Comparative Biomechanical Strategies of Running Gait Among Healthy and Recently Injured Pediatric and Adult Runners

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

+ This is fine work, and I am curious as to whether this criteria has been researched in this format in the past. 

+ Excellent job outlining each of the methods, protocols, and instrumentation with justifying resources.

-- However, “Injured” is too vague to be of direct value here. The injury types would need to be categorized by type and perhaps stratified by severity to be meaningful. This is the primary concern with this work.

> Would like to see an outline of the practical, diagnostic, and/or therapeutic applications up front for context. 

> If possible, place the Abbreviations AND add a Glossary of terms at the beginning for reference before reading the manuscript, not after.

+ Selection and exclusion criteria were clear and helped with replicability. 

+ Statistics:  Good use of Kolmogorov-Smirnov; good application of ANCOVA as well. Descriptive statistics are sound and standard.

> Recommend using graphs for any compelling findings – those that are highly significant and worth highlighting.

+ Tables are set out nicely and easy to read - a couple formatting issues noted below. 

51, 52:  Is the higher variability in certain ranges or just more variable?
74-77:  You made the objectives fairly clear here.
93:  Figure captions should be placed under each figure - no need for one above as well. 
97:  What kind of gait services? Help the reader picture the nature of the lab setting. 
106:  Why exclude >35 years of age? They are also.' What distinguishes that age cutoff?
132-137:  A diagram for the markers is recommended here.
146:  Maybe missing "which' in front of 'was'?
147:  Why 8 minutes?
158:  Does this line need separating commas?
178: clarify what is meant by: "The pelvis was developed ..." Identified?
207-208:  'if' = 'whether'
235:  Is 'Adult' misaligned? - Should be moved to the right
234, 282, 325, 371:  Tables 1, 2, 3, 4 are excellent as noted above. Nicely organized.
237: Should be 'n=96'?
323: Left-justify ‘Adult’ in the column heading in Table 3

391: In the Discussion, subsections would be extremely helpful to divide the single large section into smaller meaningful subtopics. 

> The primary recommendation is to provide meaningful application and context for this work as mentioned at the beginning of the review – provide this at the end in greater detail. WHY was this undertaken? HOW can this information best be applied? Of what SIGNIFICANCE are the unsurprising findings?

 

 

Author Response

Comment 1: + This is fine work, and I am curious as to whether this criterion has been researched in this format in the past.

Response 1: Thank you for the kind words!  Specific biomechanical comparisons have been published previously in this format; several characterizations of kinematics and kinetics exist in particular age groups (citations 7, 8, 10, 11, 12, 14), and there are a few comparisons of biomechanical parameters between different age groups (citations 9, 13, 15, 16); however, to our knowledge, this study is the first attempt to quantify such differences for age AND injury status.

To highlight this novelty, we added the following statement in the last paragraph of the introduction (page 2, lines 78-80):

“While there are several attempts to characterize running biomechanics in different age populations with different injuries, there is no direct comparison of these features according to age and injury status.”

 

Comment 2: + Excellent job outlining each of the methods, protocols, and instrumentation with justifying resources.

-- However, “Injured” is too vague to be of direct value here. The injury types would need to be categorized by type and perhaps stratified by severity to be meaningful. This is the primary concern with this work.

Response 2: To clarify the meaning of “injured,” we specified injuries from our sample in section 2.4 of the methods (lines 132-135):

"Injury types present in this analysis included recent history of lower extremity stress fractures (healed and cleared to run), tendinopathies (Achilles, flexor hallicus longus, iliotibial band, extensor hallicus longus), plantar fasciitis, and hip labral pain or tear."

We appreciate the value of separating data into discrete diagnoses; however, our first analytic approach was hindered by the large number of injury types in the sample, which exceeded our statistical capacity. As such, we used the general approach as others have done to start with “injured” versus “not injured” first to determine the differences in this broad differentiation. We intend to look further into diagnoses that have greater cell numbers from which to explore this very question. The severity of pain – if present – was mild to moderate (1-6 on a 10-point numerical pain rating scale). We did not test people who ran with a limp or changed their form significantly due to pain, as this was not informative.

 

 

Comment 3: > Would like to see an outline of the practical, diagnostic, and/or therapeutic applications up front for context.

Response 3: Thank you for the suggestion. We added a section in paragraph 1 of the introduction (page 2, lines 44-50):

“Pediatric patients are not ‘small adults’ and are likely to have different running responses after an injury. A strong understanding of age-related mechanics is essential for clinicians and therapists to guide the return-to-run process after injury, enabling them to: 1) inform age-specific clinical approaches to gait retraining by tailoring loading rate reduction strategies and movement cueing techniques for younger versus older athletes, and 2) refine the goals and content of rehabilitation programs in distance runners with different injuries by age.”

We added to the last paragraph (Page 2, lines 78-81) before the aims: “While previous works have characterized running biomechanics in different age populations with different injuries, there is no direct comparison of these features according to age and injury status. As such, clinicians often extrapolate data from injured adults to develop interventions and cues for gait retraining in children and adolescents.”

 

Comment 4: > If possible, place the Abbreviations AND add a Glossary of terms at the beginning for reference before reading the manuscript, not after.

Response 4: We agree that making the abbreviations and glossary of terms easy to find is critical for the reader.  Based on journal formatting, however, the glossary is located at the end of the paper in the template. We defer to the editors if we are mistaken about this.

 

Comment 5: + Selection and exclusion criteria were clear and helped with replicability.

+ Statistics:  Good use of Kolmogorov-Smirnov; good application of ANCOVA as well. Descriptive statistics are sound and standard.

> Recommend using graphs for any compelling findings – those that are highly significant and worth highlighting.

Response 5: Thank you for this recommendation. We have added plots with the maximal joint moments in the sagittal and frontal planes across group and condition, and included them in the new Figure 3.

 

Comment 6: + Tables are set out nicely and easy to read - a couple formatting issues noted below.

51, 52:  Is the higher variability in certain ranges or just more variable?

Response 6:  The mean values for joint excursions are not reported in Pre-pubertal runners demonstrate greater variability in running kinematics than post-pubertal runners, https://doi.org/10.1016/j.gaitpost.2023.05.021. Thus, we are unable to conclude whether the variability was limited to specific ranges (joint angles) or if it was more generally variable.

 

Comment 7: 74-77:  You made the objectives fairly clear here.

93:  Figure captions should be placed under each figure - no need for one above as well.

Response 7: Thank you for bringing this to our attention.  The top caption was removed from Figure 1 on page 3.

 

Comment 8: 97:  What kind of gait services? Help the reader picture the nature of the lab setting.

Response 8: We agree that “gait services” can be more specific.  To provide more detail, we changed (page 3 lines 105-111):

“The Exercise Medicine and Functional Fitness laboratory is located within a quaternary health care facility and provides gait services to runners of all ages and experience levels. “

To: The Exercise Medicine and Functional Fitness Laboratory is located within a quaternary health care facility and provides gait services among several performance-based and injury prevention options. After physician referral or self-referral into the laboratory, the team offers 3D running motion analysis, functional movement assessment screen to identify kinetic chain deficits, training program recommendations, gait retraining with cueing, counseling on return-to-run programs, shoe wear selection, and therapeutic exercise to runners of all ages and experience levels (amateur to professional athletes).

 

Comment 9: 106:  Why exclude >35 years of age? They are also.' What distinguishes that age cutoff?

Response 9: Thank you for your question.  Our previous work shows that runners over age 35 represent distinct groups in terms of kinetic and kinematic characteristics: Reference biomechanical parameters and natural asymmetry among runners across the age spectrum without a history of running-related injuries (https://doi.org/10.3389/fspor.2025.1560756).  Thus, we excluded runners aged 35+ to eliminate distinct changes that occur with those aging brackets, given the pediatric focus of the current paper.

 

Comment 10: 132-137:  A diagram for the markers is recommended here.

Response 10: Thank you for the suggestion. A diagram is placed in the methods section under the marker description as the new Figure 2.

 

Comment 11: 146:  Maybe missing "which' in front of 'was'?

Response 11: Thank you for bringing this omission to our attention.  We have tried to improve readability and changed (page 5, lines 191-192): “Runners ran at a self-selected velocity was defined as the typical pace used for long distance run training.”

To: "Runners ran at a self-selected velocity, defined as the typical pace used for long-distance running."

 

Comment 12: 147:  Why 8 minutes?

Response 12: Thank you for that question.  We allocate 8 minutes to standardize our data collection process, allowing ample time for runners to achieve dynamic stability before data capture.  A couple of studies have shown that the first few minutes of running on a treadmill may not reflect steady-state biomechanics (https://doi.org/10.1080/14763141.2021.1873411; doi.org/10.3389/fspor.2025.1387934). Runners can produce variable gait signatures when transitioning into running on a novel surface, but that variability is reduced after allowing an acclimation period to adopt their “natural” gait. 

To address your question, we’ve added “After acclimating to the treadmill for eight minutes to ensure dynamic stabilization of kinematics,…” to line 193 on page 5

 

Comment 13: 158:  Does this line need separating commas?

Response 13: Yes- a separating comma was added on page 4, line 206.

Changed: “Several standard spatiotemporal spatial and kinematic variables were determined. Bone models were developed for each runner to establish individual center of mass (COM) ”

To: “Several standard spatiotemporal, spatial, and kinematic variables were determined. Bone models were developed for each runner to establish the individual center of mass (COM)…”

 

Comment 14: 178: clarify what is meant by: "The pelvis was developed ..." Identified?

Response 14: Thank you for bringing this to our attention. We are recounting the specific points on the participant that are used for the skeleton’s digital model. We can clarify what is meant by the pelvis being developed and changed: "The pelvis was developed from the anterior and posterior superior iliac spine markers, and the anterior inclination was expressed relative to the horizontal as 0° of anterior tilt."

 

Comment 15: 207-208:  'if' = 'whether'

Response 15: Thank you for your feedback.  We changed: “… anthropometric and training history continuous variables to determine if differences existed between age brackets.”

To: "… anthropometric, and training history continuous variables to determine whether differences existed between age brackets."

 

Comment 16: 235:  Is 'Adult' misaligned? - Should be moved to the right

Response 16: Thank you for addressing this misalignment.  The alignment for the column headings in Table 1 on page 7, line 285, has been adjusted.

 

Comment 17: 234, 282, 325, 371:  Tables 1, 2, 3, 4 are excellent as noted above. Nicely organized.

237: Should be 'n=96'?

Response 17: Yes, thank you for catching that. We have changed “n-96” to “n=96” on page 7, line 287, page 8, line 334, and page 9, line 368.

 

Comment 18: 323: Left-justify ‘Adult’ in the column heading in Table 3

Response 18: Thank you again.  “Adult” was left-justified in the column heading in Table 3 on Page 8, line 365.

 

Comment 19: 391: In the Discussion, subsections would be extremely helpful to divide the single large section into smaller meaningful subtopics.

Response 19: Thank you for that suggestion. We agree that subheadings would help. In the template format, however, the discussion section does not include subheadings. We will put them in as requested, but we will defer to the editor and remove them if advised. 

Two headers were created: “4.1 Age-Related Running Differences” on page 11, line 433, and “4.2 Injury-Related Running Differences” subsection on page 12, line 458.

 

Comment 20: > The primary recommendation is to provide meaningful application and context for this work as mentioned at the beginning of the review – provide this at the end in greater detail. WHY was this undertaken? HOW can this information best be applied? Of what SIGNIFICANCE are the unsurprising findings?

Response 20: Thank you for your perspective. We have addressed this issue more thoroughly in subsection 4.1. The following statement was added to the end of the section concerning pediatric runners (page 12, lines 454-456):

“Thus, emphasis should be on strengthening exercise and neuromotor activity in the core and lower extremities to improve kinematic stability.”

We also added the paragraph in the discussion (page 12, lines 472-480):

“Although adult runners are reported to learn to intuitively adopt compensatory running patterns when injured, it is clinically important to observe whether this adaptation is beneficial, or if it might worsen the injury or cause a new one. Blyton et al. found that the compensatory running gait persisted after the injury had healed in some athlete populations [##]. Clinicians and therapists need to understand maladaptive gait patterns. Identifying which age groups could benefit from interventions to correct maladaptive running gait before it becomes habitual may provide valuable information for the running community.”

In the “Injury-Related Running Differences” subsection, we address applications of our findings on lines 463-472; however, the following statement was added to emphasize provider awareness (page 13, lines 502 and 503):

“These findings can be directly implemented into clinical settings as part of tailored therapeutic programs for running athletes.”

Reviewer 2 Report

Comments and Suggestions for Authors

The MS by Verble and colleagues named “Comparative Biomechanical Strategies of Running Gait Among Healthy and Recently Injured Pediatric and Adult Runners” is aimed to highlight the differences in the running gait due to age and to study the effect of recent injury on biomechanical parameters of running patterns.

 

The study included 207 participants: 119 pediatric ( age less than 18 y., with n = 23 non-injured, or 19%), and 88 adult runners (age 25-35 y., with n = 13 non-injured, or 15%). Of the 13 non-injured adult runners 76.9% were female, - that makes 10 female and 3 male participants.

 

I wonder whether such number of non-injured adults was enough to provide a reference group and could the authors be sure that gender bias doesn’t affect the results as it is known that there are sex-specific differences in biomechanics among runners.

The other limitations of the study are clearly stated in the corresponding section.

 

The methodology of the research is well described and full details are provided in the Results section. A number of temporal spatial parameters of gait were measured, including cadence (step/min), COM displacements, step and stride length, stance and swing times. The authors had also measured ground reaction force (GRF), vertical average loading rate (VALR), ankle, knee, hip maximal joint moments in two planes.

 

Comparing the sets of parameters the authors conclude that the pediatric and adult runners exhibit distinct gait strategies. However these strategies were found to be independent of the injury status. This finding points out the probable need of different strategies for rehabilitation of pediatric runners compared to the adult ones.

 

Minor points:

lines 161-162. “Marker data were filtered at 9 Hz with a fourth-order, low-pass Butterworth filter” It is not quite clear why 9Hz and fourth-order were selected. May be add a reference or some explanation.

Table 1. “Adult” should be shifted right by 1 column.

Tables 1-3. “Injured n = 96” : misprint.

 

 

Author Response

Comment 1: The MS by Verble and colleagues named “Comparative Biomechanical Strategies of Running Gait Among Healthy and Recently Injured Pediatric and Adult Runners” is aimed to highlight the differences in the running gait due to age and to study the effect of recent injury on biomechanical parameters of running patterns.

The study included 207 participants: 119 pediatric ( age less than 18 y., with n = 23 non-injured, or 19%), and 88 adult runners (age 25-35 y., with n = 13 non-injured, or 15%). Of the 13 non-injured adult runners 76.9% were female, - that makes 10 female and 3 male participants.

I wonder whether such number of non-injured adults was enough to provide a reference group and could the authors be sure that gender bias doesn’t affect the results as it is known that there are sex-specific differences in biomechanics among runners.

The other limitations of the study are clearly stated in the corresponding section.

Response 1: Thank you for your comment. You make an interesting and fair point. We had not considered this, but we agree that there could be gender bias in the adult non-injured group, and it is essential to include this in the limitations section. We have added the following statement to the “Limitations and Future Directions” subsection on page 13, lines 522-527:

 “Finally, our sample size for adult non-injured runners (n=13) was relatively small, and there was a greater gender bias (Females = 76.9%), with the other three groups having a more equal distribution.  Given these characteristics of our convenience sample, we are unable to rule out the effect of gender on certain biomechanical parameters between these groups.  Future efforts should  aim for equal gender distribution to rule out sex-specific differences.”

 

Comment 2: The methodology of the research is well described and full details are provided in the Results section. A number of temporal spatial parameters of gait were measured, including cadence (step/min), COM displacements, step and stride length, stance and swing times. The authors had also measured ground reaction force (GRF), vertical average loading rate (VALR), ankle, knee, hip maximal joint moments in two planes.

Comparing the sets of parameters the authors conclude that the pediatric and adult runners exhibit distinct gait strategies. However these strategies were found to be independent of the injury status. This finding points out the probable need of different strategies for rehabilitation of pediatric runners compared to the adult ones.

 Response 2: Thank you for addressing this. The distinction between adult and pediatric gait is often overlooked. We agree that rehabilitation strategies should vary based on the data in each group.  We address this distinction in the discussion and offer recommendations for intervention targets in pediatric runners on page 12, lines 463-474: “Thus, emphasis should be on strengthening exercise and neuromotor activity in the core and lower extremities to improve kinematic stability.”

 

Minor points:

Comment 3: lines 161-162. “Marker data were filtered at 9 Hz with a fourth-order, low-pass Butterworth filter” It is not quite clear why 9Hz and fourth-order were selected. May be add a reference or some explanation.

Response 3: Thank you, we agree it’s not quite clear. To allow continuity in comparisons across studies, we’ve conformed to the convention established in gait and running analysis, recommending cutoff frequencies in the 6–12 Hz range based on residual analysis and signal-to-noise optimization. A 9 Hz cutoff is a well-balanced choice, effectively capturing running biomechanics while minimizing soft tissue artifacts. The fundamental frequencies of joint movements (hip, knee, ankle) and segment movements (thigh, shank, foot) during running typically fall below 9–12 Hz (https://pubmed.ncbi.nlm.nih.gov/31438944/). A fourth-order implementation offers a steeper roll-off, effectively removing high-frequency noise without excessively affecting lower-frequency components.

Here are a few papers in this area that discuss these issues:

https://www.mdpi.com/1424-8220/21/13/4580; https://pmc.ncbi.nlm.nih.gov/articles/PMC3916920/; https://ascelibrary.org/doi/10.1061/%28ASCE%290733-9453%282004%29130%3A4%28175%29

We have added additional clarification in section 2.5 on page 5, lines 211-214: “Studies in gait and running analysis recommend cutoff frequencies in the 6–12 Hz range based on residual analysis and signal-to-noise optimization. A 9 Hz cutoff is a well-balanced choice, effectively capturing running biomechanics while minimizing soft tissue artifacts.”

 

Comment 4: Table 1. “Adult” should be shifted right by 1 column.

Response 4: Thank you for addressing this misalignment.  The alignment for the column headings in Table 1 on page 7, line 285, has been adjusted.

 

Comment 5: Tables 1-3. “Injured n = 96” : misprint.

Response 5: Yes, thank you for catching that. We have changed “n-96” to “n=96” on page 7, line 287, page 8, line 334, and page 9, line 368.

Reviewer 3 Report

Comments and Suggestions for Authors

This manuscript systematically investigates the biomechanical strategies employed during running by healthy and recently injured pediatric and adult individuals. While the topic carries certain scientific relevance, the manuscript has significant deficiencies in terms of theoretical innovation, data processing, and presentation. In my opinion, it is not suitable for publication in its current form.

 

1.The study explores the effects of age and physical condition on running gait, which is of practical importance. However, the manuscript fails to clearly specify which types of injuries or running speeds are being investigated. Moreover, similar studies can already be found in the literature, and the authors have not articulated any specific original contributions that distinguish this work from prior research.

 

2.In terms of data presentation, the manuscript includes only one figure—a process flow diagram—which conveys no actual data. The tables provided also fail to clearly emphasize or explain the study’s key findings.

 

3.The experimental setup raises major concerns. It is well known that different running speeds require different postures and ground reaction forces, and these should be clearly recorded and statistically analyzed. Likewise, the effects of different types of injuries on running mechanics should be documented in detail. As for age grouping, the exclusion of individuals aged 19–24 is arbitrary and unexplained. Although running speed and sex were included as covariates in the analysis, other critical variables—such as years of training, type of rehabilitation intervention, presence of pain, foot strike pattern, and footwear characteristics—were not stratified or regressed. These factors are known to significantly affect gait (as the authors themselves note that the adult runners had an average of 5 years’ running experience), raising substantial concerns about the internal validity of the results.

 

4.Each participant’s gait was sampled for only 10 seconds, yielding approximately 12–14 gait cycles. This extremely limited sampling duration is insufficient to capture the natural variability of running, particularly for a key outcome like “gait timing variability,” making the evaluation of this parameter highly unreliable.

 

5.Although the conclusion recommends “age-specific rehabilitation strategies,” the manuscript provides neither a concrete training framework nor any rehabilitation guidelines. The study fails to transition from observational findings to a meaningful intervention design, and thus lacks clinical or practical relevance. It is already widely understood that individuals of different ages and health conditions display distinct movement characteristics. The true value of this work should lie in clearly identifying these differences and proposing actionable strategies to leverage them—yet the manuscript offers no such synthesis or applied insight.

Author Response

Comment 1: This manuscript systematically investigates the biomechanical strategies employed during running by healthy and recently injured pediatric and adult individuals. While the topic carries certain scientific relevance, the manuscript has significant deficiencies in terms of theoretical innovation, data processing, and presentation. In my opinion, it is not suitable for publication in its current form.

 1.The study explores the effects of age and physical condition on running gait, which is of practical importance. However, the manuscript fails to clearly specify which types of injuries or running speeds are being investigated. Moreover, similar studies can already be found in the literature, and the authors have not articulated any specific original contributions that distinguish this work from prior research.

Response 1: We appreciate the feedback and agree we should refine our message. To highlight the distinction, a statement was added in our introduction (page 2, lines 78-81):

“While previous works have characterized running biomechanics in different age populations with different injuries, there is no direct comparison of these features according to age and injury status. As such, clinicians often extrapolate data from injured adults to develop interventions and cues for gait retraining in children and adolescents.”

Further clarification of injury types present in this analysis has also been added to the Methods section on page 4 (lines 131-134):

“Injury types present in this analysis included recent history of lower extremity stress fractures (healed and cleared to run), tendinopathies (Achilles, flexor hallicus longus, iliotibial band, extensor hallicus longus), plantar fasciitis, and hip labral pain or tear.”

Running speed was variable, and to minimize kinematic and kinetic variability within a test, runners chose a comfortable pace, increasing the similarity to habitual running. We have described the process on page 5, line 192: “Runners ran at a self-selected velocity, defined as the typical pace used for long-distance running.” The mean and standard deviations for running speed as a function of subgroup are shown in Table 2 and are shown to be significantly different by age.

 

Comment 2: In terms of data presentation, the manuscript includes only one figure—a process flow diagram—which conveys no actual data. The tables provided also fail to clearly emphasize or explain the study’s key findings.

Response 2: Thank you for this recommendation. We have added Figure 2 on page 5 to depict the marker location for 3D motion analysis. We have also added plots with the maximal joint moments in the sagittal and frontal planes across group and condition, and included them in the new Figure 3 on page 10.

 

Comment 3: The experimental setup raises major concerns. It is well known that different running speeds require different postures and ground reaction forces, and these should be clearly recorded and statistically analyzed. Likewise, the effects of different types of injuries on running mechanics should be documented in detail. As for age grouping, the exclusion of individuals aged 19–24 is arbitrary and unexplained. Although running speed and sex were included as covariates in the analysis, other critical variables—such as years of training, type of rehabilitation intervention, presence of pain, foot strike pattern, and footwear characteristics—were not stratified or regressed. These factors are known to significantly affect gait (as the authors themselves note that the adult runners had an average of 5 years’ running experience), raising substantial concerns about the internal validity of the results.

Response 3: We understand these challenges to running science, and we agree that different speeds relate to different kinetics and kinematics, but this relationship is not clearly defined, nor is it considered causal. Variable mechanics are inherent to running, especially across individuals, even at constant speeds. This work provides insight into a more comprehensive characterization of these metrics as they relate to speed.

Requiring runners to use a standardized speed or standardized footwear relates to changes in biomechanics, metabolic energetics, and increasing variability in these metrics. The use of habitual shoes during the lab testing is also standard practice for running clinics (with whom we were partnered). Moreover, choosing people with only one foot strike type and or a specific number of years of training limits the generalizability of the findings. It enables conclusions for only small subsets of runners. These have been important variables that have been controlled in previous studies of adult runners when studying discrete questions, and it was not our intent to study these questions here.

From a clinical perspective, runners seeking care are like those presented here – a diverse mix of experience levels, shoe wear types, foot strikes, and preferred running speeds. From the findings that we see in this study, we ask: what are the apparent differences that manifest even with these variations? How can these differences be used to guide the therapy foci? How can we use these findings to support better gait retraining cues for pediatric and adult runners? We were able to achieve this. The different types of injuries sustained by the affected runners varied (as would be expected within a clinic-referred service in this lab). Separating every single injury type and severity for separate analysis by age is not reasonable due to minuscule sample sizes that are no longer able to be analyzed. The resources, timing, and sample number needed to achieve this goal have prohibited any one investigator group from being able to do this. However, we indicate here that even with these expected variations in the runners who were enrolled, we were still able to detect specific differences in pediatric and adult runners, which is the key starting point for any future analysis that focuses on the impact of select diagnoses on biomechanics.

 Please see below for some additional support about self-selected velocities:

Running Velocity: It is also common practice in running research to allow runners to choose their velocity, particularly if the group is diverse. While our previous data show that runners of different ages during experimental sessions can run across a variety of standardized speeds, it is not their realistic behavior, and they did not prefer it. This has metabolic efficiency implications and could contribute to spurious results.

               Sample publications that also use self-selected velocities are listed here:

https://pubmed.ncbi.nlm.nih.gov/39108456/, https://pubmed.ncbi.nlm.nih.gov/28666810/

https://pubmed.ncbi.nlm.nih.gov/38364508/ , https://pubmed.ncbi.nlm.nih.gov/35497357/,

https://pubmed.ncbi.nlm.nih.gov/38265344/

https://pubmed.ncbi.nlm.nih.gov/37116303/

https://pubmed.ncbi.nlm.nih.gov/29289028/

https://pubmed.ncbi.nlm.nih.gov/37249347/

 

Running velocity was used as a covariate in our analyses to account for any confounding effects, as has been published previously (https://pubmed.ncbi.nlm.nih.gov/33064822/) and in our prior publications (https://pubmed.ncbi.nlm.nih.gov/36454920/, https://pubmed.ncbi.nlm.nih.gov/38905854/).

 

For runners to test using their own shoes, several established running investigator groups used this approach:

https://pubmed.ncbi.nlm.nih.gov/33774324/

https://pubmed.ncbi.nlm.nih.gov/29975300/

https://pubmed.ncbi.nlm.nih.gov/30862272/

https://pubmed.ncbi.nlm.nih.gov/38364508/

https://pubmed.ncbi.nlm.nih.gov/36588173/

https://pubmed.ncbi.nlm.nih.gov/39771897/

Covariates. For the iterative analysis incorporating the covariate factors mentioned above, the faculty who ran the statistics included these variables in the ANCOVA models for the biomechanical outcomes (specifically, shoe characteristics, training years, and pain presence (yes/no)). These did not change the overall significance of the findings for these dependent variables. As such, the two key covariates (velocity, sex) were retained in the models for simplicity. Study groups with mixed foot strike have also been used previously to represent the general human running population best:

https://pubmed.ncbi.nlm.nih.gov/24746605/

https://pubmed.ncbi.nlm.nih.gov/26283411/

https://pubmed.ncbi.nlm.nih.gov/40251769/

 

Finally, the age group 19-24 was not arbitrary; instead, it provided a clear separation between pediatric and adult runners. For example, comparison of biomechanics using age as the independent variable would be meaningless if, in the big picture, we compared a 17.9-year-old to an 18.2-year-old, who are technically pediatric and adult individuals. To ensure a clear, distinct separation between pediatric and adult runners, the study team decided to separate the inclusion into the groups by 5 years.

 

Comment 4: Each participant’s gait was sampled for only 10 seconds, yielding approximately 12–14 gait cycles. This extremely limited sampling duration is insufficient to capture the natural variability of running, particularly for a key outcome like “gait timing variability,” making the evaluation of this parameter highly unreliable.

Response 4: Thank you for your comment. This is the standard practice among running studies to capture this number of cycles, and we disagree that it is unreliable. Typically, gait dynamic stability occurs after a few minutes of running on a treadmill, and we collected these data after 9 minutes of running. Many published studies, unfortunately, do not even describe the actual number of cycles, strides, or steps collected – so many more studies likely exist with this sampling that we used here.

Here are examples of published studies that captured this range of gait cycles in the running literature (these are but a few with instrumented treadmills):

https://pubmed.ncbi.nlm.nih.gov/29614001/

https://pubmed.ncbi.nlm.nih.gov/29614463/

https://pubmed.ncbi.nlm.nih.gov/40251769/

https://pubmed.ncbi.nlm.nih.gov/24380685/

https://pubmed.ncbi.nlm.nih.gov/39771897/

 

 

Comment 5: Although the conclusion recommends “age-specific rehabilitation strategies,” the manuscript provides neither a concrete training framework nor any rehabilitation guidelines. The study fails to transition from observational findings to a meaningful intervention design and thus lacks clinical or practical relevance. It is already widely understood that individuals of different ages and health conditions display distinct movement characteristics. The true value of this work should lie in clearly identifying these differences and proposing actionable strategies to leverage them—yet the manuscript offers no such synthesis or applied insight.

Response 5: Thank you for your perspective. While we do make specific recommendations for tailoring interventions for populations, this study is not “a complete framework” – nor should it be at this stage, for it would be premature to do so. Here, we provide the necessary starting points in the discussion to provide focus for the subsequent studies with increasing specificity and exclusivity.  To develop such a framework, we require direct data to support specific interventions aimed at achieving a desired change, to reach consensus through our studies and those of others, and to implement a structured program that validates its utility. 

What is provided here are actionable steps for rapid implementation; for example, cueing “pre-activation of lower extremity muscles…” and increasing cadence in adults can alter kinetic and kinematic signatures. We have addressed this issue more thoroughly in subsection 4.1. The following statement was added to the end of the section concerning pediatric runners (page 12, lines 454-456):

“Thus, emphasis should be on strengthening exercise and neuromotor activity in the core and lower extremities to improve kinematic stability.”

In the “Injury-Related Running Differences” subsection, we address applications of our findings on lines 463-472; however, the following statement was added to emphasize provider awareness (page 12, lines 493 and 494):

“These findings can be directly implemented into clinical settings as part of tailored therapeutic programs for running athletes.”

We also added the paragraph in the discussion (page 12, lines 472-480)

Although adult runners are reported to learn to intuitively adopt compensatory running patterns when injured, it is clinically important to observe whether this adaptation is beneficial, or if it might worsen the injury or cause a new one. Blyton et al. found that the compensatory running gait persisted after the injury had healed in some athlete populations [##]. Clinicians and therapists need to understand maladaptive gait patterns. Identifying which age groups could benefit from interventions to correct maladaptive running gait before it becomes habitual may provide valuable information for the running community.

 

We currently have two other studies in motion that are implementing retraining practices and determining effectiveness by age and diagnoses. However, we propose that this is outside the scope of the current paper and should be included in a separate manuscript.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Thank you for graciously addressing the recommendations and answering all of the questions. Each of the major concerns has been addressed and clarified, and typos or formatting issues have been rectified.

The added figures and graphs are extremely helpful and elevate the quality of your presentation. The extra effort you invested to address these elements has raised the bar for this work.

Well done, and I wish you all the best with your work. 

Author Response

Thank you for your comments

Reviewer 2 Report

Comments and Suggestions for Authors

Thanks, I've got all the answers.

Author Response

Thank you for your comments

Reviewer 3 Report

Comments and Suggestions for Authors

The authors have addressed most of my concerns, but the following issues remain unanswered or unresolved:

1. In lines 20–21 of the Abstract, the authors state that “VALR (BW/s) were higher among injured groups, irrespective of age (p < 0.05).” However, Table 3 shows that the main effect of injury is not significant, and only an age main effect is present. Based on the reported p-values, this claim appears to be incorrect.

2. The authors still have not explained the sampling issue. The healthy adult group has only n = 13, whereas the injured minor group has n = 96. The age strata are discontinuous and exclude participants aged 19–24, which is precisely the critical transition period from adolescence to adulthood. The authors should explain why this cohort is missing.

3. The authors have not clearly addressed my previous third concern. The analyses include only “speed” and “sex” as covariates, yet the groups differ substantially in foot-strike pattern, shoe heel-to-toe drop, and exposure to strength training—none of which were included in the model—introducing considerable confounding bias. Foot-strike patterns and the initial contact location vary with running speed, and training history can markedly change performance. For example, the authors conclude that injured adults tend to adopt load-reduction strategies during stance, while injured minors emphasize temporal stability and pelvic control with insufficient “mechanical” modulation of impact. Is this solely attributable to age? Is it independent of running speed and training status?

Author Response

Needs to be improved: Does the introduction provide sufficient background and include all relevant references? Is the research design appropriate? Are the conclusions supported by the results?

The authors have addressed most of my concerns, but the following issues remain unanswered or unresolved:

Comment 1: In lines 20–21 of the Abstract, the authors state that “VALR (BW/s) were higher among injured groups, irrespective of age (p < 0.05).” However, Table 3 shows that the main effect of injury is not significant, and only an age main effect is present. Based on the reported p-values, this claim appears to be incorrect.

Response 1: Thank you for bringing this to our attention. You are correct; this was backwards. We have revised the abstract, and lines 20-21 now read: “VALRs (BW/s) were higher among pediatric groups, irrespective of injury (p<0.05).”

Comment 2: The authors still have not explained the sampling issue. The healthy adult group has only n = 13, whereas the injured minor group has n = 96. The age strata are discontinuous and exclude participants aged 19–24, which is precisely the critical transition period from adolescence to adulthood. The authors should explain why this cohort is missing.

Response 2: The issue of life transition is the precise point why we did not include this age group – we wanted an obvious distinction from adolescence and adulthood, and not an age bracket that was very close to the adolescent range. Given that there are documented age differences in metrics of healthy runners even between pre-pubescent and post-pubertal runners (Close et al, 2024; Schepens et al., 1998), we wanted to avoid any variability associated with the transitions from adolescence to adulthood. Moreover, some individuals may be 19 years of age and still in high school, whereas others may be in college or competing at a very different level. We have added a sentence for this in the text under Section 2.3 “Participants” (pg 4, lines 122-125): “Exclusion of the ages 19-24 was to ensure that we assessed runners with stable mechanics who were in distinct age groups and not transitioning from adolescence to adulthood, and to avoid the systemic age changes in running form beyond the age of 35 years.”

 

Comment 3: The authors have not clearly addressed my previous third concern. The analyses include only “speed” and “sex” as covariates, yet the groups differ substantially in foot-strike pattern, shoe heel-to-toe drop, and exposure to strength training—none of which were included in the model—introducing considerable confounding bias. Foot-strike patterns and the initial contact location vary with running speed, and training history can markedly change performance. For example, the authors conclude that injured adults tend to adopt load-reduction strategies during stance, while injured minors emphasize temporal stability and pelvic control with insufficient “mechanical” modulation of impact. Is this solely attributable to age? Is it independent of running speed and training status?

 

Response 3: We provided a detailed response to the reviewers in our initial submission, which included running all ANCOVAS with all factors in the models (including foot-strike pattern, shoe heel-to-toe drop, and exposure to strength training). These analyses did not reveal any significant contributions to the models.

Regarding independence from speed and training status, none of the covariates (all listed above) showed significant multicollinearity with the independent variables of injury and age groups. All Variance Inflation Factors (VIF) were well below the problematic threshold of 5 (ranging from 0.329 to 3.173), supporting the validity of the effects of age and injury status as independent. Therefore, age and injury influence dependent variables independently of running speed, strength training status, shoe wear characteristics, foot strike pattern, and sex.

 

 

Author Response File: Author Response.docx