Isokinetic Dynamometry as a Tool to Predict Shoulder Injury in an Overhead Athlete Population: A Systematic Review

Reviewer’s comments

Author’s reply

Reviewer 1

1) Shoulder injuries is a broad categorisation - really an anatomical region rather than specific injuries. The argument is made for the muscular strength and endurance of shoulder internal and external rotational movements

While these are no doubt important for certain injury etiologies they arguably have no relationship with others. It is not clear to me how distinctions are made in your systematic review. For example you have swimmers (relatively slow repetitive concentric actions), volleyballers and cricket bowlers (isolated high velocity actions with eccentric decelerations) and rugby league and handball (multiple actions with high risk of impact injuries/collisions).

✓   We thank Reviewer 1 for his/her review of our manuscript.   We agree with Reviewer 1 that injuries can be broadly categorized by anatomical region however our previous studies and other research commonly reports anatomical region(s) (separate or combined), mechanism(s) of injury, location or classification (musculoskeletal, kin, joint, etc.) incidence and severity ^1,2. We acknowledge the author’s comments around the diversity of sports and actions included in this review. The broad nature of this literature review was not limited to one sport but to all upper limb dominant sports as there was not enough literature available to conduct a more specific systematic review at this time.

Our inclusion of research findings with swimmers, volleyball, cricket bowlers and handball (all with varying limb velocities as noted by Reviewer 1) was to  broadly associate to surfing (this was a preliminary study for a follow up cross-sectional manuscript on surfers and shoulder isokinetic dynamometry also submitted to Sports and currently under review). Surfing is an upper body dominant aerobic/anaerobic activity with other similar activities which there is little research on.

As noted by this literature review, there is limited research available conducted on isokinetic dynamometry and its association to shoulder injury and even less when a specific sport is selected. Therefore there is inadequate literature currently available to complete a systematic review on surfing, swimming, or any individual upper limb dominant sport using isokinetic dynamometry in association to injury.

With regard to rugby league/handball and high risk of impact we argue that surfers do indeed experience impact, both from striking the seafloor or sea surface (18%), struck by their own board (36.7% - 73.4%, depending upon the data source, emergency department or survey data) or struct by another surfers board (~6.5%) ².

1.     Furness et al., (2015).  Acute injuries in recreational and competitive surfers: incidence, severity, location, type, and mechanism.  Am J Sports Med. 43(5). 1246-1254.

2.     McArthur et al., (2020). Epidemiology of Acute Injuries in Surfing: Type, Location, Mechanism, Severity, and Incidence: A Systematic Review. Sports. 8(2):1-25.

2. No real rationale for IR:ER strength, endurance relationships is provided - I believe that readers should be offered some explanation/rationale for the study purpose and search criteria. The concentric acceleration and eccentric deceleration muscular actions also would benefit from discussion - some of your reviewed manuscripts have included data on these suggested functional deficits

✓   We agree with Reviewer 1’s comment with regard to expanding the rationale for our study and we have amended our manuscript accordingly.

We have provided further rationale on lines 89-93 stating, “

The IR:ER strength, endurance relationship is further discussed in our discussion on lines 40-48;  however, it was not the purpose of this review to study the physiological reason for the development of injury but rather to find associative or predictive factors. As the studies were heterogeneous in their protocols (i.e. concentric and/or eccentric, angles and speeds) we cannot further develop the second sentence from the reviewer in this study and this has been included as a limitation and recommendation for future research to follow uniform procedures and set-ups.

 In brief, isokinetic evaluation of the shoulder is used to assess function stability and the muscular strength/endurance of the shoulder musculature. Lines  59-62 have been amended to clarify: “The evaluation of the shoulder is often used to assess functional stability, dynamics and muscular performance (strength, speed and endurance) in sports that are predominantly overhead.  Additionally, isokinetic dynamometry evaluation has also been used to determine profiles or athletes and patients who demonstrate shoulder abnormalities and used in clinical decision making and rehabilitation.”

Noffal GJ (2003).  Isokinetic eccentric-to-concentric strength ratios of the shoulder rotator muscles in throwers and non-throwers. Am J Sports Medicine. 31: 537–541. 

•  Batalha et al., (2020).  The Effectiveness of a Dry-Land Shoulder Rotators Strength Training Program in Injury Prevention in Competitive Swimmers. J of Human Kinetics. 71:11-20. 

3) Given that the studies cited seemed to have assessed IR and ER in various ways, I wonder whether descriptors and discussions should refer only to these movements and avoid suggesting specific muscle groups - which arguably can not be isolated for these movements - e.g. internal and external rotator shoulder muscles

✓ We agree with Reviewer 1 and have made appropriate amendments to the manuscript (where all IR & ER muscles are referred to were changed to movement).

4)         There were notable differences in the studies for elements such as positioning for IR/ER assessment, isokinetic speeds utilised, and the mix of concentric and eccentric actions - these perhaps should be included with limitations.

✓   We agree with Reviewer 1 and have included these differences in the Limitations section of our manuscript.

An additional line has been added (lines 95-97), this now reads: “An additional limitation to both study inclusion and comparison is the variability in the methods in which IR and ER were assessed. For example, the seat setting, shoulder positioning, movements (eccentric and/or concentric) isokinetic speeds were not always specified or varied between studies.”

Minor Points/typographical questions: L 39 ‘through fluctuating its resistance.’ - does it really - not my understanding of isokinetic dynamometry

✓   We have amended this sentence to better and deleted the term “fluctuating its resistance”.

l57/58 As the primary muscles used in throwing and swimming sports are the rotator cuff muscles - they undoubtedly play a role in control and joint stability, but they are certainly not prime movers for these kinds of actions

✓   Our use of the term “primary” in this sentence does not refer to “primary movers”, we had amended this sentence and removed the word “primary” to avoid any confusion.

L 69 previously mentioned above. - one of those words seems redundant

✓   We have amended that sentence so the word “coach: does not appear twice.

L 99 google scholar ? Capitalisation

✓   We have corrected to Google Scholar

Reviewer 2

We thank Reviewer 2 for his/her review of our manuscript.

Introduction: Lines 34-41: I feel that these sentences are disconnected. Please, try to ‘connect’ the information presented.

✓   We have amended these lines to flow better

Lines 42-44: Please rewrite to improve clarity.

✓   We have amended these lines to flow better

Lines 51-52: Please rewrite to improve clarity.

✓   We have amended this sentence to improve clarity

Please provide a better rationale for the study

✓   We have amended our rationale for the study to include:

“Following a thorough and extensive review of the literature, there is currently no systematic review specific to strength measurements of shoulder IR and ER using isokinetic dynamometry and IR, ER and IR : ER ratios and association with injury. Given the high rate of shoulder injury across a variety of overhead predominant sports, assessment of IR and ER via isokinetic dynamometry may provide valuable insight into injury prevention.”

Methods:  Was the study protocol registered in PROSPERO? Please, clarify.

✓   The protocol was developed prospectively prior to data extraction and critical appraisal; however, it was not registered within an online registry such as Prospero.

Added to lines 135-136 in methods

Line 112: eligibility criteria were discussed. Please, correct.

✓   We have amended the text as recommended by Reviewer 2

Line 254: rest a period: please correct to ‘resting period’.

✓   We have amended the text as recommended by Reviewer 2

Line 298: please clarify which studies were disregarded.

✓  We understand that the Reviewer is requesting the specific studies which did not meet significant findings with a low sample size. From 2.8 Assessment of Sample Size in the amended manuscript, we would like to clarify the following:

“However, articles that did not detect a statistically significant relationship and had a sample size that did not meet requirements laid out by Hsieh et. al [37] were removed due to the having a sample size too small to truly detect differences between groups (Table 6).”

Hsieh is not an article included in our review (as outlined in the  PRISMA selection of studies flow diagram); it is the reference used to cite ‘adequate’ sample size criteria. 

i.e. only one article had over 100 participants, and any one study could have measured strength, endurance and ratios and only found significant findings in one of these outcome measures (hence an * (asterisk) sign in the data extraction table (T. 4) and inclusion in our final table (T.6) --- We did not include findings that did not show significance (P>0.05) AND had an inadequate sample size- (T. 6). 

There was a mistake in the table referenced attached to this comment (this has been changed from Table 5 to Table 6)

Table 6 compares the results after separating cross-sectional and prospective cohort studies, after the removal of non-significant findings in articles that did not reach the participant requirement outlined by Hsieh[37]. This simplistic view makes it easier to view the statistically significant evidence and the relationships between the studies.

Results:  Please modify Table 4 according to the journal Instructions for authors

✓ Table 4 has been changed from Landscape to Portrait

Reviewer 3

The abstract not successfully compiling and summarizing focal points of this study

✓   We wish to thank Reviewer 3 for their review of our manuscript.

The authors were not successfully provide adequate rationales for their comments in many of sentences especially when they commented about the selection of subjects and methodology part. It is too brief and doesn’t provide quality justification of the purpose statement.

✓   We have amended the manuscript to improve the rationale for our study.

Validity issue – your study is not successful to provide validity evidence of your measurement issues. I am not really convinced to your findings and not clear about what would be potential lessons from reading your study.

Justification:  it was not the purpose of our study to validate Isokinetic Dynamometry, rather to complete a systematic review on its use with regard to athletes who are involved in a predominantly overhead sport. Authors used a systematic approach and rigorous methodology using the PRISMA statement guideline. Additionally, two independent reviewers utilized the CASP and AXIS appraisal tools which followed a high-quality assessment of methodological quality.

 Our findings indicate that low isokinetic endurance of the shoulders (IR) and low strength ratios were predictors of injury, which will assist strength and conditioning coaches and rehabilitation specialists in both prevention and rehabilitation.

The findings of this study can assist in determining what factors need to be accounted for when using isokinetic dynamometry testing to ensure high-quality test-retest reliability and we have shown that high-quality prospective research shows strong evidence that upper limb dominant athletes with lower endurance measurements for internal rotation and low strength ratios IR:ER developed a shoulder injury in their sporting season.

Please check and re-confirm and have other experienced scholars to read your manuscript prior to “submission” in terms of “research process” and conclusion part. Your current conclusion is still too brief and not really meaningful.

Justification:  the senior authors are widely published and can assure Reviewer 3 that the manuscript was thoroughly read and appropriate edits made before submission.   We have however, re-read the manuscript and made subtle edits throughout.

Finally authors, please should considerer to include some of the following references

[1]      C. Calvo-Lobo, S. Pacheco-da-Costa, J. Martínez-Martínez, D. Rodríguez-Sanz, P. Cuesta-Álvaro, D. López-López, Dry Needling on the Infraspinatus Latent and Active Myofascial Trigger Points in  Older Adults With Nonspecific Shoulder Pain: A Randomized Clinical Trial., J. Geriatr. Phys. Ther. 41 (2018) 1–13. https://doi.org/10.1519/JPT.0000000000000079.

[2]      C. Calvo-Lobo, S. Pacheco-da-Costa, E. Hita-Herranz, Efficacy of Deep Dry Needling on Latent Myofascial Trigger Points in Older Adults  With Nonspecific Shoulder Pain: A Randomized, Controlled Clinical Trial Pilot Study., J. Geriatr. Phys. Ther. 40 (2017) 63–73. https://doi.org/10.1519/JPT.0000000000000048.

[3]        C. Calvo Lobo, C. Romero Morales, D. Rodríguez Sanz, I. Sanz Corbalán, E.A. Sánchez Romero, J. Fernández Carnero, D. López López, Comparison of hand grip strength and upper limb pressure pain threshold between  older adults with or without non-specific shoulder pain., PeerJ. 5 (2017) e2995. https://doi.org/10.7717/peerj.2995.

Justification:  Reviewer 3 has recommended the inclusion of three references. Unfortunately, after looking into these references, the first two studies are not related to our present study/manuscript and none of which meet our inclusion criteria.

Please refer to our inclusion criteria: on lines 155- 167, specifically, “Studies included needed to utilise isokinetic dynamometry as an intervention and be either observational design (prospective or retrospective cohort study or cross-sectional study) to ensure all existing literature meeting the aim would be reviewed. Additionally, studies needed to examine shoulder strength and/or endurance, include shoulder IR and ER as a measurement outcome and either analyse the risk of injury (prospective or retrospective cohort) or compare uninjured versus uninjured participants (cross-sectional). Any study not meeting the inclusion criteria or that only profile strength values or injuries in a sporting population and did not link outcomes to injury were excluded.”

However, our current paper in development which is investigating IR and ER strength profiles in surfers with a current (or past) shoulder injury is a good fit for the Calvo-Lobo et al., (2017) paper (PeerJ) and we thank Reviewer 3 for bringing this publication to our attention as we will incorporate it into our manuscript in progress.