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Your manuscript is now suitable for acceptance. Thank you for your diligent efforts in addressing the reviewer comments.
[# PeerJ Staff Note - this decision was reviewed and approved by Mike Climstein, a PeerJ Section Editor covering this Section #]
**PeerJ Staff Note:** Although the Academic and Section Editors are happy to accept your article as being scientifically sound, a final check of the manuscript shows that it would benefit from further editing. Therefore, please identify necessary edits and address these while in proof stage.
The revision has strong written English, graphic, and table presentation of results. Data and coding are uploaded to Harvard Dataverse.
Adequate data collection procedures and weaknesses in data smoothing of the racket coordinate data at impact are not acknowledged in the limitations. Good improvement on revised statistical analysis (multiple ANOVAs on likely correlated dependent kinematic variables).
Improved statistical analysis and presentation of data. Wording has also improved in not considering associations as causative.
The authors have done good job addressing the critiques of the reviewers and are commended for collecting a large dataset, submitting raw data and code for a moderate sized sample of skilled male tennis players. Consider the specific suggestions on improving the clarity of the narrative limiting your application recommendations based on study design and convenience sample.
Line Number
50 Improve clarity: . . . . or segments over key stroke phases, without documenting inter-segmental coordination between joints and their effect of racket speed prior to ball impact.
73 Improve clarity: . . . and trunk in forward throwing/striking actions is typically small . . .
377 . . . may align with . . .
389 . . . overall performance that can be validated.
409 Add sentence that these training hypotheses should be confirmed with training studies.
439 movements may be essential . . .
442 Also consider noting the need to confirm the hypothesized benefit of training of flexibility and coordination in both non-dominant and dominant pelvis-trunk movements for similar and other populations of tennis players.
The reviewers have highlighted areas for improvement in clarity or reporting of your research. Please address the specific comments of the reviewers.
**PeerJ Staff Note:** Please ensure that all review and editorial comments are addressed in a response letter and that any edits or clarifications mentioned in the letter are also inserted into the revised manuscript where appropriate.
**Language Note:** The review process has identified that the English language must be improved. PeerJ can provide language editing services - please contact us at [email protected] for pricing (be sure to provide your manuscript number and title). Alternatively, you should make your own arrangements to improve the language quality and provide details in your response letter. – PeerJ Staff
Strong written English and adequate review of recent research on the topic. There are still some minor issues in clarity of reporting statistical tests, results and limitations. Data and coding are uploaded to Harvard Dataverse.
Adequate data collection procedures but with weaknesses in data smoothing of the racket coordinate data and statistical analysis (multiple RMANOVAs on likely correlated dependent kinematic variables). These are now, however, acknowledged in the limitations.
The wording of results and interpretation has been improved and is now acceptable.
The authors have done a good job addressing the concerns this reviewer had with the initial submission. See the specific comments for clarifications to assist readers.
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42 . . . how preparatory running speed influences stroke mechanics . . .
44 preparatory transverse plane trunk rotation . . .
76 demonstrated positive associations . . .
94 . . . how different preparatory court movement distances . . .
212 Clarify wording on the number of RMANOVs run. Four or eight? Repeated measures on the distances, not dominant and non-dominant side correct?
398 . . . racket speed prior to impact was underestimated due to distortion by smoothing through impact (Provide citation of first documentation of this effect: Knudson & Bahamonde 2001 J Sports Sci or one of several subsequent confirmations in several sports-- Tanabe & Ito 2007 J Sport Health Sci; Reid et al. 2012 J Appl Biomech; Gozalez & Knudson 2019 37th ISBS Proc Archive
399 Add a sentence about the limitation of inflation of the experiment-wise type I error rate with the use of four RMANOVAs on likely correlated dependent variables from the same dataset. Something like: The study also limited by the use of four (or 8? Were dominant and non-dominant) RMANOVs on dependent variables, without correction for inflation of the experiment-wise type I error rate.
Good improvements on Table 1
Several of the figures are still hard to read, so please be sure high-resolution images are used and/or legend fonts are larger. Sometimes graphs can be enlarged by small changes in scale and using the figure caption text rather than legends to identify curves.
English should be improved (I suggest to talk with an expert). The structure of some sentences also needs to be reviewed.
Some further references and justifications could be included in the discussion.
I think that some explanatory figure could be included in procedures (for example for the CRP variable, which is the most important).
I see the second objective as different from the first. I would include it as a measure of data validity.
Some findings need to be better explained, and a biomechanical explanation based not only on muscle activity or muscle elastic capacity is needed.
Include further explanations of some of the theories included in the discussion.
I think the design is correct. The only thing I don't understand is comparing subjects with a higher stroke speed to those with a lower stroke speed. It could be better justified.
The conclusions seem appropriate
I attach a pdf file with some suggestions
Your work can contribute substantially to the field. However, the reviewers have identified areas for improvement in the justification and explanation of statistical tests, reporting of results (remove implications of causation from associative assessments), and reducing the length of the discussion.
**PeerJ Staff Note:** Please ensure that all review, editorial, and staff comments are addressed in a response letter and that any edits or clarifications mentioned in the letter are also inserted into the revised manuscript where appropriate.
Strong written English, adequate review of recent research on the topic, but the reports need improvement in clarity of written communication: Both specifics from previous results and specific results of the current study. Figures need improvement to be readable (see specific comments to the author). Data and coding are uploaded to Harvard Dataverse.
Adequate data collection procedures, but with weaknesses in data smoothing of the racket coordinate data and statistical analysis (multiple ANOVAs on likely correlated dependent kinematic variables). Why are not all the dependent variables correlated with each other to see which variable may account for most of the variance in racket speed?
Needs improvement in controlling alpha inflation, graphs, and limiting inferences to the design and statistical analysis of your data. Associations should not be interpreted as causative, nor should comparative results be inferred to be readily applied to other tennis players.
The authors are commended for collecting a large dataset, submitting raw data and code for a moderate sized sample of skilled male tennis players. The report strives to connect previous biomechanics and motor control studies about coordination and the two goals of performance enhancement and injury risk reduction. See the specific comments for details on improving the clarity of written communication, data smoothing and statistical analysis, reporting your data, and limiting your inferences to the study design and statistical analysis of data.
Line Number
1 . . . Differ Across Preparatory Court Movement Distances . . .
10. Revise to report the number of RMANOVAs and correlations performed on your numerous dependent variables
11 Note what plane(s) of motion were analyzed for pelvis-trunk coordination and the number of court movement distances studied
26 Consider deleting vague and exaggerated inference implied by the use of “critical.” You present no data that certain pelvic-trunk rotation patterns do not result in adequate racket speed or injury during data collection. If a variety of coordination patterns are effective, they matter, but you do not have evidence that they are critical for anything
27-29 Revise this vague recommendation and reference to “optimizing” performance. You have data only on 18 male, college tennis players. Perhaps specifically recommend future research to confirm some specific coordinative coupling in skilled male tennis forehands
34 . . . the court distance
35 Revise unclear wording here. Are these coaches and players referring to court movement to intercept shots or stroke movements?
38 Revise to be clearer. What is meant by entry speed? Speed of what?
39 Expand the summary of key results of this study.
45 Good point, but cite a different source with direct evidence of the association between racket speed and resulting ball speed. Does reference 6 present data on this association, or is it an opinion expressed by these authors?
49 -51 Great points. Add a sentence that the sequence or timing of movements also means that contributions to movement outcomes are a factor in biomechanical contributions
57 . . . often exhibit “block” (unison pelvic and trunk axial rotation).
66. . . In maximal effort upper extremity movements, the role of sequential/differentiated pelvic and trunk axial rotation (a.k.a. the X-factor in golf) remains unclear across many sports.
70 Report size and size of the associations when they are observed
73 Clarify the plane of angular velocity being referred to here, transverse?
147 Report when coordinate data were collected relative to the main temporal events of a tennis stroke. Something like: Markers were tracked from dominant foot contact with the ground until impact?
162 Add details on how you calculated racket speed relative to your marker data. Given that the speed of the racket is influenced by the distortion of the data by smoothing through impact (Knudson & Bahomonde, 2001, J Sports Sci). If the data is terminated at impact, then the same depression/distortion will occur if there are no padding points added to the data. Either reanalyze the data correctly or note the likely distortion of the racket speed at impact in the limitations paragraph of your report
163 “forward rotation” is unclear. What plane of motion (global transverse plane) from what model of the racket using what markers?
167 Revise this unclear operational definition of the “norm linear?” racket speed. Was this the 3D resultant velocity one frame before impact or the first frame of visually identifiable contact of the ball and the strings? Either definition likely creates a depressed distortion of the actual speed of the racket at the moment of impact. The Knudson & Bahomonde results have been replicated in other studies of tennis strokes with sampling rates over 1000 Hz
184-191 and 197-199. Good description of your methods. Clarify what time intervals within the phases of the forehand stroke these are calculated for your SPM.
194 . . . racket speeds at impact?
212-216 Again, please be clear on the number of ANOVAs you run. A Bonferroni correction with a single ANOVA with SPM is appropriate. Doing multiple ANOVAs also inflates your experiment-wise type I error rate. How are you defining statistical significance and controlling this in your whole experiment, given the multiple ANOVAs? Bonferroni overcorrects (inflation type II ) errors, so the easiest technique is a progressive alpha correction (e.g., Holm 1979 Scand J Stat or others)
Figure 1: Please provide a higher resolution image of the figures. I blew up the figure to 400% and could still not read the legend to follow the results. The editors also need to weigh in on this issue because the numerous curves and SDs shading make it difficult to see the specific variables plotted, patterns, and differences the author(s) are wanting to communicate. Perhaps separate into more graphs like Figure 2.
Figure 2 is better than Figure 1. Perhaps both figures can move the legend into the Figure caption to allow a better look at the data. For figure 2, you should refer to the high and low racket speed groups to remind readers you split the players in half-May top half and bottom half racket speed?
252 This is not a thesis/dissertation, so there is no need to repeat the purpose statement in the discussion
254-258 Clarify with clear wording of your key results and the organization of the discussion section (e.g., several significant differences in transverse plane CRP of pelvis-trunk rotation in forehands of male skilled players across . . . )
262 and 264. It is good that you are now explaining the differences indicated by the SPM. However, a pelvis segment does not “internally” or “externally” rotate. These are anatomical terms for the hip joint rotation in the transverse plane. I don’t think you measured either, just the transverse plane rotation of the pelvis and trunk segments in the global horizontal plane, correct?
267 Same problem as above. What is trunk rotation and compared to what prior to ball impact? Less transverse plane trunk rotation toward the stroke direction with what CoM speed compared to what CoM speed prior to the stroke?
269-285 This section is unclear. Your method claims the players used open stance strokes, in which both lower extremities have “planted” feet to push off with. Why would they be using any crossover steps that would indicate a “square” or “closed” stance? This overall coordination element of your discussion needs to be its own paragraph, probably later in the discussion once you have described all the coordination differences in your study. Differences in trunk and upper extremity transvers plane coordination have also been observed between stroke stances (Knudson & Bahmonde, 1999, Biol Sport 16:3-10) and in muscle activation between gender (Knudson & Blackwell, 2000, Int J Sports Med 21:321-324)
286-313 Another huge paragraph mixing different terminologies (kinematics/rotation, tension arc?, co-activation, strength, control) and vague rotation about an unknown “planted” foot. Please clarify and add what hip anatomical joint angles in both legs contribute to the transverse plane motion of the pelvis?
332 Rephrase this as a hypothesis for future prospective injury research for confirmation, and then potential application in the future
342 Report the moderate to large negative correlations... and refer to the figure illustrating your observation. Remember correlations are descriptive statistics and cannot infer causation. They only tell you about the strength of the covariation
347 . . . shortening when immediately preceded by counter rotation, revered by an eccentric muscle action.
353 Rephrase this as a hypothesis for future prospective training research for confirmation, and then potential application in the future
357 moderately, negatively correlated
376-391 Add limitations of a moderate sample of advanced male players from one university and smoothing effects of racket speed noted above. Also note that besides individual differences, each player and the multisegment nature of tennis strokes likely have stroke-to-stroke variability in coordination that interacts with the normally high variation (open) environment of tennis groundstrokes; hence, groundstroke coordination is not monolithic
418 Rephase to refer to your skilled male players
422 Again, consider describing the strength of the associations and removing “critical” as an adjective.
426 Again, rephrase to say forehand of your skilled players confirmed previous reports of increased coordination variability
430 Delete “key” and be more clear as to what transverse plane angular motions tended to be associated with faster racket speeds at impact in male skilled tennis forehands
433 Delete this key point or modify it to recommend future prospective research to confirm what hypothesis(es)?
The manuscript entitled “Pelvis-Trunk coordination differs across movement distance during tennis forehand" compares pelvis-trunk coordination in forehand strokes executed with different movement distances. It also studies the relationship between kinematic variables of trunk rotation and ball velocity. It seems to be a good work that uses a complex biomechanical marker model and advanced statistics. However, before being published, there are a number of issues that need to be improved/clarified.
See in the PDF the reply.
Original, but some questions need to be clarified and better justified.
See in the PDF the reply.
The conclusions are too long. Summarise. More details in the PDF.
See the attached PDF
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