and trunk angles the underlying Cardan rotation sequence follows the recommendations given by the International Society of Biomechanics (ISB). E.g. the rotation order of knee joint is flexion, abduction, and rotation. For shoulder joints, the algorithm is using planar angle calculations, since ISB recommends adjusting rotation matrices to the primary motion plane of a given activity.

L202-207: see above comment. And take care about the angle order in angle identification L212-219: the same.

Thank you for these observations and comments. We described it and answered above. Regarding the order of angle descriptions: we have kept the following order: upper limb, torso, lower limb

L221: reference to [24] seems inappropriate. Rather [25]?  please check all the references call throughout the text

Thank you for this observation. We checked and corrected it.

L234: maybe add a paragraph on data processing to specify which quantities/parameters will be extracted: for instance, maximal joint angle, magnitude, etc. Also include if maximal values (or mean or median) were extracted from each "cycles" then average or from an average "cycle"

Thank you for this suggestion. We added in this chapter: The following data were subjected to statistical analysis: the course of changes in joint angles during tasks; angle values in identified events; angular velocity values in events, maximum linear velocity (resultant) values in the Hitting phase.

L237: please specify the selected level of statistical significance here

We added the sentence. It stays now: “Descriptive statistics were performed and the nonparametric Mann-Whitney U test was used with a significance level of 0.05. The statistical analysis included also the calculation of effect sizes using Cohen’s d to quantify the magnitude of differences between the short and long serve (paired comparisons). Effect sizes were interpreted as small (? < 0.3), moderate (0.3 > ? > 0.5), or large (? > 0.5), providing an indication of the practical significance of observed differences. Additionally, a post hoc power analysis was conducted using paired T-tests to evaluate the statistical power of the study. The power analysis incorporated the observed effect sizes, sample size (? = 15), and an alpha level of 0.05 to calculate the probability of detecting true effects. Power values ≥ 0.80 were considered adequate, indicating a low likelihood of Type II errors, while values below this threshold were noted as limitations in the study design.

# Results

L239-242: move into “statistical analysis”, ie the previous paragraph?

            We corrected it, thank you for this suggestion.

All tables: Please consider to provide this tables as supplementary material and rather to present these results through box-plot in the paper.

Please remove the columns about coefficient of variation in all table reporting angles. Indeed, the coefficient of variation is not meaningful for angles. Indeed, depending on the choice of reference frame, an angle can be 1° or 91° (or even 179°). The same standard deviation (for instance 1° of SD), would result in a coefficient of variation of 100% in the first case and only 1.1% in the second. Yet, it represents the same kinematics. L284-285: no, it just due to the choice on reference frame and the pose for 0°. See previous comment. It is the same for all degrees of freedom presented in this section.

Thank you very much for this valuable observations and comments. We are aware that CV is a controversial measure as a parameter of variability. However, it is a relative measure, one of the few that we can use and is widely recognized as a measure of the dispersion of results. We treat this dispersion as variability. Traditionally, values of 60% are considered large. In our study, they range from several hundred to several thousand %. That is why we allowed ourselves to define them as indicating high variability in the joints. Taking into account the mentioned controversies we added in Limitation the information: The use of CV as a measure of variability is also a limitation of the work. CV values must be treated with caution because their size also depends on the values of angles. That is why we decided to leave the CV columns in the Tables as information about the dispersion of results.

 

L327: how was obtained the angular velocity? from rotation matrix time differentiation or from angle time differentiation? Please specify it in material and method

Thank you for this comment We added in the Statistical procedures chapter this information: angular velocity values (calculated as the derivative of the angle - differentiation of the angle) in events.

#Discussion

L356: ', results"

            We added “Results chapter..”

L357; not really, for that please provide time courses of joint angles

            Thank you for this observation. We provided figures with courses of movement.

L419-420: why ? I do not think there is any impact

Thank you for this question. We approached slightly different test conditions with caution, such as hall size, type of floor, lighting, etc.

 

Reviewer 2 Report

Comments and Suggestions for Authors

Dear authors, the study deals with a very interesting subject. Here are some comments and suggestions to be taken into account:

The word “analysis” could improve the title.

In citations by author, “et al.” should be used from the first mention. (Revise line 47, 69, 73, 147...)
On line 65-66 it should be: “Recent studies by Grycan et al. [14] and, Grycan and Bańkosz [15]...”

In the objective they talk about “foot tennis”, is it a mistake?

In the introduction it is more than clear the importance of the service. However, it would be clarifying to give more detail regarding the two types of service (short and long), what they consist of, what are their implications according to the exposed background.

In the methodology, it is necessary to specify the study design. In addition, in the statistical analysis it would be important to report the effect size and statistical power, taking into account that only the comparison of means test (Mann-Whitney U) is used.

In the discussion the synthesis of the results should be discussed and justified in greater depth, what the literature says about it. It is necessary to go more deeply into it.

It is suggested that in addition to the limitations, the future perspectives for this type of studies in this sport and from the perspective in which they have approached it should be projected. Furthermore, it is strongly suggested to emphasize the practical implications that should be taken into account after the findings of the study.

References 2, 3 and 4 are not referenced in the manuscript.

The format of the references is not aligned with the standards of the journal.

Author Response

Dear Reviewer

 

We appreciate all the constructive comments and valuable observations very much. We also thank you for the effort and time put into the review of our manuscript.

In the following response, each comment has been carefully considered point by point and replied to. Responses to the reviewers are in a dialogue and marked with tab and italics; changes in the revised manuscript are tracked.

 

Dear authors, the study deals with a very interesting subject. Here are some comments and suggestions to be taken into account:

The word “analysis” could improve the title.

Thank you very much for this observation. According to the Reviewer suggestion we changed the title to: Kinematic analysis of short and long services in table tennis

In citations by author, “et al.” should be used from the first mention. (Revise line 47, 69, 73, 147...)

Thank you very much for this comment. We have revised mentioned citations and corrected them.

On line 65-66 it should be: “Recent studies by Grycan et al. [14] and, Grycan and Bańkosz [15]...”

Thank you very much, we corrected it

In the objective they talk about “foot tennis”, is it a mistake?

Thank you for this comment, it is a mistake, obvious error resulting from bad translation. We corrected it

In the introduction it is more than clear the importance of the service. However, it would be clarifying to give more detail regarding the two types of service (short and long), what they consist of, what are their implications according to the exposed background.

Thank you very much for this comment. This issue seems indeed missing in previous version of this chapter. We have slightly changed the order of the issues discussed in the Introduction, also adding a paragraph that reads: “The above-mentioned classification, which takes into account long, half-long and short serves, is of great importance from a tactical point of view. The criterion for their division is the distance of the bounce of the ball (respectively: close to the net, intermediate and close to the baseline). Short serves are often used by players who attack primarily with topspin. Long serves are often used by players who prefer to switch to counter-spin play [16]. The surprise effect is also often used in the latter. Recent researches show that short serves are more often than others used in actions that end with a point being scored [15, 17]. Some researchers have also found that there are gender differences in the use of these types of serves. Pradas et al. [15] found that men tend to use short serves more often, while women tend to use long serves.”.

In the methodology, it is necessary to specify the study design.

The study design was starting from the line 109 as an Experimental set up and procedures chapter. To make it clearer now this chapter Is entitled: Experimental design and procedures

in the statistical analysis it would be important to report the effect size and statistical power, taking into account that only the comparison of means test (Mann-Whitney U) is used.

Thank you for this comment. We calculated and added suggested values. In the chapter of statistical procedures it stays now: The statistical analysis included also the calculation of effect sizes using Cohen’s d to quantify the magnitude of differences between the short and long serve (paired comparisons). Effect sizes were interpreted as small (? < 0.3), moderate (0.3 > ? > 0.5), or large (? > 0.5), providing an indication of the practical significance of observed differences. Additionally, a post hoc power analysis was conducted using paired T-tests to evaluate the statistical power of the study. The power analysis incorporated the observed effect sizes, sample size (? = 15), and an alpha level of 0.05 to calculate the probability of detecting true effects. Power values ≥ 0.80 were considered adequate, indicating a low likelihood of Type II errors, while values below this threshold were noted as limitations in the study design. A post hoc power analysis was conducted using the Excel Analysis ToolPack. The critical t-value for a two-tailed test was calculated using the function T.INV.2T(alpha; df). The statistical power was determined using the formula:

POWER=1−T.DIST.RT(t.crit−NCP;df)+T.DIST.RT(t.crit+NCP;df),

where NCP=d*SQRT(N) represents the Noncentrality Parameter (NCP). Here, d is the observed effect size, N is the total sample size, and df=N-1 denotes the degrees of freedom”.

In the discussion the synthesis of the results should be discussed and justified in greater depth, what the literature says about it. It is necessary to go more deeply into it.

Thank you very much for this suggestion. We added three paragraphs with deeper description and interpretation of our results in the Discussion chapter.

It is suggested that in addition to the limitations, the future perspectives for this type of studies in this sport and from the perspective in which they have approached it should be projected.

Thank you for this suggestion. We added, at the end of Limitations paragraph: “Future research should carefully evaluate the previously indicated importance of the speed of the racket at the moment of contact with the ball and its relationship with the type of serve. Future research should also take into account other types of serves as well as methods, very important for the effectiveness of service actions, of camouflaging, hiding the actual serve, i.e. somewhat misleading the receiving player.

Furthermore, it is strongly suggested to emphasize the practical implications that should be taken into account after the findings of the study.

Thank you very much. On the end of the Discussion chapter (before Limitations) we added our point of view for practical implications of the results of our study. It stays now: “The work performed, apart from its cognitive values (evaluation of the values of the parameters studied, indication of the use of the entire kinematic chain during the execution of serves, etc.) has great application values. The work indicates the methods of execution and differentiation of long and short serves, defining the coordination of movements, and this is information for coaches and players to use in the training process. However, our work points out also (in view of the large variability in kinematics and movement patterns observed) the need to ably the principle of individualization of sports training in table tennis.

References 2, 3 and 4 are not referenced in the manuscript.

in the line 39 there was a citation marked [1-5], which meant references to the literature list from 1 to 5. To be more precise, we changed it to [1, 2, 3, 4, 5]

The format of the references is not aligned with the standards of the journal.

Thank you for this comment. However, Applied Sciences now accepts free format submission. In the Instructions for Authors one can read: “Your references may be in any style, provided that you use the consistent formatting throughout. It is essential to include author(s) name(s), journal or book title, article or chapter title (where required), year of publication, volume and issue (where appropriate) and pagination. DOI numbers (Digital Object Identifier) are not mandatory but highly encouraged”. We checked the entire list and have found some mistakes and that somewhere volume and issue was missing We corrected it.

 

Reviewer 3 Report

Comments and Suggestions for Authors

The paper deal with the description of the results of the Kinematics of short and long serves in table tennis. Reading the paper there are several errors:

The abstract does not describes the results and the importance of the research.

.2. Materials and Methods please delete the dot in the front of 2 in the chapter 2 

the context from chapter 2.1 seems to be written with chatgpt

in the line 222 up to the end og the chapter, the numbers are in ( ), why?

Results are full of tables and is hard to understand what exactly is important.

 In Results te subchapters does not have space between text.

Graphycal results are missing.

In discussions is missing comparations with existing methods and research.

The conclussions does not well describe the research advantages and disadvantages and the results obtained.

The paper seems to be written by students and not by professionsls. It is similar to the chatGPT written. 

Author Response

Dear Reviewer

 

We appreciate all the constructive comments and valuable observations very much. We also thank you for the effort and time put into the review of our manuscript.

In the following response, each comment has been carefully considered point by point and replied to. Responses to the reviewers are in a dialogue and marked with tab and italics; changes in the revised manuscript are tracked.

 

 

The paper deal with the description of the results of the Kinematics of short and long serves in table tennis. Reading the paper there are several errors:

The abstract does not describes the results and the importance of the research.

Thank you very much for this observation. It is difficult to fit all the important findings into a limited 200-word Abstract. However, according to the Reviewer suggestion, we added a few details.

.2. Materials and Methods please delete the dot in the front of 2 in the chapter 2 

            Thank you, we corrected it

the context from chapter 2.1 seems to be written with chatgpt

Thank you for this comment. We are sorry for the impression you got. The article was written in our native Polish, the vast majority was translated by a translation agency, part of the text was also translated using dictionaries such as Google Translate or Diki. This may be the reason for the impression given by the Reviewer. We are aware of the possibilities of AI and ChatGPT. However, in our work we have not used these tools even for a single moment or in a single part.

in the line 222 up to the end og the chapter, the numbers are in ( ), why?

Thank you for this observation. We deemed these additions unnecessary and, as suggested by the Reviewer, removed them.

 

Results are full of tables and is hard to understand what exactly is important.

We present tables with angle and velocity values in a very large number of joints. The most important differences are marked in bold text. We have also added figures that will help to find what is most important. We also removed rows from the tables regarding angles and movements that were statistically insignificant, leaving only those that indicated significant differences between the serves

 In Results te subchapters does not have space between text.

Thank you, we added more space

Graphycal results are missing.

Thank you for this observation. We added figures with courses of movement in all researched joints, presented previously in Tables only regarding identified events.

In discussions is missing comparations with existing methods and research.

Thank you for this comment. According to this observation we added in the Discussion several paragraphs describing: the rules for performing striking movements, and in particular the kinematic chain, the importance of our work for table tennis training practice, implications of the presented serving motion model, referring to some added literature. We hope it helped to improve this chapter and whole paper.

 

The conclussions does not well describe the research advantages and disadvantages and the results obtained.

Thank you for this comment. We added information about described in the paper models of services and same more findings and their implications.

The paper seems to be written by students and not by professionsls. It is similar to the chatGPT written. 

Thank you for this comment. Like we wrote above we are sorry for the impression you got. The article was written in our native Polish, the vast majority was translated by a translation agency, part of the text was also translated using dictionaries such as Google Translate or Diki. This may be the reason for the impression given by the Reviewer. We are aware of the possibilities of AI and ChatGPT. However, in our work we have not used these tools even for a single moment or in a single part.

 

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors adressed all my previous concerns and I now feel the paper can be recommended for publication.

Author Response

Dear Reviewer

 

We thank you for the effort and time put into the review of our manuscript. 

Reviewer 3 Report

Comments and Suggestions for Authors

The authors improved the paper quality. In the plagism report the paper have 16% of coincidence that is in the limit of plagism. I would not recomend the paper for publication in this situation. The authors must improve the paper.

Author Response

Dear Reviewer

 

We appreciate all the constructive comments and valuable observations very much. We also thank you for the effort and time put into the review of our manuscript. 

The Reviewer comment was as follows:

The authors improved the paper quality. In the plagism report the paper have 16% of coincidence that is in the limit of plagism. I would not recomend the paper for publication in this situation. The authors must improve the paper.

Thank you very much for this comment. The high, according to the Reviewer's opinion, percentage of plagiarism can only result from the fact that findings presented in the literature sometimes were used directly, but always with references. We tried to correct this in several places in the Introduction and Discussion, so that the information provided was written in our style and our words. But probably the biggest problem was the description of the research method, which we had used in our previous studies. Therefore, we used partly the descriptions of methods included in our previous publications. In the latest version of the manuscript we have rewritten a large part of the Materials and Methods section. We hope that sufficiently. It was not possible to change the description of angles and movements, and this large part may also show signs of plagiarism, but we tried to clearly mark the citations. Unfortunately, we have no way of checking the percentage of plagiarism ourselves.

 

 

 

Round 3

Reviewer 3 Report

Comments and Suggestions for Authors

The paper seems to be published.