Effects of Integrating Wearable Resistance into Regular Volleyball Training on Countermovement Jump Performance and Kinematics During the In-Season Period

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Abstract

1. Improve the last part of the abstract. It ends with a result and the conclusion and the practical application or implications of the findings are missing.

Introduction

2. End of second paragraph. Could you include any examples of jumping improvements in adults? In the case of children, physical development can play an important role in improvements in jumping ability.
3. What is known about this topic in relation to injuries? What is the maximum load that should be used? Could it put excessive strain on the joints? Please include some information about this in the introduction (I have seen that you have mentioned something in the methodology).

Methods

4. The methodology states the following:

In this study, players did not engage in any dedicated plyometric training. Instead, wearable resistance (WR) was incorporated into parts of their regular volleyball training. Therefore, this was not a study of WR use in plyometric training, but rather an investigation of how WR, when used as part of general training, influences performance such as counter movement jump.

I have not seen in the introduction, studies that have done something similar... Could they be included? This methodology should be made clear in the title of the paper. For example the title could be something like this (improving it): Effect of including additional weights in regular volleyball training on jump performance and kinematics in volleyball players.

5. What does the 6 refer to in this sentence? To examine this, 16 female volleyball players participated in an eight-week randomized controlled 6 pretest-posttest study
6. Why were forearm weights put on the forearms of the control group? Wouldn't it be better to have no weights at all? I suppose the weight will be mentioned later.
7. Explain a little about what the motoric/technical sessions consist of.
8. Explain a bit better how the analysis was done with Gpower (provide more details about it). Just say what kind of test family was used in Gpower and simplify a bit the percentage of improvement (there is too much information):

Based on the analysis, a sample size of 6 participants per group was needed to achieve a power level of 0.90. This calculation was based on the expected effect size, derived from an anticipated 2.5% improvement in jump performance over an 8-week pe-riod, and the within-group variance observed in pre-test jump performance measure-ments. Anticipated improvement of 2.5% derived from previous studies that showed jump performance stagnate or even decline during the competitive season, with observed decreases of approximately 5.4% or minimal improvements of around 3.9%, even with continued strength and plyometric training [7, 8]. Given this context, a conservative an-ticipated improvement of 2.5% was selected, reflecting realistic expectations and difficul-ties of enhancing performance in the competitive season. This sample size and power level were chosen to maximize the sensitivity of the study in detecting expected performance improvements, thereby minimizing the likelihood of a Type II error.

9. Indicate the rest times between jumps in the following paragraph:

The larger number of jumps in the pre-test was intended to allow for familiarization with the testing setup and to account for natural variability in performance. From the eight pre-test jumps, the highest five were selected and used for analysis, while all five post-test jumps were included, as participants were already famil-iar with the procedure. For kinematic analysis, only the single best jump (based on maxi-mal jump height) was selected from both the pre- and post-test trials. This approach en-sured that movement mechanics were compared using the highest-effort performances.

10. Justify the following procedure with a reference:

The resistance was introduced progressively, starting with 100g per leg and increasing by 100g every two weeks, reaching 400g per leg by the end of the intervention (Figure 2).

11. I still don't understand why the control group wore weights on their forearms. That extra weight also affects the muscles in the lower limbs. I think it would have been better not to include weights on the forearms. It seems that the authors were looking to improve spiking speed and that this procedure was unrelated to the objective of this research.

The control group served as an active control group, wearing the WR sleeves (Lila™) on their forearms (Figure 1) to ensure a comparable external load without directly affecting lower-limb mechanics. Quizás los autores puede hablar de os efectos de la diferente localización del peso adicional en el rendimiento (salto o remate). ¿Midieron por ejemplo la cinemática del remate o algún parámetro relacionado con el rendimiento del remate como la velocidad de la pelota?

12. Only with the flight time variable the jump height can be calculated, the contact time is not necessary:

An Infrared Optical Contact Grid (Musclelab, Ergotest Innovation AS, Norway) was used to measure jump height, which measured flight time and contact time to calculate countermovement jump (CMJ) height.

13. Are you sure that this procedure is correct?

Joint angular velocities were then calculated using a 5-point numerical differentiation filter applied to these angular measures.

I'm just asking, I remember reading a document that stated that angular velocity is not calculated by differentiating the angle, as is the case with displacement and linear velocity. Take a look at this reference, for example:

Joint angular velocities were then calculated as the angular velocity vectors using the corresponding cardan angles.

Namiki, Y., Sano, Y., Makimoto, A., Hashizume, S., Murai, A., Kobayashi, Y., ... & Hobara, H. (2017). Joint moments of unilateral transfemoral amputees using running-specific prosthesis during sprinting. ISBS Proceedings Archive, 35(1), 234.

If the procedure is correct, details of the filter used (Butterworth filter?) should be given.

14. I do not understand why they have included the following statistical procedure in the data analysis part. Explanations are repeated in these two sections.

Paired-samples t-tests were used to assess pre- to post-test changes within each group (WR and No-WR), and change scores (Post – Pre) were compared between groups using independent samples t-tests.

Results

15. They seem correct but in my opinion they can be synthesised and simplified.

Discussion

16. Include some additional explanation, e.g. related to increased recruitment of muscle fibres or talk about post-activation potentiation or contrast-based training (could partly explain improvements in jumping).
17. Could you come up with a biomechanical explanation and not just based on instrument error?

To better understand why large effect sizes did not translate into statistically significant changes, movement phases were analyzed. Interestingly, for two of the athletes who jumped higher, measured CoM velocity decreased, a contradiction of basic kinematic principles. This anomaly suggests potential inaccuracies in measurement systems. While the Xsens MVN Link is suitable for field-based motion capture, it relies on IMUs, which are prone to errors such as drift, sensor misalignment and movement, especially during high-speed actions like jumping [13]. These limitations may have concealed real changes in performance, leading to the lack of statistically significant findings despite meaningful individual improvements.

18. Include a section on future lines of action and limitations.

Conclusions

19. As I said at the beginning of this letter you should look for a different term to make it clear that this is not specific training but the use of additional weight during the training itself.

This study investigated the effects of an eight-week wearable resistance training program on countermovement jump performance and kinematics in experienced female volleyball players during the in-season period.

Author Response

We want to thank the reviewer for the comments. We have answered to all the comments the reviewer raised and think that the manuscript now is suitable for publication. Changes in the manuscript are collored in red.

Abstract

1. Improve the last part of the abstract. It ends with a result and the conclusion and the practical application or implications of the findings are missing.

• Response: We thank the reviewer for this helpful suggestion. In the revised abstract we added a final sentence to highlight the practical implications of our findings

Introduction

1. End of second paragraph. Could you include any examples of jumping improvements in adults? In the case of children, physical development can play an important role in improvements in jumping ability.

• Response: The Introduction already includes an example of adults: “female soccer players aged 16–20 demonstrated gains of around 17.6% in jump height after an 8-week plyometric training intervention.” This highlights that jump improvements in adults are achievable, though often smaller than those reported in youth populations.

 

1. What is known about this topic in relation to injuries? What is the maximum load that should be used? Could it put excessive strain on the joints? Please include some information about this in the introduction (I have seen that you have mentioned something in the methodology).

• Response: We agree with the reviewer that injury risk is an important consideration, although it was not the focus of this study. To address this, we have clarified in the Introduction that the loads applied here were very small (<2% body mass) and introduced progressively, making them unlikely to cause excessive joint strain. Furthermore, the current literature on wearable resistance and injury risk is very limited, and clear guidelines on maximum safe loads have not yet been established.

Methods

1. The methodology states the following:

In this study, players did not engage in any dedicated plyometric training. Instead, wearable resistance (WR) was incorporated into parts of their regular volleyball training. Therefore, this was not a study of WR use in plyometric training, but rather an investigation of how WR, when used as part of general training, influences performance such as counter movement jump.

I have not seen in the introduction, studies that have done something similar... Could they be included? This methodology should be made clear in the title of the paper. For example the title could be something like this (improving it): Effect of including additional weights in regular volleyball training on jump performance and kinematics in volleyball players.

• Response: We appreciate the reviewer’s point. To clarify the novelty of our approach, we revised the Introduction to state that this study examined the integration of wearable resistance directly into regular volleyball training sessions, rather than as a separate program. In addition, we have modified the title to: “Effects of Integrating Wearable Resistance into Regular Volleyball Training on Countermovement Jump Performance and Kinematics During the In-Season Period” This makes clear that WR was integrated into regular practice, not performed as an independent training program.

1. What does the 6 refer to in this sentence? To examine this, 16 female volleyball players participated in an eight-week randomized controlled 6 pretest-posttest study

• Response: We thank the reviewer for noticing this error. The “6” was a typographical mistake and has been removed.

 

1. Why were forearm weights put on the forearms of the control group? Wouldn't it be better to have no weights at all? I suppose the weight will be mentioned later.

• Response: We thank the reviewer for raising this point. The control group was assigned forearm-mounted weights to create an active control condition. This ensured that both groups trained with external load, while isolating the specific effect of calf-mounted WR on jump performance. Using forearm weights also helped reduce potential placebo or Hawthorne effects, since both groups experienced wearing WR during training.

 

1. Explain a little about what the motoric/technical sessions consist of.

• Response: We have clarified in the Methods that these sessions emphasized both individual skills and 1-on-1 plays (technical focus), as well as dynamic group-based drills (motoric focus), reflecting the team’s normal in-season training structure. These sessions were part of the standard team program and were not modified for the purposes of this study.

 

1. Explain a bit better how the analysis was done with Gpower (provide more details about it). Just say what kind of test family was used in Gpower and simplify a bit the percentage of improvement (there is too much information):

• Response: The description has been simplified: we now state that an a priori power analysis was conducted in G*Power 3.1.9.7 [12], using the F-test family (ANOVA: repeated measures, within–between interaction) with α = 0.05 and power (1–β) = 0.90. Variance estimates (effect = 1.6, within-group = 0.56) indicated that a minimum of 6 participants was sufficient, and our final sample of 13 exceeded this requirement.

Based on the analysis, a sample size of 6 participants per group was needed to achieve a power level of 0.90. This calculation was based on the expected effect size, derived from an anticipated 2.5% improvement in jump performance over an 8-week pe-riod, and the within-group variance observed in pre-test jump performance measure-ments. Anticipated improvement of 2.5% derived from previous studies that showed jump performance stagnate or even decline during the competitive season, with observed decreases of approximately 5.4% or minimal improvements of around 3.9%, even with continued strength and plyometric training [7, 8]. Given this context, a conservative an-ticipated improvement of 2.5% was selected, reflecting realistic expectations and difficul-ties of enhancing performance in the competitive season. This sample size and power level were chosen to maximize the sensitivity of the study in detecting expected performance improvements, thereby minimizing the likelihood of a Type II error.

1. Indicate the rest times between jumps in the following paragraph:

• Response: We have now clarified in the Methods (Section 2.3, Testing Procedures) that rest periods of approximately 30–45 seconds were provided between jump attempts to minimize fatigue and ensure consistent effort.

The larger number of jumps in the pre-test was intended to allow for familiarization with the testing setup and to account for natural variability in performance. From the eight pre-test jumps, the highest five were selected and used for analysis, while all five post-test jumps were included, as participants were already famil-iar with the procedure. For kinematic analysis, only the single best jump (based on maxi-mal jump height) was selected from both the pre- and post-test trials. This approach en-sured that movement mechanics were compared using the highest-effort performances.

1. Justify the following procedure with a reference:

The resistance was introduced progressively, starting with 100g per leg and increasing by 100g every two weeks, reaching 400g per leg by the end of the intervention (Figure 2).

• Response: We thank the reviewer for this comment. The progressive loading approach was chosen to ensure safety and allow gradual adaptation during the competitive season. While the literature on optimal WR progression is limited, we clarified in the Methods that the loads used here represented <2% of body mass, which is well below thresholds typically considered safe. We have noted this rationale in the revised text.

1. I still don't understand why the control group wore weights on their forearms. That extra weight also affects the muscles in the lower limbs. I think it would have been better not to include weights on the forearms. It seems that the authors were looking to improve spiking speed and that this procedure was unrelated to the objective of this research.

• Response: The control group was assigned forearm-mounted WR to serve as an active control condition, ensuring that both groups experienced wearing WR and trained under similar external load conditions. This approach reduced potential placebo or Hawthorne effects, while isolating the local effects of calf-mounted WR on jump performance. Although forearm loading can influence upper-body mechanics, we selected this placement because it does not directly target the lower-limb musculature responsible for vertical jump performance. We agree that examining the effects of forearm WR on spiking kinematics and ball velocity would be valuable, but this was beyond the scope of the present study. We have added this point to the “Future Studies” section to highlight it as an avenue for further research.

The control group served as an active control group, wearing the WR sleeves (Lila™) on their forearms (Figure 1) to ensure a comparable external load without directly affecting lower-limb mechanics. Quizás los autores puede hablar de os efectos de la diferente localización del peso adicional en el rendimiento (salto o remate). ¿Midieron por ejemplo la cinemática del remate o algún parámetro relacionado con el rendimiento del remate como la velocidad de la pelota?

1. Only with the flight time variable the jump height can be calculated, the contact time is not necessary:

• Response: We thank the reviewer for this observation. We have simplified the Methods description accordingly and now state that jump height was calculated from flight time only.

An Infrared Optical Contact Grid (Musclelab, Ergotest Innovation AS, Norway) was used to measure jump height, which measured flight time and contact time to calculate countermovement jump (CMJ) height.

1. Are you sure that this procedure is correct?

• Response: Yes, in our analysis, joint angular velocities were derived from Euler angles in three dimensions by applying a five-point numerical differentiation filter. This approach is standard in biomechanical research and has been applied in several previous studies. Given this, we are confident that our procedure is correct.

Joint angular velocities were then calculated using a 5-point numerical differentiation filter applied to these angular measures.

I'm just asking, I remember reading a document that stated that angular velocity is not calculated by differentiating the angle, as is the case with displacement and linear velocity. Take a look at this reference, for example:

Joint angular velocities were then calculated as the angular velocity vectors using the corresponding cardan angles.

Namiki, Y., Sano, Y., Makimoto, A., Hashizume, S., Murai, A., Kobayashi, Y., ... & Hobara, H. (2017). Joint moments of unilateral transfemoral amputees using running-specific prosthesis during sprinting. ISBS Proceedings Archive, 35(1), 234.

If the procedure is correct, details of the filter used (Butterworth filter?) should be given.

1. I do not understand why they have included the following statistical procedure in the data analysis part. Explanations are repeated in these two sections.

• Response: We thank the reviewer for the observation. To clarify, the two t-tests served different purposes in our analysis: paired-samples t-tests were used to examine pre–post changes within each group, while independent-samples t-tests were used to compare between-group change scores. These were therefore not repetitions but complementary analyses addressing different aspects of the data.

Paired-samples t-tests were used to assess pre- to post-test changes within each group (WR and No-WR), and change scores (Post – Pre) were compared between groups using independent samples t-tests.

Results

1. They seem correct but in my opinion they can be synthesised and simplified.

• Response: We thank the reviewer for confirming that the results are correct. We prefer to retain the current level of detail, as it ensures clarity and transparency in presenting the findings. This also helps readers fully understand the analyses and how the results align with the discussion. For these reasons, we believe the existing presentation is the most appropriate.

Discussion

1. Include some additional explanation, e.g. related to increased recruitment of muscle fibres or talk about post-activation potentiation or contrast-based training (could partly explain improvements in jumping).

• Response: We thank the reviewer for this suggestion. We agree that neuromuscular mechanisms such as fibre recruitment may contribute to improvements in jump performance. Since these were not directly measured in the present study, we cannot provide evidence-based discussion of them. However, we already note in the “Future Studies” section that incorporating direct measures of neuromuscular adaptation would help clarify the mechanisms behind performance changes. We therefore believe this point is addressed in the current version of the manuscript.

 

1. Could you come up with a biomechanical explanation and not just based on instrument error?

• Response: We thank the reviewer for this observation. In the original version, we emphasized the limitations of IMU-based motion capture as a possible explanation for the discrepancy between increased jump height and unchanged or decreased CoM velocity. We agree that biomechanical factors could also contribute. We have therefore revised the Discussion to note that improvements in the efficiency of the eccentric–concentric transition (stretch–shortening cycle) or subtle changes in arm swing and trunk coordination may enhance jump height without producing large measurable increases in peak CoM velocity.

To better understand why large effect sizes did not translate into statistically significant changes, movement phases were analyzed. Interestingly, for two of the athletes who jumped higher, measured CoM velocity decreased, a contradiction of basic kinematic principles. This anomaly suggests potential inaccuracies in measurement systems. While the Xsens MVN Link is suitable for field-based motion capture, it relies on IMUs, which are prone to errors such as drift, sensor misalignment and movement, especially during high-speed actions like jumping [13]. These limitations may have concealed real changes in performance, leading to the lack of statistically significant findings despite meaningful individual improvements.

1. Include a section on future lines of action and limitations.

• Response: A section on future directions is already included under “Practical Applications and Future Studies,” and the study limitations are discussed at the end of the Discussion.

Conclusions

1. As I said at the beginning of this letter you should look for a different term to make it clear that this is not specific training but the use of additional weight during the training itself.

This study investigated the effects of an eight-week wearable resistance training program on countermovement jump performance and kinematics in experienced female volleyball players during the in-season period.

• Response: We agree with the reviewer. The Conclusion has been revised to emphasize that WR was integrated into regular volleyball training sessions rather than implemented as a separate training program. This change, together with the updated title, ensures consistency and avoids any misunderstanding of the intervention design.

Reviewer 2 Report

Comments and Suggestions for Authors

This study investigates the effects of an eight-week, in-season wearable resistance(WR) training program through the countermovement jump (CMJ) performance and kinematics of experienced female volleyball players. The research addresses the practical challenge of maintaining or improving explosive power during a competitive season, a period often associated with performance plateaus or declines. The key finding was that the calf-wearable resistance group demonstrated a statistically significant and meaningful improvement in CMJ height by 9.5% compared to the control group. It is meaningful study that the effect of WR was resulted in improvement of CMJ by experienced volleyball players. However, I would suggest these corrections as below for the higher scientific consistency.

 

1) In section 2.5 Measurement, the joint angular velocities were calculated using a 5-point numerical differentiation filter applied to these angular measures. But, there were no significant difference in angular velocity between invention group and the control group. Then, I suggest to adjust the filtering on the measured angle using the Xsens motion capture system, e.g. using 3- or 7-point of numerical differentiation.

 

2) In page 6, the authors attempted kinematic analysis for the date of highest jump. However, difference in angular velocity might be found in the second, third, or fourth highest jump.

 

3) In the experiment, the weight of 100g per leg, and increasing 100g every two weeks was applied. However, more important than the 100g itself is the ratio of 100g/body weight. Please add that value.

 

4) When using abbreviations, the first instance of a term should be its full name (abbreviation), and subsequent uses should be the abbreviation. This consistency is lacking. For example, please review 'countermovement jumps (CMJ)' on page 6.

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Author Response

We want to thank the reviewer for the comments. We have answered to all the comments the reviewer raised and think that the manuscript now is suitable for publication. Changes in the manuscript are collored in red.

This study investigates the effects of an eight-week, in-season wearable resistance(WR) training program through the countermovement jump (CMJ) performance and kinematics of experienced female volleyball players. The research addresses the practical challenge of maintaining or improving explosive power during a competitive season, a period often associated with performance plateaus or declines. The key finding was that the calf-wearable resistance group demonstrated a statistically significant and meaningful improvement in CMJ height by 9.5% compared to the control group. It is meaningful study that the effect of WR was resulted in improvement of CMJ by experienced volleyball players. However, I would suggest these corrections as below for the higher scientific consistency.

• In section 2.5 Measurement, the joint angular velocities were calculated using a 5-point numerical differentiation filter applied to these angular measures. But, there were no significant difference in angular velocity between invention group and the control group. Then, I suggest to adjust the filtering on the measured angle using the Xsens motion capture system, e.g. using 3- or 7-point of numerical differentiation.
• Response: We appreciate the suggestion. The 5-point differentiation method we used is a standard way to calculate velocities in biomechanics as it balances accuracy with noise reduction. Differentiation always increases noise, and multi-point methods are widely applied to address this. Importantly, validation studies show that Xsens provides reliable kinematic data when combined with these kinds of processing methods (Al-Amri et al., 2018; Nijmeijer et al., 2023). For this reason, we are confident that our approach was appropriate, and using a 3- or 7-point method would not have changed the results in a meaningful way.
• In page 6, the authors attempted kinematic analysis for the date of highest jump. However, difference in angular velocity might be found in the second, third, or fourth highest jump.
• Response: We understand the concern. To clarify, this was not decided after the fact, in Methods 2.3 we already stated that kinematic analysis would be performed on the highest jump. Our reasoning is that the study focused on peak performance, and in sports science it’s common practice to take the best trial (fastest sprint, highest jump, heaviest lift) as the key outcome when testing maximal ability. We agree that averaging several top trials can also be useful, but reliability research shows that both approaches give very similar results. For example, Petré et al. (2023) reported that jump outcomes are just as reliable whether you use the best single jump or the average of the top two or three. Based on this, we believe analyzing the best jump was a fair and defensible choice.
• In the experiment, the weight of 100g per leg, and increasing 100g every two weeks was applied. However, more important than the 100g itself is the ratio of 100g/body weight. Please add that value.
• Response: We agree with the reviewer. In Methods 2.2 we reported that participants had an average body mass of 66.8 ± 6.9 kg. Based on this, the progression of wearable resistance represented approximately 0.15%, 0.30%, 0.45%, and 0.60% of body mass at each two-week stage. We added this information to the manuscript. If individual body masses are available, we will also provide the range of relative loads across participants.
• When using abbreviations, the first instance of a term should be its full name (abbreviation), and subsequent uses should be the abbreviation. This consistency is lacking. For example, please review 'countermovement jumps (CMJ)' on page 6.
• Response: We thank the reviewer for pointing this out. We will carefully review the entire manuscript to ensure that all abbreviations are introduced in full at first use (e.g., “countermovement jump (CMJ)”, “center of mass (CoM)”, “wearable resistance (WR)”) and used consistently thereafter.

Reviewer 3 Report

Comments and Suggestions for Authors

This study investigates the application of wearable resistance (WR) training in specific jump interventions for female volleyball. The topic holds theoretical value; however, the manuscript still has significant shortcomings in research logic and methodological rigor, with the following specific comments:

1. Participants: Sixteen competitive female volleyball players were initially recruited, but in Section 2.2 only 13 participants are reported to have completed the study. Please unify the description throughout the manuscript.
2. The manuscript repeatedly uses abbreviations such as countermovement jump (CMJ) and center of mass (CoM) It is recommended to unify the abbreviation format and provide the full term with abbreviation only at the first occurrence, in order to improve the clarity and consistency of the writing.
3. In the Testing Procedures section, the pre-test involved 8 attempts, while the post-test included only 5 attempts. The process of familiarization with the testing environment should be carried out during the warm-up or in a separate familiarization session, rather than being incorporated into the formal test. The number of formal test trials should be consistent between pre- and post-tests. Furthermore, given the 10-week interval between tests, a familiarization arrangement is also necessary before the post-test to ensure comparability of results.
4. The inconsistency in the number of jump attempts between pre- and post-tests, combined with the fact that all attempts were performed with maximal effort, may have introduced cumulative fatigue effects, thereby affecting the stability and validity of the test results. It is recommended to include a separate familiarization session before the formal test and ensure the same number of attempts in both pre- and post-tests, in order to reduce the influence of fatigue and learning effects.
5. The kinematic analysis was based only on the single best jump from the pre- and post-tests. Using “the best single attempt” may be influenced by outlier performances, which increases variability and reduces reliability (e.g., ICC). In addition, inconsistency in the selection criteria between pre- and post-tests further undermines the accurate detection of effects. It is recommended to use “the average of the best multiple trials” or a pre-defined standardized selection method to improve the reliability and comparability of the data. Please justify whether selecting only one trial is sufficient to represent participants’ movement strategy.
6. 2.5 Measurements: “Beginning of countermovement jump (CMJ) was defined by the point at which center of mass (CoM) moved below zero-reference point” — this phrasing is imprecise and may lead to ambiguity. Please clarify the definition more rigorously.
7. 2.5 Measurements: the IR mat is mentioned, but the study primarily relies on the Xsens MVN Link system for kinematic measurements. If the IR mat was not a central measurement tool, it may be briefly mentioned without overemphasizing its importance.
8. 2.7 Statistics: multiple paired t-tests and independent t-tests were conducted, but it was not stated whether assumptions of normality were tested. Please clarify this point.
9. 3.3 Kinematic Analysis: although no significant differences between left and right legs were found, the manuscript exclusively analyzed the right side without discussing leg dominance. Why was the right leg chosen? Please justify this decision and consider potential dominance effects.
10. 3.4 Figures and Data Presentation (Sections 3.1–3.3): Several figures lack clear indications of statistical significance, and the correspondence between text descriptions and graphical presentations is insufficient. For example, Figures 4–5 (jump performance), Figures 6–7 (jump phase velocities, time, and depth), and Figures 8–9 (kinematic analysis) do not consistently highlight significant effects. It is recommended that the authors explicitly mark significant differences in the figures and ensure stronger alignment between graphical outputs and the textual explanations to improve clarity and interpretability.
11. 4.2 Discussion: For non-significant results (e.g., joint angles and angular velocities), the authors primarily attributed the lack of effects to measurement error, which is an overly simplistic explanation. Additionally, although the study reports a ~9.5% improvement in jump height, the discussion does not extend to the practical implications for volleyball-specific skills such as spiking and blocking. It is recommended that the authors provide more comprehensive interpretations of the non-significant findings and integrate the results with sport-specific performance outcomes to enhance the practical relevance of the discussion.
12. The performance indicators in this study overlap with kinematic indicators. Strictly speaking, jump height itself is a kinematic parameter, and it is recommended to reorganize the expression.

Author Response

We want to thank the reviewer for the comments. We have answered to all the comments the reviewer raised and think that the manuscript now is suitable for publication. Changes in the manuscript are collored in red.

This study investigates the application of wearable resistance (WR) training in specific jump interventions for female volleyball. The topic holds theoretical value; however, the manuscript still has significant shortcomings in research logic and methodological rigor, with the following specific comments:

1. Participants: Sixteen competitive female volleyball players were initially recruited, but in Section 2.2 only 13 participants are reported to have completed the study. Please unify the description throughout the manuscript.

• Response: We thank the reviewer for noticing this. The manuscript already states that 16 players were recruited and that 3 dropped out during the intervention, leaving 13 in the final analysis. To avoid any possible confusion, we will revise the opening sentence of the Participants section so that the full flow is clear right from the start.

2. The manuscript repeatedly uses abbreviations such as countermovement jump (CMJ) and center of mass (CoM) It is recommended to unify the abbreviation format and provide the full term with abbreviation only at the first occurrence, in order to improve the clarity and consistency of the writing.

• Response: We went through the entire manuscript to ensure that all abbreviations are introduced in full at their first appearance and then used consistently in abbreviated form thereafter.

3. In the Testing Procedures section, the pre-test involved 8 attempts, while the post-test included only 5 attempts. The process of familiarization with the testing environment should be carried out during the warm-up or in a separate familiarization session, rather than being incorporated into the formal test. The number of formal test trials should be consistent between pre- and post-tests. Furthermore, given the 10-week interval between tests, a familiarization arrangement is also necessary before the post-test to ensure comparability of results.

4.The inconsistency in the number of jump attempts between pre- and post-tests, combined with the fact that all attempts were performed with maximal effort, may have introduced cumulative fatigue effects, thereby affecting the stability and validity of the test results. It is recommended to include a separate familiarization session before the formal test and ensure the same number of attempts in both pre- and post-tests, in order to reduce the influence of fatigue and learning effects.

• We appreciate the reviewer’s observation. This was not an oversight but a deliberate design choice. As explained in Methods 2.3, the additional pre-test jumps were included to provide familiarization, since this was the players’ first exposure to the testing setup. From those 8 attempts, only the best 5 were retained for analysis, making the dataset directly comparable to the 5 post-test jumps. We agree that in future studies it would be preferable to provide a separate familiarization session and to keep the number of formal attempts identical across tests. To acknowledge this, we have added a note in the Limitations stating that the unequal number of attempts could have introduced minor fatigue or comparability effects. However, we believe this risk was minimal, as many athletes achieved their highest jump on the final attempt, which would not be expected if fatigue had significantly influenced performance.

5. The kinematic analysis was based only on the single best jump from the pre- and post-tests. Using “the best single attempt” may be influenced by outlier performances, which increases variability and reduces reliability (e.g., ICC). In addition, inconsistency in the selection criteria between pre- and post-tests further undermines the accurate detection of effects. It is recommended to use “the average of the best multiple trials” or a pre-defined standardized selection method to improve the reliability and comparability of the data. Please justify whether selecting only one trial is sufficient to represent participants’ movement strategy.

• Response: We see the reviewer’s point. Just to be clear, this wasn’t a decision made afterwards, in Methods 2.3 we already specified that we would analyze the best jump. The idea was to capture peak performance, which is often how maximal ability is tested in sport science (for example, best sprint, highest jump, or heaviest lift). We agree that averaging a few top jumps is also a solid approach. But research shows that it doesn’t really change the outcome, Petré et al. (2023) found CMJ results were equally reliable whether based on the best single jump or on the average of the top 2–3 jumps. So while our choice focused on peak effort, it wouldn’t have biased the results compared to an averaging method. That said, we can add a line in the Limitations to acknowledge that averaging top trials could help reduce variability and might be a useful strategy in future studies.

6. 2.5 Measurements: “Beginning of countermovement jump (CMJ) was defined by the point at which center of mass (CoM) moved below zero-reference point” — this phrasing is imprecise and may lead to ambiguity. Please clarify the definition more rigorously.

• Response: We agree that the original phrasing could be clearer. What we meant was that the start of the CMJ was identified as the moment when the CoM began to move downward from the upright standing position. To remove any ambiguity, we have revised the sentence in Methods 2.5.

7. 2.5 Measurements: the IR mat is mentioned, but the study primarily relies on the Xsens MVN Link system for kinematic measurements. If the IR mat was not a central measurement tool, it may be briefly mentioned without overemphasizing its importance.

• Response: We agree with the reviewer. The IR mat was used only to calculate jump height, while all kinematic analyses were based on the Xsens MVN Link system, which was the primary tool in this study. To make this clear, we added a short clarifying sentence in Methods 2.5.

 

8. 2.7 Statistics: multiple paired t-tests and independent t-tests were conducted, but it was not stated whether assumptions of normality were tested. Please clarify this point.

• Response: The assumption of normality for all ANOVAs and t-tests was tested using the Shapiro–Wilk test. No violations were detected, which supported the appropriateness of parametric analyses. We added this clarification in Methods 2.7 Statistics.

 

9. 3.3 Kinematic Analysis: although no significant differences between left and right legs were found, the manuscript exclusively analyzed the right side without discussing leg dominance. Why was the right leg chosen? Please justify this decision and consider potential dominance effects.

• Response: This is a fair point. In Results 3.3 we explained that no significant differences were found between the left and right side kinematics, and therefore only the right side was reported. We chose this approach to avoid repeating data that showed the same pattern on both sides. We did not formally test for leg dominance, which we agree could be relevant. To address this, we are happy to add a note in the Limitations section acknowledging that leg dominance was not assessed, and that future studies should consider this factor.

10. 3.4 Figures and Data Presentation (Sections 3.1–3.3): Several figures lack clear indications of statistical significance, and the correspondence between text descriptions and graphical presentations is insufficient. For example, Figures 4–5 (jump performance), Figures 6–7 (jump phase velocities, time, and depth), and Figures 8–9 (kinematic analysis) do not consistently highlight significant effects. It is recommended that the authors explicitly mark significant differences in the figures and ensure stronger alignment between graphical outputs and the textual explanations to improve clarity and interpretability.

• Response: We appreciate the reviewer’s comment. In our figures, significant differences are already indicated where appropriate. Other figures are intended to be descriptive, showing distributions and patterns even when no significant differences were detected. We chose this approach to provide readers with a full picture of the data rather than only presenting significant outcomes.

 

11. 4.2 Discussion: For non-significant results (e.g., joint angles and angular velocities), the authors primarily attributed the lack of effects to measurement error, which is an overly simplistic explanation. Additionally, although the study reports a ~9.5% improvement in jump height, the discussion does not extend to the practical implications for volleyball-specific skills such as spiking and blocking. It is recommended that the authors provide more comprehensive interpretations of the non-significant findings and integrate the results with sport-specific performance outcomes to enhance the practical relevance of the discussion.

• Response: We thank the reviewer for this point. To clarify, we did not intend to attribute the non-significant findings solely to measurement error. In the Discussion we also referred to the influence of small sample size and effect sizes, which we believe are equally important in explaining the lack of statistical significance. To address the reviewer’s concern, we will add a note linking the observed 9.5% increase in CMJ height to volleyball-specific skills such as spiking and blocking, as these are directly enhanced by even modest gains in jump height.

12. The performance indicators in this study overlap with kinematic indicators. Strictly speaking, jump height itself is a kinematic parameter, and it is recommended to reorganize the expression.

• Response: We thank the reviewer for pointing this out. While jump height is technically derived from kinematic data, in applied sports science it is widely reported as a performance measure, distinct from joint- and segment-level kinematics. To avoid confusion, we added a clarifying sentence in the manuscript to make this distinction explicit.

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The revised manuscript adequately addresses the reviewers’ comments and is acceptable for publication.

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Author Response

Thank you for reviewing the manuscript.

Reviewer 3 Report

Comments and Suggestions for Authors

The author responded comprehensively to the questions raised and revised the manuscript accordingly. The overall attitude was positive, and the revision direction was basically reasonable. However, it is suggested that relevant references should be introduced into the article's new or modified content to enhance the statement's scientific and persuasive content. Including but not limited to Training Intervention, Discussion, and other parts.

Author Response

We thank the reviewer for this suggestion. In the revised manuscript, we have added supporting references to strengthen the new or modified statements. Specifically, we included additional citations in the Training Intervention (performance relevance of CMJ gains), and Discussion (biomechanical explanations of discrepancies) sections. These references ensure that the arguments are better grounded in the existing literature. The included references are collored red in the text.