-->PONE-D-25-59844-->-->The effect of a body size index on physical fitness index is more pronounced in boys than in girls: evidence from a cross-sectional survey based on Tibetan adolescents aged 13-18 years in high-altitude areas of China-->-->PLOS One

Dear Dr. Liu,

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PLOS One

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Additional Editor Comments:

1.The manuscript provides different sample sizes in different sections. The abstract and methods state 3819 valid participants, whereas the introduction states 3817 adolescents were tested. In the Results section, the text reports 3817 valid questionnaires, including 1908 boys and 1909 girls, while Table 1 reports 1909 boys, 1910 girls, and 3819 total.

2. Table 1 contains multiple apparent statistical errors. For example, the text states that ABSI did not differ significantly by sex, with t = 1.594, P > 0.05, but Table 1 reports P < 0.001 for ABSI. Other examples also require verification. Waist circumference is reported as 69.28 ± 7.44 cm in boys and 69.28 ± 7.08 cm in girls, with t = 0.030, but the P-value is reported as 0.002, which is inconsistent. Sit-and-reach has t = -10.057, but P = 0.075, which is also implausible.

3. The authors state that they adjusted for age and BMI and then performed quadratic regression with PFI as the dependent variable and ABSI as the independent variable. However, the reported equations include only ABSI terms and an intercept. If age and BMI were adjusted, the regression equations should include these covariates, or the authors should clearly explain how adjustment was performed. The manuscript also does not provide regression coefficients, standard errors, 95% confidence intervals, P-values, or model diagnostics. Without these, the conclusion that the effect of ABSI on PFI is stronger in boys than girls are not adequately supported.

4. The study used stratified whole-group sampling from 6 middle schools and 6 high schools, with three classes selected from each grade, totaling 108 teaching classes. However, the analysis treats all students as independent observations. Because students are nested within classes and schools, standard errors and P-values may be biased if clustering is ignored. The authors should consider multilevel modeling, generalized estimating equations, or cluster-robust standard errors. At minimum, they should justify why clustering was not considered.

5. The manuscript defines ABSI as waist circumference divided by BMI^(2/3) × height^(1/2). HowePFI was calculated using Z-scores based on the 2014 China National Student Physical Fitness Survey, including grip strength, sit-and-reach, standing long jump, 50-m race, and endurance run. However, the manuscript does not provide the national reference means and standard deviations used for each age-sex group.ver, the units and calculation procedure are not sufficiently clear.

6. The manuscript should consistently use “a body shape index” rather than “a body size index,”.

7. Table 3 is too dense and difficult to read. The authors should simplify the table, move post-hoc pairwise comparisons to supplementary materials, and clearly state the correction method used for multiple comparisons.

8. Figure 3 shows extreme predicted PFI values at higher ABSI levels, especially in boys, which may reflect extrapolation beyond the observed data range. The authors should show the observed data distribution or restrict fitted curves to the observed ABSI range.

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Reviewers' comments:

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-->Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented. -->

Reviewer #1: Yes

Reviewer #2: Yes

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-->2. Has the statistical analysis been performed appropriately and rigorously? -->

Reviewer #1: Yes

Reviewer #2: Yes

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-->3. Have the authors made all data underlying the findings in their manuscript fully available?

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Reviewer #1: Yes

Reviewer #2: Yes

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-->4. Is the manuscript presented in an intelligible fashion and written in standard English?

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Reviewer #1: Yes

Reviewer #2: Yes

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-->5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)-->

Reviewer #1: the manuscript technically sound,statistical analysis has been performed appropriately,the data is clear but the way of collection needs to be provided ,and the manuscript presented is written in standard English

Reviewer #2: This is a commendable piece of research that tackles an important and contemporary issue in public health and physical education. The authors have gathered a compelling dataset, and the manuscript offers a meaningful contribution to the field. To elevate the quality of the paper to its full potential, I have raised a few specific queries regarding the methodology and operational definitions below.

Point 84. Reviewer Comment: Could the authors clarify whether validated methods or standardized criteria were employed to establish the selected study population? Please provide the relevant literature or bibliographical references supporting the sampling/selection strategy used.

Point 87. Reviewer Comment: For the sake of clarity and reproducibility, please provide a formal and explicitly cited definition of "chronic disease" as applied within the context of this study.

Point 90. Reviewer Comment: It is noted that certain questionnaires were deemed "valid." Could the authors explicitly define the exact inclusion and exclusion criteria used to evaluate the validity or completeness of the returned questionnaires?

Point 106. Reviewer Comment: Did the study protocol include a follow-up assessment to evaluate the recovery rate or time course of participants following the physical fitness tests? If so, please specify the timeline and parameters measured; if not, consider discussing this aspect as a potential direction for future research or as a limitation.

Point 111. Reviewer Comment: To improve the international readability of the manuscript, it would be highly beneficial to explicitly detail the specific methodologies and protocols utilized by the China

National Student Physical Fitness Survey. Providing a brief description or an appropriate reference would significantly help readers unfamiliar with this specific national framework.

I would like to thank the authors for their hard work and for submitting this research.

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Reviewer #1: Yes: ibrahim atta

Reviewer #2: No

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<p>The effect of a body shape index on physical fitness index is more pronounced in boys than in girls: evidence from a cross-sectional survey based on Tibetan adolescents aged 13-18 years in high-altitude areas of China

PONE-D-25-59844R1

Dear Dr. Liu,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

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Kind regards,

Zhanzhan Li

Academic Editor

PLOS One

Additional Editor Comments (optional):

Reviewers' comments: