Kinematic Determinants of the Swimming Push Start in Competitive Swimmers

Round 1

Reviewer 1 Report

The paper's main purpose was to analyze the kinematics of push start. It’s an interesting topic, since, as the authors state, most of the starts in the swimming training routine are push starts, however the lack of criteria in the regression models severely compromises the results and a more rigorous approach must be adopted.

The selected kinematics variables were called “determinants”, but there was no analyses or explanation to support that claim. All the variables were put in one pre-determined regression model without any mechanical or theoretical background and there was no control of overfitting by the introduction of unnecessary variables. The variables are also correlated between themselves, since the final velocity of one sub-phase is the initial velocity of the next one, and it was also not considered. The discussion and conclusion should be rewritten after proper data analysis.

 

Specific comments

 

57-63 – Confused. Please rephrase.

74- What do you mean by “performance classification”?

96- What was the camera resolution?

105- How the hip center was identified? There was any marker in the swimmer to assist in digitizing?

121- Overall is not a good term for the distance and velocity until the end of the underwater phase, since you also call the 10m time as overall performance and you also used the word “overall” in other contexts too, as far as I understand.124- By your results I believe that you also performed ANOVA. Please report it.

125-127 – Did you test the normality of the residuals? The same for lines 129-131.

128- Please, also include the thresholds to evaluate the eta squared.

134- The names of the variables are not in English in the equation.

143- What is the subscript in your “F”? I believe that it should be the two degrees of freedom.

143-  Make clear across the manuscript which comparison you are reporting, main effects, or interaction.

Table 1- What the letter ‘c’ indicates?

Figure 1- Include the trendlines and equations. Also, report r² instead of r, to keep consistency with table 2.

Table 2- Include the legend for the “*”.

198- Evidence of what?

199- Why meaningful?

201-204- Confused. Please rephrase.

207-209- Based on what? Why those specific time intervals are relevant?

212- You can’t establish a cause-effect relationship.

242-245- The sub-phase transition depends on the decision of the swimmer to initiate the leg kick action. Mechanical constraints could influence this decision, as you state, but the swimmer's expertise and personal preference are the determinant factors.

286-289- Why not report those variables from your own data?

295- greater impulse

326- Most?

325-330- It doesn’t make sense…

 

350-361- You only repeat your conclusion.

Author Response

Please see the attachment

Author Response File: Author Response.docx

Reviewer 2 Report

1. In the description of the research methods, only the absolute error for the coordinates is given. And what is the relative error (in percent) for the designated sections and for the average speed? Taking into account errors of the method such as camera frequency, accuracy of determining points in a computer image, parallax errors of the movement of water, etc.

2. I am not sure if the graphs in figure 1 contribute anything. It is enough to point out significant correlations. But maybe it is at the editor's disposal.

3. I suspect that the transition to the second phase is dependent on reaching a certain speed. The sliding phase is the fastest, and when the athlete slows down, he adds a kick to maintain speed. But he has to do it below the maximum speed he can get with the kick or it will inhibit the movement. So it would be worthwhile to examine the maximum speed with a kick here and compare it to the speed of the transition to the second phase.

 

Author Response

Please see the attachment.

Author Response File: Author Response.docx