Stride Length Impacts on Sagittal Knee Biomechanics in Flat Ground Baseball Pitching

Round 1

Reviewer 1 Report

This study investigated the kinetic and kinematic changes related to the stride length in flat ground baseball pitching. Which might be helpful for training and injury prevention. However, there are some flaws in the rationale and methods. For more details, please see the comments below:

Major comments:

1. In the introduction, the authors have mentioned changes in temporal, physiologic, ground reaction, momentum, and performance profiles have been reported, but not the knee joint dynamics, so this paper aimed to analyze the knee joint dynamics. However, it is unclear why knee joint dynamics are so important, if this characteristic is so important, why none of the previous studies have analyzed the knee joint dynamics? Furthermore, why the dynamics in the sagittal plane was analyzed? What about the Frontal plane?
2. This study only compared two conditions (+25% and -25% stride length), such two points could not be used to represent two ranges (longer and shorter stride length). As it is not clear what is the relationship between stride length and knee joint dynamics. For example, will +10% (or +40%) stride length also lead to a larger joint moment in the BT phase? Will +40% stride length allow for greater (or smaller) knee prolusion dynamics than +25% stride length? The reviewer suggested the authors discuss this limitation in the discussion.
3. This study analyzed the lower limb dynamics, but only discussed the upper extremity injury, what about the lower extremity injury? Further, one of the major conclusions in this study is that “shortened stride length may increase strain on shoulder and elbow.” However, previous studies have already proposed this, what is the novelty of this study?

Minor concerns:

1. Line 71: what is the order of OS and US? Are the subjects always do OS at first? would the order affect the conclusion?
2. Line 72: Why the abbreviation of reduced stride is US? Why not use Under-stride here?
3. Line 82: are the kinematic and force data synchronized?
4. Line 94: How do the authors guarantee the subjects adjust the exact 25% of their DSL? is a change of 24% or 26% acceptable? The mean and SD value of step length for the trials analyzed in this study should be also presented.
5. Line 115: “2ndorder”, missed a whitespace in-between.
6. Line 132-134: Are these the results from this study? if yes, please move them to the results section.
7. Regarding the fastball velocity, whether the highest velocity during all the innings (Not just the first and last) still maintained the same?
8. Line 144: the authors did not define the abbreviation ES.
9. Figure 1: many undefined abbreviations were used in the figure legend, which does not facilitate understanding.
10. The first paragraph in discussion: the reviewer felt that this paragraph is more like an introduction but not a discussion.
11. Line 197: the results did not support the authors’ hypothesis, as they did not propose any hypothesis in the introduction, they just mentioned that “to determine whether knee joint moments and powers are sensitive to stride length changes.”

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 2 Report

In this paper, the authors provide an assessment of the physical aspects of the musculoskeletal system related to the coordinated biomechanics of the lower limbs that change in response to changes in stride in flat ground baseball pitching. After reading the manuscript, I find it interesting, but some questions arise and the quality of the manuscript need a few corrections. Please note the following:
1. Results sound good, but they should be more highlighted in the text
2. Please mention the exact approval number of the Ethics Committee on the basis of which the study was conducted!
3. The discussion section could be more extensive, especially since interesting results of the own research were obtained.
4. Please attach a section on the limitations of your research in science!
5. I propose to list the conclusions in points.
6. I understand the inclusion and exclusion criteria, but why were 19 participants recruited?
7. There is no information on the date of the survey.

Author Response

Please see the attachment

Author Response File: Author Response.pdf