Prevalence and Predictors of Musculoskeletal Pain in Recreational Resistance Trainers: Associations with Age, Gender, and Training History

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

There is confusion between weigthlifting, which is an olympic sport and weigthlifting in the gm. This must be clarifeid in the title and in the introduction. The participant can't be called weighlifters because this term identify a specific group of athlete.

Due that the participants are gym attenders, is not clear what time of actvity they did in the gym. This hamper significantly any conclusion.

the study focus on low back pain and this must be specified in the title and introduction.

There is no control group and is not specified with which data the results for each age category are compared. Which reference categories were used and , how the reference categegories were assessed ? Is not clear. If group A was used as a reference, what is the rationale for that ? Age ? Muscoloskeletal conditions ?

Numerosity for each age group is not reported.

What is the criteria for chosing those age categories ?

Where reside the novelty of the studies ? It is well known that gender, age and time of practice affect LBP. Where is a comparison with a normal population ?

The conclusion has nothing to do with the study, they are political reccomendation not suitable for a scientific paper. Conclusion must contain the scientific conclusion of the study. The same, in the introduction there are several statements about Kuwaiti politics and social causes for gym attendance that must be supported by references.

Overall, I reccomend to expand the study including control groups, to avoid statements not supported by previous data or references, and to keep the focus on science.

The paper need major revions before resubmission.

 

 

 

 

 

Author Response

Q1 There is confusion between weigthlifting, which is an olympic sport and weigthlifting in the gm. This must be clarifeid in the title and in the introduction. The participant can't be called weighlifters because this term identify a specific group of athlete.

 - We understand your concern, and while "recreational weightlifters" is acceptable and commonly used in sports science literature, we decided to change the term to recreational resistance trainers. We added the following sentence for clarification:

"Participants were classified as recreational resistance trainers, defined as individuals engaging in structured resistance exercise at least twice per week for general fitness purposes without competitive intent (8)."

 

Q 2 Due that the participants are gym attenders, is not clear what time of actvity they did in the gym. This hamper significantly any conclusion.

Thank you for the comment. We added the inclusion criteria more details for clarification.

Q 3 the study focus on low back pain and this must be specified in the title and introduction.

Thank you for the observation. We acknowledge the need to clarify the study's focus. Initially, the study aimed to describe the general pattern of musculoskeletal pain among recreational resistance trainers. However, after analyzing the frequency of reported pain sites, low back pain (LBP) was identified as the most prevalent complaint among participants. Based on this finding, we decided to focus the inferential analysis specifically on LBP using binary logistic regression

 

Q 4 There is no control group and is not specified with which data the results for each age category are compared. Which reference categories were used and , how the reference categegories were assessed ? Is not clear. If group A was used as a reference, what is the rationale for that ? Age ? Muscoloskeletal conditions ?

Thank you for your comment. We acknowledge that this study does not include a traditional control group. However, this design is intentional and appropriate for the research question, as the study aims to describe associations within a cross‑sectional sample of recreational resistance trainers, rather than to test the effect of an intervention or establish causality.

This study is observational and descriptive in nature, focusing on the distribution and predictors of low back pain (LBP) across age groups, gender, and training experience among individuals who regularly perform gym‑based resistance training.

A control group is not required for this type of analysis because we are not comparing a treatment versus no treatment or exposed versus unexposed condition in an interventional framework. Instead, we are assessing internal variation and risk factors within a defined population.

In relation to the reference category, In our model, categorical predictors (age group, gender, and history of practice) were entered using dummy coding, and one category for each variable was designated as the reference category against which the other groups were compared. The selection of reference categories was made based on standard practice, with the lowest or most common group used as the referent to facilitate meaningful interpretation of odds ratios.

We added more information in the methods to clarify the decision.

Q 5 Numerosity for each age group is not reported.

Thank you for your comment. We believe you are referring to the sample size distribution across age categories. This information has now been clearly added in Table 2, where the number of participants (n) in each age group is shown. We also refer to it explicitly in the METHODS Results section to ensure clarity..

Q 6 What is the criteria for chosing those age categories ?

Categorizing age into intervals is consistent with common practice in clinical and epidemiological research. Many studies group age into 10‑year bands or broader life-stage strata (e.g., young, middle-aged, older adults) when applying logistic regression models to account for potential nonlinear effects and improve interpretability. Similarly, research on low back pain frequently reports prevalence and risk estimates across defined age ranges rather than assuming a strictly linear association.

Q 7 Where reside the novelty of the studies ? It is well known that gender, age and time of practice affect LBP. Where is a comparison with a normal population ?

Thank you for the comment. As this is a descriptive cross-sectional study, no external control group was included. The focus is on characterizing associations within a specific and under-researched population: recreational resistance trainers in the GCC. Studies of this kind are rare in the region, and our findings contribute novel data on how age, gender, and training history relate to LBP within this context. Moreover, by describing a physically active population, the study offers useful insight into how regular gym-based training (≥2x/week) may be associated with lower musculoskeletal complaints, potentially reinforcing the role of structured exercise in prevention. More information was added in the introduction

Q 8 The conclusion has nothing to do with the study, they are political reccomendation not suitable for a scientific paper. Conclusion must contain the scientific conclusion of the study. The same, in the introduction there are several statements about Kuwaiti politics and social causes for gym attendance that must be supported by references.

We fully agree with this observation. The original conclusion included general public health recommendations that were not directly based on the study’s findings. We have revised the conclusion to reflect only the scientific insights drawn from our data. In addition, unsupported statements in the introduction related to political or social factors influencing gym attendance have been either removed or revised with appropriate references.

Q 9 Overall, I reccomend to expand the study including control groups, to avoid statements not supported by previous data or references, and to keep the focus on science.

Thank you for your recommendation. We acknowledge the value of including a control group and maintaining a strong scientific focus. As this is a descriptive cross-sectional study, no control group was included by design. However, we have revised the manuscript to remove unsupported claims and ensure that all conclusions and discussions remain strictly based on our data and relevant literature.

Reviewer 2 Report

Comments and Suggestions for Authors

This cross-sectional study examines the prevalence and distribution of musculoskeletal pain among recreational weightlifters in Kuwait using the Nordic Musculoskeletal Questionnaire and logistic regression analysis. The topic is relevant to injury prevention in recreational fitness populations and has potential public health implications. However, several methodological, analytical, and reporting issues substantially limit the interpretability and scientific contribution of the manuscript. Major revisions are required before the work can be considered for publication.

Major comments:

1. Lines 20–21; 136–137: The manuscript reports that data were collected from December 2023 to April 2025. This time frame extends into the future relative to the manuscript submission and raises questions about whether data collection has been completed and whether the dataset is finalized. The authors must clarify the actual study period and ensure that all dates are accurate and internally consistent.

2. Line 138 vs. Line 265: The Methods section states that participants exercised at least once per week (Line 138), whereas the Discussion states that participants exercised at least three times per week (Line 265). This inconsistency affects the definition of the study population and undermines methodological clarity. The authors should reconcile and clearly define the inclusion criteria.

3. Introduction, especially Lines 116–124: Although the Introduction provides broad background information, it does not clearly identify a specific research gap or state explicit research questions or hypotheses. The study appears primarily descriptive. The authors should clarify how their work extends existing literature and articulate specific, testable objectives.

4. The study does not quantify important training-related variables such as training volume, intensity, exercise type, supervision, technique quality, or prior injury history. Additionally, key demographic and health variables (e.g., BMI, occupation, comorbidities) are not considered. The absence of these variables likely contributes to residual confounding and limits interpretation of the regression model. These limitations should be explicitly acknowledged and discussed.

5. Lines 153–156; Table 2: The authors should justify the choice of reference categories in the logistic regression model and provide a clearer clinical interpretation of the resulting odds ratios. While the model is statistically significant, it explains a limited proportion of variance (Nagelkerke R² = 0.28), suggesting that important predictors may be missing. The authors should discuss model limitations and consider whether additional variables could improve explanatory power.

6. Line 183: The chi-square statistic is presented with formatting errors (e.g., duplicated notation). Statistical reporting should be corrected and standardized throughout the manuscript.

7. The main findings—that older participants and those with longer training histories report more musculoskeletal pain—are largely consistent with prior literature. The manuscript should better articulate its novel contribution and explain how the findings advance understanding beyond existing studies.

8. The Nordic Musculoskeletal Questionnaire captures the presence or absence of symptoms but does not measure pain intensity, duration, or functional impact. This limitation should be explicitly acknowledged, and its implications for interpreting prevalence estimates should be discussed.

9. Lines 200–270: The Discussion largely reiterates known information and does not sufficiently integrate the current findings into a broader conceptual framework. Additionally, the Conclusions recommend intervention strategies that were not directly evaluated in the study. The authors should align their conclusions more closely with the study design and results.

10. The manuscript does not report key logistic regression diagnostics. The authors should clarify: (1) whether multicollinearity was assessed, (2) how model fit beyond the omnibus test was evaluated (e.g., Hosmer–Lemeshow test), (3) whether influential observations were examined, and (4)how missing data were handled.

11. Age and years of practice are categorized into broad groups. Categorizing continuous variables can reduce statistical power and obscure dose–response relationships. The authors should justify their categorization strategy or consider sensitivity analyses using continuous predictors.

12. Although odds ratios and confidence intervals are reported, interpretation remains limited. The authors should emphasize effect sizes and clinical relevance rather than relying primarily on p-values.

Minor comments:

13. Several grammatical and typographical errors are present and should be corrected through careful language editing.

14. Table and figure captions should be more descriptive and self-contained.

15. Terminology related to musculoskeletal symptoms and injuries should be used consistently.

16. Ethical approval and institutional review board information should be presented clearly and consistently.

17. Some references appear duplicated or inconsistently formatted and should be checked for accuracy.

Author Response

This cross-sectional study examines the prevalence and distribution of musculoskeletal pain among recreational weightlifters in Kuwait using the Nordic Musculoskeletal Questionnaire and logistic regression analysis. The topic is relevant to injury prevention in recreational fitness populations and has potential public health implications. However, several methodological, analytical, and reporting issues substantially limit the interpretability and scientific contribution of the manuscript. Major revisions are required before the work can be considered for publication.

Major comments:

Q 1. Lines 20–21; 136–137: The manuscript reports that data were collected from December 2023 to April 2025. This time frame extends into the future relative to the manuscript submission and raises questions about whether data collection has been completed and whether the dataset is finalized. The authors must clarify the actual study period and ensure that all dates are accurate and internally consistent.

Thank you for your comment. The data collection period (Dec 2023–Apr 2025) is correct. As the manuscript was submitted in January 2026, the dataset used is complete and finalized. If this is not the problem, please let me know

 

Q 2. Line 138 vs. Line 265: The Methods section states that participants exercised at least once per week (Line 138), whereas the Discussion states that participants exercised at least three times per week (Line 265). This inconsistency affects the definition of the study population and undermines methodological clarity. The authors should reconcile and clearly define the inclusion criteria.

Thank you for your comment. The correct inclusion criterion was exercising at least two times per week. We have corrected the inconsistency in the Methods and Discussion sections to reflect this accurately.

Q3. Introduction, especially Lines 116–124: Although the Introduction provides broad background information, it does not clearly identify a specific research gap or state explicit research questions or hypotheses. The study appears primarily descriptive. The authors should clarify how their work extends existing literature and articulate specific, testable objectives.

Thank you for your suggestion. We revised the Introduction to better define the research gap and clarify the study objective. While the study is descriptive, it addresses a population underrepresented in the literature—recreational resistance trainers in the Middle East—and examines how age, gender, and training experience relate to low back pain in this context. The revised text now states the objective explicitly and frames it within existing research.

Q 4. The study does not quantify important training-related variables such as training volume, intensity, exercise type, supervision, technique quality, or prior injury history. Additionally, key demographic and health variables (e.g., BMI, occupation, comorbidities) are not considered. The absence of these variables likely contributes to residual confounding and limits interpretation of the regression model. These limitations should be explicitly acknowledged and discussed.

We appreciate observation. We acknowledge that variables such as training volume, intensity, exercise type, supervision, technique quality, and prior injury history—as well as additional demographic and health factors like BMI, occupation, and comorbidities—were not collected in this study. This limitation may indeed contribute to residual confounding and restrict the precision of the regression analysis. We have now included a dedicated limitations paragraph in the discussion to transparently address these gaps and contextualize our findings.

Q 5. Lines 153–156; Table 2: The authors should justify the choice of reference categories in the logistic regression model and provide a clearer clinical interpretation of the resulting odds ratios. While the model is statistically significant, it explains a limited proportion of variance (Nagelkerke R² = 0.28), suggesting that important predictors may be missing. The authors should discuss model limitations and consider whether additional variables could improve explanatory power.

Thank you for your observation. In relation to the reference category, In our model, categorical predictors (age group, gender, and history of practice) were entered using dummy coding, and one category for each variable was designated as the reference category against which the other groups were compared. The selection of reference categories was made based on standard practice, with the lowest or most common group used as the referent to facilitate meaningful interpretation of odds ratios. We have also added clinical interpretations of the odds ratios in the Discussion section to improve clarity.

We agree that the Nagelkerke R² value of 0.28 indicates that other relevant predictors—such as BMI, previous injury, intensity or type of training—were not included in the model, limiting its explanatory power. This limitation is now acknowledged in the Limitations section, and we emphasize the need for future studies to incorporate these variables to enhance model performance.

Q 6. Line 183: The chi-square statistic is presented with formatting errors (e.g., duplicated notation). Statistical reporting should be corrected and standardized throughout the manuscript.

Thank you for highlighting this issue. The duplication and formatting inconsistency of the chi-square statistic were noted. We have corrected the statistical notation throughout the manuscript to follow MDPI and journal style guidelines

Q7: The main findings—that older participants and those with longer training histories report more musculoskeletal pain—are largely consistent with prior literature. The manuscript should better articulate its novel contribution and explain how the findings advance understanding beyond existing studies.

The focus is on characterizing associations within a specific and under-researched population: recreational resistance trainers in the GCC. Studies of this kind are rare in the region, and our findings contribute novel data on how age, gender, and training history relate to LBP within this context. Moreover, by describing a physically active population, the study offers useful insight into how regular gym-based training (≥2x/week) may be associated with lower musculoskeletal complaints, potentially reinforcing the role of structured exercise in prevention. More information was added in the introduction

Q 8. The Nordic Musculoskeletal Questionnaire captures the presence or absence of symptoms but does not measure pain intensity, duration, or functional impact. This limitation should be explicitly acknowledged, and its implications for interpreting prevalence estimates should be discussed.

Thank you for this observation. We agree with the limitation of the NMQ, which captures only the presence or absence of symptoms but not pain intensity, duration, or functional consequences. We have now included a sentence in the limitations paragraph acknowledging this and clarifying its implications for the interpretation of prevalence estimates.

Q 9. Lines 200–270: The Discussion largely reiterates known information and does not sufficiently integrate the current findings into a broader conceptual framework. Additionally, the Conclusions recommend intervention strategies that were not directly evaluated in the study. The authors should align their conclusions more closely with the study design and results.

We agree with the reviewer’s observation and have revised both the Discussion and Conclusion sections to ensure alignment with the study design and findings.

10. The manuscript does not report key logistic regression diagnostics. The authors should clarify: (1) whether multicollinearity was assessed, (2) how model fit beyond the omnibus test was evaluated (e.g., Hosmer–Lemeshow test), (3) whether influential observations were examined, and (4)how missing data were handled.

A new paragraph in data analysis was written to clarify the procedures.

Q 11. Age and years of practice are categorized into broad groups. Categorizing continuous variables can reduce statistical power and obscure dose–response relationships. The authors should justify their categorization strategy or consider sensitivity analyses using continuous predictors.

Thank you for this important point. We categorized age and training history to reflect nonlinear associations with low back pain and to enhance interpretability across life stages and experience levels. This approach is commonly used in epidemiological studies where risk does not vary linearly with age (e.g., Béland et al., 2023). Categorization also improves clarity in reporting odds ratios. We have clarified this rationale in the Methods section.

     (Beller, J., & Epping, J. (2022). Trends in activity limitations from an international perspective. European Journal of Public Health, e1–e8. https://doi.org/10.1093/eurpub/ckac174)

Q 12. Although odds ratios and confidence intervals are reported, interpretation remains limited. The authors should emphasize effect sizes and clinical relevance rather than relying primarily on p-values.

The discussion was revised, we hope that now it aligns with the expectations.

Minor comments:

13. Several grammatical and typographical errors are present and should be corrected through careful language editing.

revised

14. Table and figure captions should be more descriptive and self-contained.

revised

15. Terminology related to musculoskeletal symptoms and injuries should be used consistently.

revised

Q 16. Ethical approval and institutional review board information should be presented clearly and consistently.

revised

17. Some references appear duplicated or inconsistently formatted and should be checked for accuracy.

revised

 

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors modified the paper accordingly to some reviewer's
suggestions. However, it remain a significant problem : the absence of a control group (that can be of different nature: e.g. professional weight lifters or subjects practicing a different sport or moderately active (especially in an older age).
.  
Also,  the reason for chosing the indicated cut-off points for stratification are not clear: why did you chose those sepcific cut-off ages ? please explain.  In the statistical part are missing informations about the distribution of the data (e.g. normality). Even if this is not mandatory for a regression, this point is very important in making the result more meaningfull.

Author Response

1) The authors modified the paper accordingly to some reviewer's suggestions. However, it remain a significant problem : the absence of a control group (that can be of different nature: e.g. professional weight lifters or subjects practicing a different sport or moderately active (especially in an older age).

We thank the reviewer for this important comment. We respectfully clarify that the absence of a control group is consistent with the observational and descriptive cross-sectional design of the present study. Our objective was not to compare recreational resistance trainers with another population (e.g., non-exercisers, athletes, or different sport groups), but rather to examine the prevalence and predictors of musculoskeletal pain within a defined population of recreational resistance trainers. In practical terms, the study aims to answer the question: “Among individuals who regularly perform resistance training, how do age, gender, and years of practice relate to the likelihood of reporting musculoskeletal pain?” rather than whether this group has higher or lower risk than non-exercising individuals.

Importantly, the use of a single-population design without a control group is common in studies applying the Nordic Musculoskeletal Questionnaire (NMQ) and in research focusing on physically active or occupational populations. For example, Kuorinka et al. (1987) developed the NMQ specifically for epidemiological surveillance within defined populations, and subsequent studies in workers, athletes, and training populations (e.g., Besharati, 2020; Ilaria et al., 2019) have similarly used cross-sectional designs without external control groups while analyzing prevalence and associated factors through regression models. This methodological approach is therefore consistent with established practice in musculoskeletal epidemiology.

Additionally, we note that other reviewers did not raise concerns regarding the absence of a control group, and their feedback primarily focused on clarity of methodology, statistical reporting, and interpretation, which have been thoroughly revised. While including comparison groups such as non-exercisers or elite athletes could be valuable for future research, it would address a different research question and require a distinct study design. The present study intentionally focuses on characterizing musculoskeletal pain patterns and predictors within an understudied population—recreational resistance trainers in Kuwait—rather than conducting between-group risk comparisons.

 
2) Also,  the reason for chosing the indicated cut-off points for stratification are not clear: why did you chose those sepcific cut-off ages ? please explain.  In the statistical part are missing informations about the distribution of the data (e.g. normality). Even if this is not mandatory for a regression, this point is very important in making the result more meaningfull.

Thank you for this important comment. The age cut-off points were defined a priori to create meaningful strata and ensure sufficient numerosity within each category for stable comparisons in the logistic regression analysis. This stratification approach is consistent with epidemiological and Nordic Musculoskeletal Questionnaire (NMQ)-based studies, where demographic variables such as age are commonly grouped to facilitate subgroup analysis and interpretation of prevalence and risk patterns (Kuorinka et al., 1987).

Furthermore, the purpose of stratification in this study is primarily interpretative rather than inferential. From a practical perspective, the grouped analysis allows readers and practitioners to easily identify their corresponding age category and directly interpret the associated odds of musculoskeletal pain within that subgroup. In other words, the categorization enhances clinical and practical readability of the results, rather than materially altering the underlying associations. Importantly, the main conclusions of the study are driven by the overall regression patterns, and not dependent on any single cut-off point, as the stratification serves as a tool for clearer subgroup comparison within a recreational resistance training population.

In relation to normality,  We acknowledge that normality of data distribution was not assessed. However, as the primary analysis used binary logistic regression with categorical predictors (age group, gender, and training history) and a binary outcome (LBP), the assumption of normality is not required for this type of model. Logistic regression does not rely on normally distributed variables, but rather on correct model specification, absence of multicollinearity, and adequate model fit, which were assessed and are now clarified in the statistical analysis section. One sentence was added in the methods.

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have made substantial improvements to the manuscript and have addressed most of the methodological and statistical concerns raised in the previous review. The inclusion criteria are now clarified, the research objective is more clearly articulated, additional regression diagnostics have been reported, and the limitations section has been meaningfully expanded. Overall, the manuscript is considerably strengthened. However, a few remaining issues require correction before the manuscript could be accepted:

1. The manuscript states that 645 participants were included, but the Methods section indicates that 642 completed the survey. These numbers must be reconciled and consistently reported throughout the manuscript.

2. The Methods section refers to both four age groups and “five predefined age groups.” This inconsistency should be corrected to ensure clarity and internal consistency.

3. The Conclusions section refers to participants with “more than 10 years” of training experience, whereas the analysis categorizes training history as “>5 years.” This appears to be an error and must be corrected.

4. The individualized risk estimate presented in the Discussion should be clarified to avoid potential overinterpretation of model-derived probabilities.

Author Response

1. The manuscript states that 645 participants were included, but the Methods section indicates that 642 completed the survey. These numbers must be reconciled and consistently reported throughout the manuscript.
2. The Methods section refers to both four age groups and “five predefined age groups.” This inconsistency should be corrected to ensure clarity and internal consistency.

We thank the reviewer for the very careful reading of the manuscript. We have revised the text to reconcile the reported sample size and to ensure consistency between the number of participants included and those who completed the survey. In addition, the description of the age stratification has been corrected throughout the Methods and Results sections to consistently reflect the use of four predefined age groups. These inconsistencies were due to editing under a tight revision timeline and have now been carefully checked and harmonized across the manuscript

3. The Conclusions section refers to participants with “more than 10 years” of training experience, whereas the analysis categorizes training history as “>5 years.” This appears to be an error and must be corrected.

Also revised

4. The individualized risk estimate presented in the Discussion should be clarified to avoid potential overinterpretation of model-derived probabilities.

Thank you for this important comment. We agree that the individualized risk example could be misinterpreted as a precise prediction. We have revised the Discussion paragraph to clarify that the reported probability is a model-derived estimate intended for illustrative purposes only, based on the observed associations within the sample. We now explicitly state that these probabilities should not be interpreted as exact individual risk predictions, but rather as descriptive indications of relative likelihood within the study population, given the cross-sectional design and the limited set of predictors included in the model.