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Article
Peer-Review Record

Evaluating a New Optical Device for Velocity-Based Training: Validity and Reliability of the PowerTrackTM Sensor

by Fernando Martin-Rivera 1, Darío Rodrigo-Mallorca 1, Luis M. Franco-Grau 1, Jose Vidal-Vidal 2, Angel Saez-Berlanga 1,* and Iván Chulvi-Medrano 1
Reviewer 1: Anonymous
Reviewer 2: Anonymous
Submission received: 23 June 2025 / Revised: 31 July 2025 / Accepted: 7 August 2025 / Published: 11 August 2025

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This study evaluated the validity and reliability of the new optoelectronic device PowerTrackTM in measuring mean velocity (MV), mean propulsive velocity (MPV), and maximum velocity (Vmax) during Smith machine squats. My main concerns are as follows:

  1. The training level of the subject group (such as weekly training frequency, squat 1RM range, etc.) and its differences from the general fitness population were not explained.
  2. Although the PowerTrackTM was mentioned as a "new optoelectronic device", it was not introduced in detail, and the differences in its core technical parameters (such as sampling frequency, measurement range, optical sensor principle) from the criterion device (MuscleLabTM, 200Hz sampling rate) were not elaborated.
  3. The calculation method of the CV value (e.g., 13.20% for MV at 20kg) was not specified (such as intra-session or inter-session).
  4. The results showed that there was a proportional bias in MV (slope = 0.83), but the impact of this bias on actual training was not analyzed.
  5. The main text only mentioned the "systematic bias range (-0.01–0.07)" of the Bland-Altman plot, but did not analyze whether the bias changes with load/velocity (e.g., whether the bias is greater under light loads).
  6. The discussion section listed the limitations but did not propose specific improvement directions.

Author Response

Please see the attachment document.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This study assesses the validity and reliability of the PowerTrack optoelectronic device for measuring MV, MPV, and Vmax during Smith machine back squats, using MuscleLab as a reference. However, several aspects require improvement to enhance the clarity of the study.

  1. The authors should report the manufacturer-specified accuracy of both PowerTrack™ and MuscleLab™ (e.g., resolution, sampling rate), as this information is essential for evaluating device performance.
  2. Section 2 should include a structural diagram of the experimental setup to improve understanding of system configuration and flow. In Subsection 2.1, it is unclear whether rest periods were given between repetitions or loads. The authors should clarify this, specify the duration, and briefly discuss its potential impact on fatigue and measurement consistency

  3. The study only includes male participants. The authors should acknowledge this limitation and discuss its implications for generalizing results to other populations (e.g., females, untrained individuals).

  4. Figures have low resolution and small font sizes, making them difficult to read. The authors should enhance the figure quality for better clarity.

  5. The conclusion is too brief. It should be expanded to summarize the key findings, practical relevance, and suggest directions for future work.

With the above comments, I recommend accepting the manuscript after a minor revision. 

Author Response

Please see the attachment file

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Dear Authors,

thank you for sending the article titled: Evaluating a new optical device for velocity-based training: Validity and reliability of the PowerTrackTM sensor for review. IArricle seems interesting at first sight, but I suggest correct it as follows:

  • please include a flowchart of the experiment
  • Figure 1 - the quality should be improved - actually not readable. I suggest include subfigures as .svg
  • line 119 height parameter 1.72 (0.73) - I think that there is error in SD (bracket) - to high value of SD, Coefficient of variation almost 42.44%
  • Authors wrote: Inertial measurement units (IMUs), including the PUSH Band and Beast Sensor, offer enhanced portability; however, their validity tends to decline under high-speed or high-load conditions. I can't agree with this sentence, because IMU can obtain parameters with frequency 1000Hz. For example in the article titled: Unveiling the Abusive Head Trauma and Shaken baby Syndrome: A Comprehensive Wavelet Analysis,  Biomedical Signal Processing and Control, 2025, 107, 107862 https://doi.org/10.1016/j.bspc.2025.107862authors used IMU for obtain kinematic parameters. Moreover by using IMU it can be possible to calculate force generated by muscles. To improve article quality I suggest cite above manuscript and write a few sentences in the Introduction section
  • subsection 3.1 please include p-value of regression lines

Author Response

Please see the attachment file

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have adequately addressed all of my concerns. I recommend the manuscript for acceptance.

Author Response

Reviewer Comment: "The authors have adequately addressed all of my concerns. I recommend the manuscript for acceptance."

Response: "We sincerely thank the reviewer for the careful evaluation of our manuscript and for acknowledging the improvements made. We greatly appreciate your constructive feedback throughout the revision process, which has significantly contributed to enhancing the scientific rigor and clarity of our work.

Thank you once again for your recommendation and support."

Reviewer 3 Report

Comments and Suggestions for Authors

Thank you for the thoughtful and well-reasoned response. I understand and appreciate the authors’ explanation regarding the biomechanical and contextual differences between their study and the example I cited. That said, my intention was not to equate the movement patterns or experimental conditions, but rather to highlight the technical capabilities of modern IMUs—particularly their ability to capture high-frequency kinematic data, even in demanding scenarios. I believe that briefly acknowledging this in the introduction (e.g., a sentence such as “Recent research has also demonstrated the potential of high-frequency IMUs in complex dynamic tasks”) would help position the PowerTrack sensor in the broader context of motion analysis technologies. Therefore, I would kindly encourage the authors to reconsider incorporating the suggested reference—not to shift the focus of the paper, but simply to provide readers with a broader perspective on the evolving landscape of wearable sensors used in biomechanics and performance monitoring.

Author Response

Reviewer Comment: "Thank you for the thoughtful and well-reasoned response. I understand and appreciate the authors’ explanation regarding the biomechanical and contextual differences between their study and the example I cited. That said, my intention was not to equate the movement patterns or experimental conditions, but rather to highlight the technical capabilities of modern IMUs—particularly their ability to capture high-frequency kinematic data, even in demanding scenarios. I believe that briefly acknowledging this in the introduction (e.g., a sentence such as “Recent research has also demonstrated the potential of high-frequency IMUs in complex dynamic tasks”) would help position the PowerTrack sensor in the broader context of motion analysis technologies. Therefore, I would kindly encourage the authors to reconsider incorporating the suggested reference—not to shift the focus of the paper, but simply to provide readers with a broader perspective on the evolving landscape of wearable sensors used in biomechanics and performance monitoring."

Response: "We sincerely appreciate the reviewer’s thoughtful clarification and acknowledge the value of highlighting the broader technical capabilities of inertial measurement units (IMUs), particularly their high-frequency data acquisition in complex dynamic contexts. In response to this insightful suggestion, we have incorporated a brief statement in the Introduction to acknowledge this perspective: “Recent research has also demonstrated the potential of high-frequency IMUs in complex dynamic tasks, further enriching the landscape of motion analysis technologies.” However, we also emphasize that, due to the linear and controlled nature of barbell trajectories in our experimental setting (Smith machine back squat), the specific biomechanical demands of our study may limit the applicability of IMUs in this context. Nonetheless, the inclusion of this statement ensures that the PowerTrack™ system is appropriately situated within the broader framework of contemporary motion analysis tools. Thank you for encouraging us to expand the contextual scope of our manuscript."

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