Effect of Sex-Specific Running Shoes on Female Recreational Runners
and Tyler Standifird
Helen Branthwaite
Round 1
Reviewer 1 Report
The main aim of the paper „Effect of Sex-Specific Running Shoes on Female Recreational Runners“ was to determine if there are biomechanical, physiological, or perceived comfort differences present in female runners while running in sex-specific running shoes compared to non-sex-specific running shoes. The authors hypothesized that there will be no significant difference between the male and female shoe regarding GRFs, sagittal plane joint angles and moments as well as VO2, RER, or perceived level of comfort.
The study is interesting. I would like to appretiate the efforts of the authors. However, some facts need to be explained:
The order of references is alphabetical, not according to the order of reference in the text.
How many pairs of shoes were available for the research? All the shoes were of the same type as regards the method of treading?
Are the design differences between the male and female versions of used shoes known?
How exactly were the tests randomized?
What was the running speed used? Was it the same for all participants? How was this speed determined?
Although the individual curves are described in the title of the graphs, for clarity it would be advisable to include them in the label directly in the graph.
In table 2 is there really SD=4.78 for male shoe at VO2 value?
Author Response
General Response:
First and foremost, we would like to sincerely thank the reviewer for taking the time to thoroughly review our manuscript and offer feedback on areas where we can improve. We thank the Editor-in-Chief for the opportunity to re-submit the manuscript as well. Attached you will find the revised manuscript entitled: “Effect of Sex-Specific Running Shoes on Female Recreational Runners” that we hope you find acceptable for publication in the Journal of Applied Sciences. Updates to the manuscript have been highlighted in the revised version.
The order of references is alphabetical, not according to the order of reference in the text.
Response: The order of references has now been changed to the order referenced in the text.
How many pairs of shoes were available for the research? All the shoes were of the same type as regards the method of treading?
Response: We have edited the methods to now include information regarding shoe characteristics. LL 93-108 now states:
“Ten pairs of shoes were utilized in this research project. The male shoe sizes ranged from 7.0-9.5 US (40-43 Europe) and the female shoe size ranges were from 8.5-11 US (39-42 Europe). We ensured that each female shoe size had a corresponding male shoe size in order to make accurate comparisons. From industry standard sizing charts, the corresponding female shoe to the male shoe is identical in shape and size. Tread patterns were identical between the two shoes. Regarding design differences, the Altra female shoe is marketed as being specifically designed for women with their trademarked “FIT4HER” technology. According to Altra, this technology specifically addresses the unique sex in the female foot as stated on their website [25]. The female shoe has a narrower heel, longer arch and an altered angle of the footpad under the metatarsal heads compared to the male shoe. In addition, the male and female shoe molds differ in that the male shoe width is built on a D width from heel through midfoot and a 2E toe box. The female shoe is built on a B width from heel through midfoot and with a D-E toe box. The insole (5mm) and stack height (28 mm) are completely identical for both shoes according to the Altra website. Lastly, the female shoe weighs 241 g and the male shoe weighs 286 g [25,26].
Are the design differences between the male and female versions of used shoes known?
Response: Please see the above response.
How exactly were the tests randomized?
Response: The tests utilized a counterbalanced randomization design. A clarification sentence was placed in the text: “A counterbalanced randomization method was used to randomize the shoe conditions. The selected condition was then placed on the participant along with reflective markers on the feet.” LL 108-110
What was the running speed used? Was it the same for all participants? How was this speed determined?
Response: The running speed varied between participants. Participants were asked to run at a speed that they normally run. A clarification sentence was placed in the methods section: “A self-selected running speed was determined for each participant based on the pace at which they were most comfortable running.” LL 115-117
Although the individual curves are described in the title of the graphs, for clarity it would be advisable to include them in the label directly in the graph.
Response: We thank the reviewer for advising the addition titles be added to the individual curves. We respectfully contend that countless studies referenced by the current study do not make use of individual graph titles and present data in the same graphical format as the original manuscript of this article (Richert et al. 2019; Johnson et al. 2020; Sinclair et al. 2015; Milner et al. 2006; Ferber et al. 2003). However, all individual curves now have titles for clarity if the reviewer strongly advises it.
In table 2 is there really SD=4.78 for male shoe at VO2 value?
Response: The SD for the female shoe was entered incorrectly and has now been changed to the correct value of 4.43. The SD for the male shoe is correctly presented in the table.
Reviewer 2 Report
A really interesting and bold study. The content and research question are valuable to the wider reading audience and the paper is unique in its simplicity. There are a number of typo and grammar errors throughout the manuscript that need to be addressed to ensure that the flow and read of the paper is worthy.
Specifically though:
The last line of the abstract adds nothing to the discussion or conclusion. I strongly suggest that it is removed.
Introduction:
Running shoe design has evolved rather than changed, there are not so many differences in designing the shoe. they all have a sole, a lacing mechanism etc..
The second paragraph looking at associating pathology to shoe design needs to be altered, I would suggest that the team look at making the association between biomechanical outcomes, pathology and shoe design much clearer as it stands this is currently confusing and inaccurate. For instance the heel to toe drop is nothing to do with the amount of cushioning under the heel and forefoot but is a measure of difference in height of the sole unit in these areas. There is also a weak association between pathology and shoe design, A recent paper indicates that those who have plantar heel pain wear stiffer soled shoes than those who don't. Landorf, K.B., Kaminski, M.R., Munteanu, S.E., Zammit, G.V. and Menz, H.B., 2022. Activity and footwear characteristics in people with and without plantar heel pain: A matched cross‐sectional observational study. Musculoskeletal Care.
If the team are looking to link the possible association between injury, outcome measures and shoe design it needs to be a suggestive way rather than so blunt and direct.
Line 64 - which running shoe company? Altra?
Methods:
Line 80 doesn't make sense
Indicate in the methods what the differences in the shoe were - Is there actually are any difference in key shoe features or are the two shoes tested just marketed at male and females ? Information to include could be based on the footwear assessment tool by Barton et al 2009 Barton, C.J., Bonanno, D. and Menz, H.B., 2009. Development and evaluation of a tool for the assessment of footwear characteristics. Journal of foot and ankle research, 2(1), pp.1-12.
Was the comfort scale just literally one question - do the shoes feel comfortable? If so, this is not how other studies have assessed comfort - Mundermans scale with a multi faceted approach is mostly used. Just a one dimension overall NRS is not a full view of the comfort of the shoe.
Results
Why was only right leg used?
Discussion
Lines 156 - 170 looking at heel stack and GRF - what was the heel stack on this shoe was there a difference between the two shoes - the team are not discussing the results here but repeating and extending the introduction. You haven't computed PFjt force, so why is it being discussed.
The main limitation of this manuscript is the lack of assessment and discussion about the two shoes tested. The reason for no difference between each condition could be that there are no differences between the shoes, they are purely marketed at women or men.
Expand this part of the manuscript to indicate what the differences were, even to exploit ultra in any claims they make between the two types of shoe. For instance the womens shoe is lighter by 40g, but are other features are the same.
Author Response
First and foremost, we would like to sincerely thank the reviewer for taking the time to thoroughly review our manuscript and offer feedback on areas where we can improve. We thank the Editor-in-Chief for the opportunity to re-submit the manuscript as well. Attached you will find the revised manuscript entitled: “Effect of Sex-Specific Running Shoes on Female Recreational Runners” that we hope you find acceptable for publication in the Journal of Applied Sciences. Updates to the manuscript have been highlighted in the revised version.
A really interesting and bold study. The content and research question are valuable to the wider reading audience and the paper is unique in its simplicity. There are a number of typo and grammar errors throughout the manuscript that need to be addressed to ensure that the flow and read of the paper is worthy.
Response: We thank the reviewer for the positive comments. We have gone back through the manuscript and have edited the paper to address the typos and grammar errors.
Introduction:
The last line of the abstract adds nothing to the discussion or conclusion. I strongly suggest that it is removed.
Response: We agree with the reviewer and the last line has been removed from the manuscript and no longer appears in LL 22 of the manuscript.
Running shoe design has evolved rather than changed, there are not so many differences in designing the shoe. They all have a sole, a lacing mechanism etc..
Response: We agree with the reviewer and the word “changed” has been revised to “evolved” in LL 27 of the manuscript.
The second paragraph looking at associating pathology to shoe design needs to be altered, I would suggest that the team look at making the association between biomechanical outcomes, pathology and shoe design much clearer as it stands this is currently confusing and inaccurate. For instance the heel to toe drop is nothing to do with the amount of cushioning under the heel and forefoot but is a measure of difference in height of the sole unit in these areas. There is also a weak association between pathology and shoe design, A recent paper indicates that those who have plantar heel pain wear stiffer soled shoes than those who don't. Landorf, K.B., Kaminski, M.R., Munteanu, S.E., Zammit, G.V. and Menz, H.B., 2022. Activity and footwear characteristics in people with and without plantar heel pain: A matched cross‐sectional observational study. Musculoskeletal Care.
Response: We thank the reviewer for these comments and references. Our intent with this paragraph was not to associate pathology to shoe design. We apologize for the confusion and misinterpretation. Rather, we were attempting to highlight past shoe design research while attempting to point out the need for our study. Again, the purpose of our study was to simply identify any biomechanical or physiological difference between a shoe that was specifically designed for women and a shoe that was specifically designed for men. We have attempted to edit the paragraph so as to make it less confusing.
We agree that the link between the shoe design and pathology was presented too strongly. This section has been altered to temper the connection between the two. We included the referenced paper from the reviewer and added additional lines to show that the link between shoe design and biomechanics has been shown, but the carry-over to pathology is still weak and not well understood in paragraph 3. LL 40-53 and 51-54.
If the team are looking to link the possible association between injury, outcome measures and shoe design it needs to be a suggestive way rather than so blunt and direct.
Response: We thank the reviewer for this suggestion. We feel that the reworking of the paragraphs, as explained previously, addresses this concern.
Line 64 - which running shoe company? Altra?
Response: We have edited Line 68 as to identify the running shoe company as Altra.
Methods:
Line 80 doesn't make sense
Response: We have edited Line 86-87 to make more sense. It now reads:
“This study was approved by the Utah Valley University Institutional Review Board (IRB log number 439).”
Indicate in the methods what the differences in the shoe were – Is there actually are any difference in key shoe features or are the two shoes tested just marketed at male and females ? Information to include could be based on the footwear assessment tool by Barton et al 2009 Barton, C.J., Bonanno, D. and Menz, H.B., 2009. Development and evaluation of a tool for the assessment of footwear characteristics. Journal of foot and ankle research, 2(1), pp.1-12.
Response: We have edited the methods to now include information regarding shoe characteristics. Line 93-110 now states:
“Ten pairs of shoes were utilized in this research project. The male shoe sizes ranged from 7.0-9.5 US (40-43 Europe) and the female shoe size ranges were from 8.5-11 US (39-42 Europe). We ensured that each female shoe size had a corresponding male shoe size in order to make accurate comparisons. From industry standard sizing charts, the corresponding female shoe to the male shoe is identical in shape and size. Tread patterns were identical between the two shoes. Regarding design differences, the Altra female shoe is marketed as being specifically designed for women with their trademarked “FIT4HER” technology. According to Altra, this technology specifically addresses the unique sex in the female foot as stated on their website [25]. The female shoe has a narrower heel, longer arch, and an altered angle of the footpad under the metatarsal heads compared to the male shoe. In addition, the male and female shoe molds differ in that the male shoe width is built on a D width from heel through midfoot and a 2E toe box. The female shoe is built on a B width from heel through midfoot and with a D-E toe box. The insole (5mm) and stack height (28 mm) are completely identical for both shoes according to the Altra website. Lastly, the female shoe weighs 241 g and the male shoe weighs 286 g [25, 26]
Was the comfort scale just literally one question - do the shoes feel comfortable? If so, this is not how other studies have assessed comfort - Mundermans scale with a multi faceted approach is mostly used. Just a one dimension overall NRS is not a full view of the comfort of the shoe.
Response: We thank the reviewer for pointing out this discrepancy and providing a reference. You are correct, we did not use a comfort scale such as the one described in Mundermann’s paper. However, we respectfully contend that we used a visual analog scale which, according to Mundermann’s paper, has been successfully used in past research such as in countless published exercise physiology protocols where they used the Borg scale to assess one dimension of perceived exertion. As we were not aware of the scale described in Mundermann’s paper at the time of the study we respectfully contend that our one-dimensional visual analog scale can and has been successfully used in past published research. We have edited our language to reflect that we used a visual analog scale:
“Perceived comfort was assessed by utilizing a visual analog scale (VAS) from 1 to 10.” Line 124
Additionally, we have addressed this as a limitation of the study. Line 232-235, specifically states:
“One of the main limitations of the study was the assessment of comfort perception. A single-question VAS was used to determine participant level of comfort; however, this method did not provide a full view of participant comfort. Future use of Mündermann’s multi-faceted approach would provide greater insight into running shoe comfort.”
Results:
Why was only right leg used?
Response: For clarification, this sentence has been moved to the methods section and now states. “The dominant leg variables were compared between subjects to produce all tables and graphs.” LL 128-129
Discussion
Lines 156 - 170 looking at heel stack and GRF - what was the heel stack on this shoe was there a difference between the two shoes - the team are not discussing the results here but repeating and extending the introduction. You haven't computed PFjt force, so why is it being discussed.
Response: This section has been updated to report the lack of differences in heel-to-toe drop on the shoes in this study. We did choose to include the reference to Pfjt forces as they have been shown to be elevated in female runners. We added additional lines to show a need to target female-specific biomechanical alterations and how the shoes in the current design are not different in the areas that have been shown to alter these variables for female runners. LL: 195-201
The main limitation of this manuscript is the lack of assessment and discussion about the two shoes tested. The reason for no difference between each condition could be that there are no differences between the shoes, they are purely marketed at women or men.
Response: We agree with the reviewer and recognize that we did not address the specific differences in the tested shoes. We have updated to include very specific differences in shoe designs and also in parts of the introduction and discussion to suggest the purpose was to see if these shoe differences were enough to elicit differences, which we found they were not. These changes were made in the methods (line 93 - 110), and the discussion in multiple locations (lines 177 – 179, 195 - 200, and 232 – 235).
Expand this part of the manuscript to indicate what the differences were, even to exploit Altra in any claims they make between the two types of shoe. For instance the womens shoe is lighter by 40g, but are other features are the same.
Response: See the response above regarding more specific differences in these shoes and the findings resulted.
Round 2
Reviewer 1 Report
All my comments have been incorporated and questions answered. I have no further comments.
Author Response
Thank you for your time.
Reviewer 2 Report
Thank you for clarifying the points made by my first review, the paper is clearer now and has less ambiguity.
Regarding the paragraph added to the methods, describing the shoe features. Although this expands significantly on the previous version there is a huge bias of information as the details given are what Altra state for their shoe design. An independent assessment of the shoe as per a validated tool, ie: Barton et al, would give a judgement on the differences. What measures did the research team do to assess the differences in the shoe or was it just taken as "different" as Altra say so? There is an opportunity here to provide independent review of the shoes and give specific details on the footwear tested.
The discussion has been improved and reads as a better review of the results. There is room for a stronger discussion exposing the misleading marketing of these shoes.
Author Response
Regarding the paragraph added to the methods, describing the shoe features. Although this expands significantly on the previous version there is a huge bias of information as the details given are what Altra state for their shoe design. An independent assessment of the shoe as per a validated tool, ie: Barton et al, would give a judgement on the differences. What measures did the research team do to assess the differences in the shoe or was it just taken as "different" as Altra say so? There is an opportunity here to provide independent review of the shoes and give specific details on the footwear tested.
Response: Thank you for the suggestion to include the validated tool for shoe assessment. Some of the methods of the Barton et al. study were not applicable such as wear patterns, age of the shoe, etc. as these were all brand new lab shoes. We did go through the assessment and measured those things that were readily available for us to measure via our experience and equipment to test. These measurements are now reported in the methods in addition to the reported differences from Altra. We feel that, as you suggested, this gives the readers a clearer picture of the shoe differences.
The discussion has been improved and reads as a better review of the results. There is room for a stronger discussion exposing the misleading marketing of these shoes.
Response: We reviewed marketing claims from Altra on their website as well as in articles that we could assess on the web. While Altra does claim benefits to their zero drop technology and footpad width to name a few, those components were all identical in the men’s and women’s versions of the shoe. Altra’s claims about these shoes from a marketing standpoint were only that the shoe was meant to be different and fit the unique morphology of a women’s foot measured in previous research studies. We could not find anywhere a marketing piece directed at improvements in running economy or biomechanics with these shoes. We did add lines in the final concluding paragraph to further emphasize that they marketed these shoes as trying to fit a women’s foot, but that the differences were not substantial or meaningful enough to cause changes in running biomechanics and physiology.
