Females Present Different Single-Leg Squat Kinematics and Muscle Activation Strategies than Males Even after Hip Abductor Fatigue

Round 1

Reviewer 1 Report

General comments:

The general topic of this manuscript is of interest and appropriate for this journal.  I find the rationale for the study a bit weak overall, since the authors describe several studies that have already answered the question that they are asking.  The addition of the quadriceps is somewhat novel, but then the fatigue protocol didn’t involve the quadriceps at all.  Another strong concern with he fatigue protocol is that a single bout of the HABD task is unlikely to cause muscular fatigue.  The participants are likely to stop due to lactic acid related muscle burn, but that doesn’t indicate fatigue.  There are also no citations to support the fatigue protocol used.  Overall the discussion is well written but doesn’t add a large amount of new knowledge to the literature in my opinion.

Specific comments:

Line 22:  Suggest adding a purpose statement to the end of the background section in the abstract.

Line 37:  Suggest  “….have been observed in individuals with knee injuries”

Line 113: For the HABD MVICs, please add a statement about if the hip was maintained in a neutral flex/extended position and the direction that the toes were pointing (forward or up) because both of these things can impact activation of the GMEd and TFL.

Line 132:  I don’t think this is a great opening sentence for this section.  Angles weren’t assessed by placing the markers. Suggest rewording to something like “To be consistent with the landmarks used for the frontal place 2D angular measurements marker were placed at…….”

Line 133:  Were participants barefoot or shod?  If shod, did you control the footwear?  What about standardized clothing so electrode interference was minimized?

Line 141:  How much knee flexion were they told to achieve during the SLS?  IF self-selected please describe.

Line 157: By full extension of the hip, do you mean in a neutral position?  Or really with the hip extended behind the body as far as possible?

Line 165:  The description of how the 1RM load was determined is a little unclear.  Could you describe the Lombardi method in more detail?

Line 180:  It isn’t clear what the participants did when they were done with the fatigue protocol. Did they immediately stand and perform the SLS again? This is assumed but needs to be more clearly described in the protocol.  Also indicate an estimated amount of time that passed between the end of the fatigue protocol and the collection of the SLS data. 

Line 182:  data is the plural form.  Use data were.

Line 197: Indicate the landmark used for the apex of the angle

Line 226:  Preference for stating the interaction effects first.  If there are none, then move on to describe the simple main effects. 

Line 234:  Same comment as above.  List interaction results first

Figure 2 and 3: Curious as to your decision to make one set a line graph and the other a bar graph?  Would a consistent display be easier for the reader to interpret?

Line 260:  What data is this statement about lower strength in females based on?  Since you didn’t normalize the 1RM data to body mass you can’t make the direct comparison of Lbs between sexes.

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 2 Report

Summary:

Frontal plane hip and knee joint kinematics were assessed in single leg squat activities before and after a hip abductor fatigue protocol. Hip adductor and knee extensor muscles’ electromyography were also assessed.

Comments:

The authors have presented an idea to assess the frontal plane movement of the hip and knee joints. There are items that the authors must correct and review in this document.

Introduction:

-          Paragraph 1: the first sentence can be restructured to better align with the purpose of the authors’ paper – injury is indicated, however, the authors assessed kinematics and electromyography before and after fatigue

-          In the background information, the authors did not mention anatomical differences, such as Q-angle and anthropometrics, between men and women which may explain muscle activation movement pattern differences

Methods:

-          2.2 Participants: it is unclear what the specific demographic parameters were for determining inclusion in the study. What ages were determined and was there a specific ability required other than familiarity with resistance exercises? Without knowing this information it is difficult to determine the applicability of any results

-          Lines 102-108: were the leg extension MVICs performed with an isokinetic dynamometer? There is no reference or detail to the equipment used

-          Lines 109-119: how was the hip abduction angle measured to ensure the 10 deg position? The authors mentioned cameras, but were there markers used and what type of software was used for the capture of kinematics data? What was the resistance used for the MVIC of the hip abductors?

-          Lines 121-130: what specification were used for the surface EMG collection (band pass width, common mode rejection ratio, dB reading)? Were the electrodes pre-gelled?

-          Lines 131-148: was the sagittal plane range of motion controlled or examined? This would directly influence the frontal plane range of motion being assessed here

-          Lines 157-159: how was the hip fully extended?

-          Lines 172-178: how was the load applied to the leg (was this a weighted cuff or a cable)? What are three consecutive instances? This is too ambiguous to determine

-          Lines 184-189: for the FFT, a non-stochastic signal is required in order to calculate the median frequency. However, the authors indicated that this analysis was performed while performing concentric and eccentric muscle actions of the single leg squat. The median frequency would be used more appropriately during the fatigue protocol (isometric)

-          Lines 195-204: the line from the ASIS to the patella do not provide a true representation for calculating the femoral angle relative to the pelvis. Why was a marker at the greater trochanter not used?

Results:

-          Lines 226-230: if there are statistically significant differences, then only report the p-values

-          Lines 234-241: only provide F-ratios when there are statistically significant differences

-          Lines 245-253: when reporting FFT data, use the actual data, not the relative values. In addition, the median frequency calculations during dynamic movements may not be accurate

Discussion:

-          Lines 295-313: these comparisons between EMG median frequencies and fatigue seem to be moot, as fatigue is best assessed using FFT when performing the isometric action

-           

Overall, the quality of the English Language is presented well. There may be minor items that the authors need to review.

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Figure 2, 3, 4:  Are the lines between the male and female data needed?  Adds visual confusion to the graph and I think they should be removed leaving only the connecting line between the Pre and Post for each sex. 

Author Response

Figure 2, 3, 4:  Are the lines between the male and female data needed?  Adds visual confusion to the graph and I think they should be removed leaving only the connecting line between the Pre and Post for each sex. 

Authors: Thank you for your comment. We were not entirely sure what the reviewer meant by "Lines between the male and female data" as the lines on the figures were only between the pre and post. Based on the second part of the comment we have decided to remove the individual participant data and keep only the average pre and post values for each sex. We hope that this is what the reviewer meant and believes is clearer.