Changes in Countermovement Jump Height in Elite Volleyball Players in Two Competitive Seasons: Consideration on the Technique of Execution of the Jump

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Thank you for your opportunity to review the manuscript ‘Effects of execution of the countermovement jump on jump height in professional volleyball players: comparison of two competitive seasons’. This study aimed to evaluate changes in jump performance in professional volleyball players during their two competitive seasons after introducing different executions of the jump test.

My concerns are as follows:

Generally, the study carried out by the Authors is not an experiment in design for the following reasons:

1. There was no manipulation of the independent variable;

2. There was no randomization of study participants.

Therefore, the Authors cannot conclude that there is a causal relationship between dependent and independent variables. In the present case, only the ‘association’ / ‘correlation’ between dependent and independent variables can be explored. Throughout the entire manuscript, it is necessary to change the cause language in that manner it does not contain sentences and terms that indicate a causal relationship (namely, ‘experiment’, ‘effect’, ‘influence’, etc.). In the alternative, I propose that the title should be adjusted to the ‘pilot study’.

On the other hand, the design of this study is more similar to the observation cohort study, where the same particular group of study participants was observed for a certain period of time without manipulation of the independent variable.

Nevertheless, the sample size (in terms of nine study participants) is very small (i.e. insufficient) for the purpose of study results generalization.

It remains unclear why 'Subjective wellness questionnaire' was used. This measurement has no connection with the aim of this pilot study.

It remains unclear why ‘Subjective wellness questionnaire‘ was used. This measurement has no connection with the purpose of this study.

All in all, I suggest that the scientific basis for extrapolating the results obtained by this pilot observational study to the athletes' groups competing in other sports is absolutely restricted.

Author Response

Our response can be found in the docx/pdf file, thank You for taking Your precious time to improve the quality of our manuscript. 

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Please refine your study, ensuring comprehensive analysis and interpretation of the data, and enhancing the overall credibility and applicability of your research findings:

1.      Explain how the fatigue level of players before each test affects the jump height results. Fatigue can reduce muscle power and performance. If the study did not control or measure fatigue levels before each jump test, the results might not accurately show the effect of the jump technique alone.

2.      Explain how the statistical power of the study was sufficient to detect a meaningful difference in jump heights between the two seasons. Statistical power depends on the sample size and effect size. A small sample size can result in low power, which means the study might not detect small but important differences. Increasing the number of participants or calculating the power would help verify the findings.

3.      Explain how specific physical training sessions correlate with changes in jump performance over the seasons. Training intensity and type can directly affect jump performance. Without linking the training data to jump results, it's hard to say if the jump technique or the training program had more influence on the changes observed.

4.      Jump techniques can vary in how they stress athletes' joints. Was there any monitoring of joint stress or potential injury development due to different jump techniques? Without data on joint health or injury occurrence, the long-term effects of these techniques remain unclear. Including this could provide a more comprehensive view of the techniques' safety.

5.      Recovery strategies like stretching, ice baths, or massage can affect muscle performance and fatigue recovery.  What were the recovery protocols followed between testing sessions, and how might they have influenced the outcomes? Without knowing these, we can't fully understand the factors influencing the jump height results.

6.      The mental state of athletes, such as anxiety or motivation, can influence performance. Was this considered in the study? Athletes' mental state can significantly impact performance, especially in repeated tests like the CMJ. If not assessed, the results might reflect psychological variations rather than just physical capabilities.

8.      Cite what are the implications of repetitive jump testing on athletes' musculoskeletal health, particularly the spine and lower limbs. Repetitive jumping can lead to stress injuries. The study should address whether any preventative measures were taken to avoid such injuries and discuss the potential long-term consequences for the athletes.

9.      Nutritional status can affect performance. Was there any control or monitoring of the athletes' diets? Nutrition affects energy levels and muscle recovery. Without monitoring or controlling diet, variations in nutritional status could skew the results of the performance tests.

10.   Individual differences and external conditions like sleep, stress, and overall health can influence performance. Explain how the study accounted for individual variations in physical condition and external stressors that could affect the results. Not accounting for these could compromise the study’s validity. Including these factors could strengthen the study's conclusions.

11.   You must point out these limitations of your study in the discussion of the article:

a)      The study only included nine volleyball players. A small number of participants can make it hard to generalize the results to all professional volleyball players.

b)      There is no control group that did not change their jump technique. Without a control group, it's difficult to be sure that the observed changes were due to the technique change and not other factors.

c)      The study relies on the same athletes being observed over two seasons. Changes in their physical condition, training intensity, or external factors could influence the results.

d)      The study did not use the same exact method to measure jump height every time. Different conditions or equipment could affect the accuracy of the results.

e)      Athletes' motivation or fatigue on the day of testing could affect their performance, influencing the results independently of the jump technique.

f)       These limitations suggest that while the study provides valuable insights, the findings should be interpreted with caution and possibly verified through further research with a larger sample size and a controlled design.

Author Response

Our response can be found in the docx/pdf file, thank You for taking Your precious time to improve the quality of our manuscript. 

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Accept.

The revised manuscript meets the required standard.   Best Regards

 

Reviewer 2 Report

Comments and Suggestions for Authors

I have thoroughly reviewed the revised version of your manuscript and would like to express my appreciation for the diligence and care you and your co-authors have taken in addressing the comments and making necessary corrections.

 

Your responses to the previous feedback were clear and comprehensive, and the revisions made have significantly strengthened the overall quality of the manuscript. I am pleased to note that you have effectively addressed the concerns raised during the review process.