The 10/5 Repeated Jumps Test: Are 10 Repetitions and Three Trials Necessary?

Round 1

Reviewer 1 Report

The authors provide a scientifically sound investigation on the number of trials/repetitions necessary for the 10/5 RJT. Overall, the paper is well written and adequately addresses the question. 

Only minor comments/edits would be recommended for this paper including:

Within the introduction, the 10/5 RJT is never fully defined. It would be helpful to provide a thorough definition of this test.

Within the introduction there is not much justification for the authors final hypothesis relating to greater RSI values occurring in later repetitions. 

Line 41 - typo - ] at the end of the sentence is in bold

Line 64 - typo - ... being reported as a reliable across numerous...

line 81 - please define the values presented - it is assumed that this is mean +- SD. 

Author Response

Reviewer 1 Comments to Author:

 

The authors provide a scientifically sound investigation on the number of trials/repetitions necessary for the 10/5 RJT. Overall, the paper is well written and adequately addresses the question.

 

Thank you for your kind feedback on the article.

 

Introduction:

 

1. Within the introduction, the 10/5 RJT is never fully defined. It would be helpful to provide a thorough definition of this test.

 

Thank you for your constructive comment. We have updated lines 31-34 with the following: “This test requires the subject to execute 10 maximal vertical rebound jumps, whilst attempting to maintain a ground contact time (GCT) of <250 ms. Of the 10 repetitions recorded, the top five that display the greatest jump height, whilst minimizing GCT below 250 ms, are used for subsequent analysis [1].”

 

2. Within the introduction there is not much justification for the authors final hypothesis relating to greater RSI values occurring in later repetitions.

 

Thank you for your comment. We have added some further justification in relation to the final hypothesis in lines 81-83 with: “Due to the requirements of the 10/5 RJT, subjects may adopt a pacing strategy because they know 10 jumps are to be completed per trial. Therefore,”

 

3. Line 41 – typo – ] at the end of the sentence in bold.

 

Thanks for your comment. We have made amendments to this sentence and ‘]’ is no longer highlighted bold.

 

4. Line 64 – typo - … being reported as a reliable across numerous…

 

Thank you for your noticing this error. We have now removed ‘a’ from this sentence.

 

5. Line 81 – please define the values presented – it is assumed that this mean +- SD.

 

Thanks again for your constructive feedback. We have now updated line 89 with the following: “– values reported as mean ± standard deviation)”

 

 

Reviewer 2 Report

Congratulations on a manuscript that has value to both the research literature and practical application of the RSI. 

Comments for author File: Comments.pdf

Author Response

Reviewer 2 Comments to Author:

 

The authors’ have provided a valuable investigation into the 10/5 repeated jumps test. The investigation fills a current gap in the literature in that it is the first (to my knowledge) to provide an analysis into the effect of jumping repetition on RSI scores. The findings of the investigation improve upon current literature but also have practical meaning. Results support athlete monitoring using 1 trial of 10 jumps, which gives practitioners confidence in using the 10/5 repeated jumps test for efficient athlete monitoring. The manuscript was written with high quality, focussed on relevant literature, and provided an accurate and in-depth coverage of study rationale and interpretation of results. I do have feedback for the authors that I feel would strengthen the manuscript. Given the writing quality of the manuscript, I feel that this publication is ready following author address of feedback. Thus, I recommend acceptance of this manuscript after minor revision.

 

Thank you for your kind words and feedback on the paper.

 

Introduction:

 

The introduction was complete and effective in setting up the rationale for the study. The 9% variability in 10/5 RJT reported by Harper et al. is very similar with my anecdotal experience using the RSI (depth jumping) in athlete monitoring.

 

Thank you for your comments.

 

Methods:

 

My main feedback for the authors regards their approach for computing jump height. The authors report using a force platform to measure GRF during the 10/5 RJT. Why not integrate the GRF data to attain jump height? There are known threats to internal validity with using flight time to estimate jump height and deriving jump height directly from GRF data is typically viewed as preferable.^1,2 The authors could consider repeating their statistical analysis using jump heights derived from GRF data or, at minimum, report the threats to internal validity associated with the flight time method.

 

1. Baca A. A comparison of methods for analyzing drop jump performance. Med Sci Sports Exerc. 1999 Mar;31(3):437-42. doi: 10.1097/00005768-199903000-00013. PMID: 10188749.
2. Louder, T., Thompson, B. J., Banks, N., & Bressel, E. (2019). A mixed-methods approach to evaluating the internal validity of the reactive strength index. Sports, 7(7), 157.

 

Thanks for your comment. You raise a good and valid point in regard to the calculation of jump height. The 10/5 repeated jumps test is a fairly new and emerging test that is being assessed via a force plate both in a practical setting and in academic research. Flight time estimated from jump height, like you have mentioned, is prone to error irrespective of the jump test performed. However, there are gaps in the research that need addressing about how to best integrate force-time for this test. Within the manuscript, we have acknowledged the threat to internal validity with using the flight time method to estimate jump height. Please refer to lines 336-346: “Furthermore, in the present study, jump height was estimated from flight time using a specific formula, mentioned above [19]. Previous research by Louder et al. [32] highlighted threats to the internal validity associated with using the flight time method of estimating jump height, as opposed to using take-off velocity, when applied to the DJ. Whereas the DJ involves a single rebound jump repetition per trial, the multi-repetition nature of the 10/5 RJT makes it difficult to accurately numerically integrate the net force-time record to yield velocity. This is due to a concept know as ‘drift’, which can be a problem when performing force plate assessments of exercises that involve larger sampling durations and multiple impacts. As very few studies to date have conducted the 10/5 RJT using a force plate, further research is required to ascertain the most appropriate methods of processing the resultant force-time record to allow for additional variables to be generated from this test (and their efficacy explored).”

 

Results and Discussion:

 

I have no major points of contention with the results and discussion. I thought the authors were clear in the presentation of results and were highly accurate and thorough in discussing the meaningfulness / interpretation of results. I would like to refer the authors to a 2015 manuscript by Beattie and Flanagan.³ In figure 3, the authors present upper and lower SEM. SEM can be used to represent minimum detectable difference (meaningful change). A suggestion for the authors would be to briefly discuss the applicability of using the SEM range as a ‘bandwidth’ of performance that is influenced by bio-variance. Although it is just my opinion, I feel that establishing a normal range of RSI performance has practical value, since trial-to-trial RSI variability is reported as high as 10%. For example, the SEM range could be used to reflect normal variability in performance. If an athletes’ follow-up test performance falls above or below the SEM range, then practitioners may feel confident that performance may have changed, for better or worse.

 

3. Beattie, K., & Flanagan, E. P. (2015). Establishing the reliability & meaningful change of the drop- jump reactive strength index. J Aust Strength Cond, 23(5), 12-18.

 

Thank for your kind comments and constructive feedback. Line 322-331 now reads: “Furthermore, it has been suggested in previous work that the upper- and lower-bound SEM can be used to represent the minimal detectible difference or change in RSI derived from the DJ test [4]. In line with this suggestion, it may be that practitioners could calculate the SEM for their athletes’ 10/5 RJT RSI scores, as shown in Figure 3, to create a ‘bandwidth’ of performance that is influenced by bio-variance. This would help practitioners to establish their athletes’ ‘normal’ range (i.e. variability) of RSI scores for the 10/5 RJT. Subsequently, if a change in an athlete’s performance is above or below the SEM range (similar to what is shown in Figure 3), then this could indicate that a change in performance has occurred that is either positive (above the upper SEM) or negative (below the lower SEM).