Shoulder extension strength: a potential risk factor for shoulder pain in young swimmers?

Identifying evidence-practice gaps for shoulder injury risk factors in competitive swimmers: uniting literature and expert opinion

OBJECTIVES

To identify evidence-practice gaps regarding shoulder injury risk factors in competitive swimmers.

METHODS

We gathered insights from 27 swimming experts including elite swimmers, coaches, high-performance staff and applied researchers using Concept Mapping. Participants brainstormed, sorted and rated (from 1 (least) to 10 (most) important and modifiable) their ideas of shoulder injury risk factors in competitive swimmers. Proposed risk factors rated above the grand mean for importance (6.2±0.4) or modifiability (6.5±0.5) ratings were considered highly important/modifiable. Expert opinions were then juxtaposed with systematic review findings to identify overlaps or convergences.

RESULTS

Brainstorming generated 126 proposed shoulder injury risk factors for competitive swimmers, subsequently refined to 61 unique proposed risk factors by removing duplicates and combining similar responses. The participants sorted the 61 risk factors into seven distinct clusters. Experts perceived 36/61 proposed risk factors as highly important, of which 6 were supported by literature, 6 showed no association with injury, 2 had conflicting evidence and the remaining 22 have not yet been investigated, suggesting an evidence-practice gap. Three proposed risk factors 'inconsistent training load', 'poor stroke technique' and 'low posterior shoulder strength-endurance' exhibited high perceived importance, high perceived modifiability and supporting evidence.

CONCLUSION

An evidence-practice gap was identified for 28 proposed risk factors perceived as highly important by swimming experts despite either (1) no relevant empirical research (n=22), or (2) no association with injury (n=6) from synthesised evidence. Greater collaboration between researchers and practitioners is needed to effectively address shoulder injury risk factors in competitive swimmers.

Clinical and ultrasound findings of 'swimmer's shoulder' and its association with training history in elite Portuguese swimmers: a cross-sectional study

OBJECTIVES

To assess the prevalence of shoulder injuries and ultrasound findings in elite Portuguese swimmers and their association with symptoms and personal or training-related factors.

METHODS

This cross-sectional study was conducted at the Portuguese Open and Youth Swimming National Championships between 27 and 30th July 2022. Each athlete entered details regarding personal and training history into a questionnaire and underwent a physical and ultrasound shoulder examination.

RESULTS

A total of 102 swimmers out of 662 Portuguese athletes were included in the study. Shoulder pain experienced during the previous season was reported by 42% of the athletes. A high prevalence of shoulder structural abnormalities was noted, specifically supraspinatus tendinosis (91%), tears (29%), and subacromial bursitis (29%). Specific training for injury prevention was associated with higher rates of infraspinatus tendinosis (p = 0.047), and supraspinatus tears were linked to greater swimming distances per week (p < 0.001) and practice (p < 0.001), more years of practice (p = 0.018), shoulder pain at the time of evaluation (p = 0.023), a higher number of missed competitions (p = 0.041), and shoulder injections (p = 0.009). Subacromial bursitis was associated with shoulder pain at the time of evaluation (p = 0.002) and during the previous season (p < 0.001), missed competitions (p < 0.001), and requirement for physical therapy (p = 0.006).

CONCLUSIONS

A high prevalence of shoulder morphological changes was found in surveyed swimmers and there were several associations with training load, regardless of individual characteristics of each athlete. It is essential to understand the true impact of current injury prevention programs and to develop effective measures to protect swimmers' health.

Sink or Swim? Clinical Objective Tests and Measures Associated with Shoulder Pain in Swimmers of Varied Age Levels of Competition: A Systematic Review

BACKGROUND

Swimming is enjoyed by athletes of all ages, and shoulder pain is a common problem. Clinicians identify impairments which impact shoulder pain and these impairments may differ depending on the swimmer's age competition level.

PURPOSE

The purpose of this study was to investigate objective measures utilized to assess swimmers and assess the relationship of test values to shoulder pain in distinct age groups/competition levels. A secondary aim was to report normative/expected values for these tests.

DESIGN

Systematic review.

METHODS

PRISMA methodology was employed to assess studies evaluating clinical tests and measures associated with shoulder pain for swimmers in varied age competition levels. The Methodological Index for Non-Randomized Studies instrument was used to evaluate the quality of the included studies, and a qualitative synthesis of findings was conducted to determine the strength of the evidence in four age competition levels for nine objective measures. Distinct cut points for proposed measures were identified.

RESULTS

Twenty-seven studies were included in the analysis and the majority were of moderate quality in adolescent/adult swimmers. Youth swimmers had limited evidence for the development of shoulder pain associated with scapular position/dyskinesia, weakness of periscapular muscles, low endurance of core muscles, and moderate evidence for shoulder pain associated with laxity and altered range of motion (ROM). Adolescent/adult swimmers demonstrated limited evidence for a positive association between developing shoulder pain if there is a low eccentric ER:concentric IR ratio, and moderate evidence for pectoralis minor tightness and glenohumeral laxity. There were limited studies regarding masters swimmers to derive conclusive evidence. Cut points were identified from the included studies but these have not been validated in other studies.

CONCLUSION

Swimmers of various ages may have different objective clinical tests and measures associated with the risk for developing shoulder pain. More studies are needed to fully understand risk factors for shoulder pain in the masters swim competition level, and to validate recommended cut points for various tests and measures.

Key level of evidence

3, Systematic review of mostly Level 3 studies.

Shoulder structures and strength in competitive preadolescent swimmers: A longitudinal ultrasonographic study

BACKGROUND

Repetitive shoulder movements during competitive training may cause changes in the strength of periarticular shoulder structures in preadolescent swimmers.

OBJECTIVE

To prospectively determine the effects of training on shoulder periarticular structures and muscle strength in preadolescent swimmers.

DESIGN

Prospective cohort study.

SETTING

Community-based natatorium.

PARTICIPANTS

Twenty-four preadolescent swimmers aged 10-12 years.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Measurements were repeated in three periods as preseason, midseason, and postseason. Ultrasonographic measurements (supraspinatus tendon thickness, humeral head cartilage thickness, deltoid muscle thickness, and acromiohumeral distance) were performed using a portable device and a linear probe. Shoulder (flexion, extension, abduction, internal and external rotation) and back (serratus anterior, lower, and middle trapezius) isometric muscle strength were measured with a handheld dynamometer.

RESULTS

Supraspinatus tendon thickness and acromiohumeral distance were similar in all periods (all p > .05); however, deltoid muscle and humeral head cartilage thicknesses increased throughout the season (p = .002, p = .008, respectively). Likewise, whereas shoulder muscle strength increased (all p < .05), back muscle strength was similar in all periods (all p > .05).

CONCLUSIONS

In preadolescent swimmers, acromiohumeral distance and supraspinatus tendon thickness seem to not change; but humeral head cartilage and deltoid muscle thicknesses as well as shoulder muscle strength increase throughout the season.

Posterior deltoid shoulder tightness and greater contralateral lower limb muscle strength are associated with swimmers' shoulder pain

OBJECTIVES

To identify factors associated with shoulder pain in swimmers based on elastic muscle modulus, joint range of motion, and isometric muscle strength.

DESIGN

Cohort study.

METHODS

Forty-eight competitive swimmers without shoulder pain (age: 18-28 years; men: 29) were followed-up for 6 months. Baseline measurements of the elastic modulus of the pectoralis minor, supraspinatus, infraspinatus, posterior deltoid, and pectoralis minor muscles were obtained using shear wave elastography. Range of motion and isometric strength were measured using a goniometer and a hand-held dynamometer, respectively. A questionnaire was administered weekly for 6 months to determine shoulder pain occurrence. Each item was compared between shoulders with and without pain at baseline. For participants with shoulder pain exceeding 2 weeks, shear wave elastography and range of motion at baseline (pre pain) and during follow-up (post pain) were compared.

RESULTS

Of 46 swimmers followed-up for 6 months, 20 reported shoulder pain. 14 swimmers with pain were evaluated twice. Participants with shoulder pain during follow-up had significantly higher posterior deltoid and pectoralis minor stiffness at baseline and high lower extremity isometric muscle strength contralateral to the shoulder with pain compared to those without pain (p < 0.05). Swimmers with pain exceeding 2 weeks exhibited no differences in ultrasound shear wave elastography and range of motion at baseline and after pain onset.

CONCLUSIONS

Posterior deltoid and pectoralis minor muscle stiffness, and high isometric lower extremity strength contralateral to the shoulder with pain may be associated with shoulder pain development, thereby indicating the importance of maintaining posterior deltoid and pectoralis minor muscle flexibility during conditioning.

Shoulder pain and injury risk factors in competitive swimmers: A systematic review

AIM

To synthesize and assess the literature for shoulder pain and injury risk factors in competitive swimmers.

DESIGN

Systematic review with best-evidence synthesis.

DATA SOURCES

CINHAL, SportDiscus, Scorpus, PubMed, and Embase databases from 1966 to April 30 2022.

SEARCH AND INCLUSION

Cohort, cross-sectional, and case-control studies investigating shoulder pain or injury risk factors in competitive swimmers were included. Quality of eligible studies were assessed using a modified Newcastle-Ottawa scale. Risk factors were divided into four categories: modifiable-intrinsic, modifiable-extrinsic, non-modifiable, and other/secondary.

RESULTS

Of 1356 studies identified, 24 full texts were evaluated for methodological quality, 22 met the criteria and were included in best evidence synthesis. There was no strong evidence supporting or refuting the association between 80 assessed variables and shoulder injury or pain. The swimmers' competitive level (nondirectional), and shoulder muscle recruitment profiles (e.g., increased activity of serratus anterior) exhibited moderate evidence supporting an association. Conversely, internal and external range of motion, middle finger back scratch test, training frequency, specialty stroke, height/weight, sex, and age all had moderate evidence opposing an association. Limited evidence was found for 58 variables, and conflicting for 8. The highest quality study (n = 201) suggested high acute-to-chronic workload ratio and reduced posterior shoulder strength endurance are associated with injury.

CONCLUSIONS

Due to the paucity of high-quality studies, future prospective studies are needed to reevaluate known risk factor associations over exploring additional potential risk factors. Swimming practitioners should be aware of the nondirectional association of a swimmer's competitive level and pain, as squad changes could impact injury incidence. Moreover, swimmers experiencing shoulder pain may show increased activity in shoulder stabilizers during specific movements. Importantly, shoulder strength-endurance may be the most clinically relevant modifiable intrinsic risk factor.

Validity and Reliability of the Kinvent Handheld Dynamometer in the Athletic Shoulder Test

CONTEXT

Long-lever shoulder strength tests may aid clinical decision-making regarding return to sport after a shoulder injury. The Athletic Shoulder Test (AST) was developed to measure force production in 3 positions of shoulder abduction (90°, 135°, and 180°) using force plates. However, handheld dynamometers (HHDs) are more portable, affordable, and may provide valid and reliable results which would increase the clinical utility of long-lever tests. HHDs vary in shape, design, and their capacity to report parameters such as rate of force production and require further investigation. The aim of this study was to examine the intrarater reliability of the Kinvent HHD and assess its validity against Kinvent force plates in the AST. Peak force (in kilograms), torque (in Newton meters), and normalized torque (in Newton meters per kilogram) were reported.

DESIGN

Validity and reliability study.

METHODS

Twenty-seven participants with no history of upper limb injury performed the test in a randomized order using the Kinvent HHD and force plates. Each condition was assessed 3 times, and peak force was recorded. Arm length was measured to calculate peak torque. Normalized peak torque was calculated by dividing torque by bodyweight (in kilograms).

RESULTS

The Kinvent HHD is reliable when measuring force (intraclass correlation coefficient [ICC] ≥ .80), torque (ICC ≥ .84), and normalized torque (ICC ≥ .64) during the AST. The Kinvent HHD is also valid when compared with the Kinvent force plates for force (ICC ≥ .79; r ≥ .82), torque (ICC ≥ .82; r ≥ .76), and normalized torque (ICC ≥ .71; r ≥ .61). There were no statistically significant differences across the 3 trials on analyses of variance (P > .05).

CONCLUSIONS

The Kinvent HHD is a reliable tool when used to measure force, torque, and normalized torque in the AST. Furthermore, given the lack of significant difference between trials, clinicians can use one test to accurately report relative peak force/torque/normalized torque rather than average 3 separate trials. Finally, the Kinvent HHD is valid when compared with Kinvent force plates.

Intrinsic Risk Factors for Noncontact Musculoskeletal Injury in Collegiate Swimmers: A Prospective Cohort Study

CONTEXT

Shoulder pain is pervasive in swimmers of all ages. However, given the limited number of prospective studies, injury risk factors in swimmers remain uncertain.

OBJECTIVE

To determine the extent to which the risk factors of previous injury, poor movement competency, erroneous freestyle swimming technique, and low perceived susceptibility to sport injury were associated with noncontact musculoskeletal injury in collegiate swimmers.

DESIGN

Prospective cohort study.

SETTING

College natatorium.

PATIENTS OR OTHER PARTICIPANTS

Thirty-seven National College Athletic Association Division III swimmers (21 females, 16 males; median age = 19 years [interquartile range = 3 years], height = 175 ± 10 cm; mass = 70.0 ± 10.9 kg).

MAIN OUTCOME MEASURE(S)

Participants completed preseason questionnaires on their previous injuries and perceived susceptibility to sport injury. At the beginning of the season, they completed the Movement System Screening Tool and the Freestyle Swimming Technique Assessment. Logistic regression was used to calculate odds ratios (ORs) with 95% CIs for the association between each risk factor and injury.

RESULTS

Eleven of the 37 participants (29.7%) sustained an injury. Univariate analyses identified 2 risk factors: previous injury (OR = 8.89 [95% CI = 1.78, 44.48]) and crossover hand positions during the freestyle entry phase (OR = 8.50 [95% CI = 1.50, 48.05]). After adjusting for previous injury, we found that a higher perceived percentage chance of injury (1 item from the Perceived Susceptibility to Sport Injury) decreased the injury odds (adjusted OR = 0.11 [95% CI = 0.02, 0.82]). Poor movement competency was not associated with injury (P > .05).

CONCLUSIONS

Previous injury, a crossover hand-entry position in freestyle, and a low perceived percentage chance of injury were associated with increased injury odds. Ascertaining injury histories and assessing for crossover positions may help identify swimmers with an elevated injury risk and inform injury-prevention strategies.

The Effect of Exercise Therapy Interventions on Shoulder Pain and Musculoskeletal Risk Factors for Shoulder Pain in Competitive Swimmers: A Scoping Review

CONTEXT

Shoulder pain is the main cause of missed or modified training in competitive swimmers. Exercise therapy can improve the outcomes, yet uncertainty exists regarding the characteristics of these interventions.

OBJECTIVES

The primary aim was to describe the evidence base relating to the effectiveness of exercise therapy interventions on shoulder pain and shoulder musculoskeletal risk factors for shoulder pain in swimmers. The secondary aim was to identify gaps in the literature and provide recommendations for future research and practice.

EVIDENCE ACQUISITION

A scoping review methodology was applied through the search of MEDLINE, PubMed, Scopus, Web of Science, and CINAHL databases. The authors included any research studies (except clinical commentaries and conference papers) that assess the effect of exercise therapy on shoulder pain and musculoskeletal risk factors for shoulder pain in swimmers. The literature was critically appraised using the Modified Down and Black checklist.

EVIDENCE SYNTHESIS

From 452 papers identified, 14 studies were included in this review. An exercise program of 6 to 8 weeks, including strengthening exercises (shoulder external rotator and scapula retractor muscles) and stretches (pectoral muscles), can decrease the incidence of shoulder pain in swimmers. Furthermore, a combination of exercises and stretches with manual therapy techniques can help to decrease shoulder pain in injured swimmers. Regarding risk factors, a strengthening program of more than 12 weeks increased shoulder external rotation peak force, endurance, and external rotation/internal rotation ratio; however, this was not associated to decreases in pain. Finally, open kinetic chain exercises and a dry-land program are superior to close kinetic exercises and water training for improving shoulder external rotation strength and endurance.

CONCLUSIONS

Exercise therapy has positive effects on reducing the incidence of shoulder pain, the management of shoulder pain, and improving shoulder musculoskeletal risk factors in competitive swimmers. However, due to methodological limitations of the studies, caution must be used when applying these results in practice. Future research should focus on high-quality randomized controlled trials for prevention and management of shoulder pain in swimmers.

The Relationship Between Workload and Non-Contact Musculoskeletal Injury in College Swimmers: A Prospective Cohort Study

CONTEXT

Swimmers are known for high training loads and overuse injuries, but few studies have investigated the relationship between the two at the college level.

OBJECTIVE

To determine the association between workload and non-contact musculoskeletal injury in college swimmers. We hypothesized (1) higher overall workload (kilometers swum throughout the season) would be associated with increased odds of injury and (2) the ratio of the current week's (acute) workload divided by the current month's (chronic) workload (i.e., the acute:chronic workload ratio (ACWR)) would be more strongly associated with odds of injury than acute or chronic workloads alone.

DESIGN

Prospective cohort study.

SETTING

College natatorium.

PATIENTS OR OTHER PARTICIPANTS

Thirty-seven Division III college swimmers.

MAIN OUTCOME MEASURES

Logistic regression using generalized estimating equations was used to calculate odds ratios (OR) with 95% confidence intervals (CI) for injury relative to high workloads and high ACWRs. Injury rates for several ranges of workloads and ACWRs were also calculated.

RESULTS

Eleven participants (29.7%) sustained 12 injuries, with seven injuries occurring during the participants' winter training trip. Injury was associated with high acute workloads (OR = 27.1 [95% CI = 8.2, 89.8]) and high ACWRs (OR = 25.1 [95% CI = 7.7, 81.4]) but not high chronic workloads (OR = 2.6 [95% CI = 0.3, 20.0]) or overall workloads (OR = 1.00 [95% CI = 0.99, 1.01]). High acute workloads (>37.2 km/week) and high ACWRs (>1.56) increased injury rate from ≤1% to 15% and 14%, respectively, compared to all lower acute workloads and ACWRs.

CONCLUSIONS

College swimmers can tolerate high workloads spread out over the season. However, caution should be used when prescribing high acute workloads and high ACWRs (e.g., winter training trip) due to increased odds of injury.

Prediction of Shoulder Pain in Youth Competitive Swimmers: The Development and Internal Validation of a Prognostic Prediction Model

BACKGROUND

Knowledge of predictors for shoulder pain in swimmers can assist professionals working with the athlete in developing optimal prevention strategies. However, study methodology and limited available data have constrained a comprehensive understanding of which factors cause shoulder pain.

PURPOSE

To investigate risk factors and develop and internally validate a multivariable prognostic model for the prediction of shoulder pain in swimmers.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

A total of 201 pain-free club- to international-level competitive swimmers were followed for 2 consecutive seasons. The cohort consisted of 96 male (mean ± SD age, 13.9 ± 2.2 years) and 105 female (13.9 ± 2.2 years) swimmers. Demographic, sport-specific, and musculoskeletal characteristics were assessed every 6 months. Swim-training exposure was observed prospectively. Shoulder pain interfering with training was the primary outcome. Multiple imputation was used to cope with missing data. The final model was estimated using multivariable logistic regression. We applied bootstrapping to internally validate the model and correct for overoptimism.

RESULTS

A total of 42 new cases of shoulder pain were recorded during the study. Average duration of follow-up was 1.1 years. Predictors included in the final model were acute:chronic workload ratio (odds ratio [OR], 4.31; 95% CI, 1.00-18.54), competitive level (OR, 0.19; 95% CI, 0.06-0.63), shoulder flexion range of motion, posterior shoulder muscle endurance (OR, 0.96; 95% CI, 0.92-0.99), and hand entry position error (OR, 0.37; 95% CI, 0.16-0.91). After internal validation, this model maintained good calibration and discriminative power (area under the receiver operating characteristic curve, 0.71; 95% CI, 0.60-0.94).

CONCLUSION

Our model consists of parameters that are readily measurable in a swimming setting, allowing the identification of swimmers at risk for shoulder pain. Multivariable logistic regression showed the strongest predictors for shoulder pain were regional competitive swimming level, acute:chronic workload ratio, posterior shoulder muscle endurance, and hand entry error.

Swim-Training Volume and Shoulder Pain Across the Life Span of the Competitive Swimmer: A Systematic Review

BACKGROUND

Competitive swimmers are exposed to enormous volumes of swim training that may overload the soft tissue structures and contribute to shoulder pain. An understanding of training factors associated with the injury is needed before practice guidelines can be developed.

OBJECTIVES

To investigate the relationship between swim-training volume and shoulder pain and to determine swim-training volume and shoulder pain prevalence across the life span of the competitive swimmer.

DATA SOURCES

Relevant studies within PubMed, Web of Science, and MEDLINE.

STUDY SELECTION

Studies that assessed the relationship between a defined amount of swim training and shoulder pain in competitive swimmers.

DATA EXTRACTION

Twelve studies (N = 1460 participants) met the criteria. Swimmers were grouped by age for analysis: young (<15 years), adolescent (15-17 years), adult (18-22 years), and masters (23-77 years).

DATA SYNTHESIS

Adolescent swimmers showed the highest rates of shoulder pain (91.3%) compared with other age groups (range = 19.4%-70.3%). The greatest swim-training volumes were reported in adolescent (17.27 ± 5.25 h/wk) and adult (26.8 ± 4.8 h/wk) swimmers. Differences in exposure were present between swimmers with and those without shoulder pain in both the adolescent (P = .01) and masters (P = .02) groups. In adolescent swimmers, the weekly swim-training volume (P < .005, P = .01) and years active in competitive swimming (P < .01) correlated significantly with supraspinatus tendon thickness, and all swimmers with tendon thickening experienced shoulder pain.

CONCLUSIONS

Evidence suggests that swim-training volume was associated with shoulder pain in adolescent competitive swimmers (level II conclusion). Year-round monitoring of the athlete's swim training is encouraged to maintain a well-balanced program. Developing athletes should be aware of and avoid a sudden and large increase in swimming volume. However, additional high-quality studies are needed to determine cutoff values in order to make data-based decisions regarding the influence of swim training.

Low Range of Shoulders Horizontal Abduction Predisposes for Shoulder Pain in Competitive Young Swimmers

The prevalence of shoulder pain (SP) among competitive swimmers is high, and may profoundly restrict their ability to compete. This prospective cohort study investigated the association between 3 blocks of performance factors (anthropometric characteristics, sport experience and training regimen) and the presence of SP. The aims of the present study were: (a): to determine the profile of shoulder flexibility in young swimmers, (b) to analyze whether a restricted range of movement (ROM) could be a predictor of subsequent SP in young swimmers. 24 competitive young swimmers were measured in the 2016 pre-season. Measures of passive maximal shoulder extension (SE), flexion (SF), horizontal abduction (SHAB), abduction (SAB), horizontal adduction (SHADD), external (SER) and internal (SIR) rotation ROMs were taken. SP was prospectively monitored during the subsequent season using questionnaires. The data was analyzed via a binary logistic regression and ROC curves were calculated. At the follow-up, 16 swimmers (50%) had developed unilateral SP. Only reduced SHAB ROM was associated with SP [SP group 36.6° vs. pain-free group 41.5°; p = 0.005, d = -0.96 (moderate effect sizes)]. Using the coordinates of the curves, the angle of SHAB ROM that most accurately identified individuals at risk of developing SP was determined to be 39° (sensibility 0.656 and 0.375 specificity). Swimmers with limited ROM (≤39°) have 3.6 times higher risk of developing SP than swimmers with normal ROM (>39°). This study clearly shows that low range of SHAB is a risk factor for developing SP in competitive young swimmers. In the studied data, a SHAB range of 39° was found to be the most appropriate cut-off point for prognostic screening.