Concurrent Validity and Reliability of My Jump 2 App for Measuring Vertical Jump Height in Recreationally Active Adults
Round 1
Reviewer 1 Report
Generally, a well written manuscript looking at equipment validity and reliability. Although the validity and reliability of vertical jump height recorded with different systems has been confirmed, the measurement accuracy of each system must be evaluated and cannot be easily compared. That is why there is a constant need for works on this subject.
However, I have few comments:
- The title is inaccurate: "measuring vertical jump" - you don't measure the vertical jump directly, just the vertical jump height; it's a too big mental shortcut, you need to be more specific in both the title and the entire manuscript. Please, consistently improve.
- Line 28: "to measure physical performance"... as above. You should write "to measure vertical jump (height) performance".
- Line 28: are you sure you wanted to use the word "robust"?
- Line 47: "All of the mentioned instruments…" - I think it would be safer to write "most of them".
- Lines 68-69: 36 participants =/= 18 women + 26 men, so how many people?
- Your division of CMJ jumps is rare (CMJ + CMJ free arms) - it would be clearer for the reader to use the names: ACMJ (akimbo CMJ) and CMJ with arm swing.
- An interesting addition to the article would be to mention other calculation methods for determining the height of the vertical jump, e.g. in the limitations section. For example, Struzik and Zawadzki (2019) mention a method based on a force-displacement curve. Please complete with appropriate citations.
Author Response
Please see the attachment.
Author Response File: 
Author Response.docx
Reviewer 2 Report
General comments
The aim of the paper was to compare the My Jump 2 app, which measures jump height with the smartphone’s video camera, with Optojump system. There are previous papers comparing My Jump with other devices, but this paper covers a wider range of jump tests and is applied to a different sample. The paper is well justified, planned and written, and adds to the sports sciences’ knowledge. However, I have some concerns that need to be addressed.
For example, separate analysis of each sex is not justified. The main purpose of the study is to compare two measurement methods, so I see no need to analyse separately males and females. The results are very similar in both sexes, so some tables and figures are almost redundant. Probably if you pool all the participants, the sample is bigger so more statistical power is achieved, and the range of measurement in each variable is wider, which is positive to compare the instruments.
Specific comments
Line 34: the first paragraph seems to be disconnected from the rest of the paper. It gives the false impression that the article will focus in health and aging. It could be removed or rewritten.
Lines 47,49: I would not include video among the “not cheap and not widely accessible methods”. On the other hand, many smartphones with high speed cameras, as the iPhone, can be quite expensive.
Lines 70, 73, 107: keep the use of the past tense: “…who were recreationally…”, “…regularly participate in vigorous…”, “Participants were instructed…”.
Line 81: something is missing in “…they carried out a standard warm-up consisted of jogging…”
Lines 96, 97, 101: hands on their waist, better than hips.
Line 112: I find the 95% CI nomenclature confusing, the hyphen can be confused with the negative sign. It would be better to keep the format you use later (0.97; 0.99).
Line 120: It is very important to describe the height of the camera and the plane recorded, as it determines the sensitivity to establish the contact photogram or if one foot touches the ground first. According to figure 1, appears to be correct, but should be described in the text.
Lines 206-209: actually, the value of R2=0.74 in females SJ appears to be mainly due to two extreme cases. It would be smoothed out if all the data (men and women) were put together.
Line 233: 2.3 cm, leave a space in between the number and the symbol.
Lines 248-249: Comparing My Jump with Optojump is more appropriate because they are based on the same paradigm, measuring the flight time, with its advantages and disadvantages.
Lines 257-261: this is another reason to join male and female data.
Lines 262-263: The SJ jumps with downward movement prior to the upward movement should have been discarded, as stated in the methods section.
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Reviewer 3 Report
The study aims to investigate the construct validity of the my jump 2 app against the opto jump equipment and the test re-test reliability of the My Jump 2 app using an I-Phone X video camera(240 frames per second). The research question is interesting for applied sports scientists and practitioners. However, the manuscript has several limitations that need to be addressed.
The study design is acceptable if my question about familiarisation can be answered.
The statistical analysis is in parts decent but lacks clarity and it would be useful for readers is within and between session intra-individual variance was reported. A suggestion would be to apply the root mean square error approach. This would add interesting results that readers could make use of. This paper may help you Maiwald, C., Axmann, D., & Grau, S. (2011). Measurement error in footwear research biomechanics. Footwear Science, 3(2), 117-124.
I have written some comments that may help improve this paper.
Title suggestion: Concurrent validity and reliability, of My Jump 2 app for measuring vertical jump in recreationally active adults.
I don't think that you investigate the usefulness of the App to a great deal!
Introduction
In general, the introduction lacks clarity and does not discuss the current state of the art research and gaps in the current research. Gaps not discussed are the relevance of including a female group, eg lower jump height and possible impact on the calculation of jump height and how this impacts CV% and error. Neither do the authors discuss the validity or importance of measuring SJ, CMJ, and CMJ free arms, for example, previous research in test re-test reliability of the different types of jumps and the relationship between these jumps and sports performance. Neither do they discuss the expected impact of 120 fps vs higher sampling rate, such as 240 in the iPhone-X!
2. Materials and methods
2.1 line 68 you write 36 participants, but 18+26 = 44
line 70. are they recreationally active, or recreationally active in a local gym. I think the former! Perhaps you could rewrite this to clarify how sample selection occurred.
line 76. when did familiarization take place? Was it the same day as the first test occasion? If so this should, at least, be discussed in your limiations
line 80 see comment about line 76
Line 81, was it a standardized warm-up? Why was this warm-up chosen? How long did participants warm-up for, what calisthenic exercises were chosen.
line 83 (may be wrong here) I think you need to write IL out in full and add country.
line 84 -85 is not clearly written. "The leg length and height at 90° were 84 measured using a measuring tape to the nearest 1 cm" this need to be planted, perhaps the previous study using the My Jump app could be a guide?
line 84-85, which order were the jumps performed, and why? What rest was given between jumps was it 3 jumps then 2 minutes rest or 9 jumps with 2 minutes rest between each jump? Why was this rest period selected?
Line 89 "The highest jump of each technique was taken into analysis." why the best and not all three or the average of the 3? using all three jumps would allow for the within-subject and within-session variance to be investigated.
Line 97, were many jumps excluded?
Line 112: Is the concurrent validity for the jump height of flight time?
Line 110-113:the optojump set-up is not described. How was it set up?
Line 120, What height was the camera stationed at, was it held (manually) or placed on a stand/tripod. Where in relation to the athlete was the camera placed, in front, behind, diagonally in front.
Statistics:
The use of Hopkins SWC confuses me, why have you chosen to use this method?
Results
Line 146: Consistency,! your write out Eighteen in text and 26 numerically? Why is this? The sentence is, in any case, redundant as the data was presented in the previous section.
Table 1. The methods section did not (in my opinion) clearly state you collected data on training age and training volume/time. The title for table 1 should be not be aligned to the center (but to the left).
Was the optimum system used in both test and re-test? What was the reliability of this?
Table 2:What is "rating"?
Fig 2-4, Som of these findings are well reported, why have you not discussed the mean bias (which is positive) for almost all comparisons.
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Reviewer 4 Report
The present study show the validation of an smartphone app on adult recreational people. This app already has several validation study on similar population. Despite this, the work matters to physical therapist and sports professionals, helping them with an affordable reliable alternative to other devices. English is correct and style is very good.
-The introduction make sense with the topic and is crearle defined.
-The design is adequate for the objective proposed.
-Methods are well described.
-Data analysis is well designed and performed.
-Tables are clear and opportune
-Figures with landing/take off pictures are useful and visual. Plots also provided good information.
-Conclusions are consistent with the findings.
-References are adequate and updated.
As suggestion, a more precise description of the sample would be desirable. Affirmations like "All participants were asked if they regularly participate in vigorous physical activity an about the type of activity" and "participants who are recreationally active in the local gym" are poor at describing the quantity of exercise or hoy active the participants were.
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
The manuscript was revised my corrections request in the first round.
