Isokinetic peak torque ratios and shoulder injury history in adolescent female volleyball athletes

Glenohumeral internal rotation deficit in volleyball players with and without a history of shoulder pain

This study aimed to investigate physiological and pathological Glenohumeral Internal Rotation Deficit (GIRD) in volleyball players with and without a history of shoulder pain. Volleyball players with a history of shoulder pain (n = 18) and without a history of shoulder pain (n = 18), who were matched in age, weight, height, BMI, years of experience and frequency of practice were recruited for this cross-sectional study. Shoulder internal and external rotation Range of Motion (ROM) was measured for the dominant and non-dominant shoulders of each participant using a digital inclinometer. Measurements of GIRD, External Rotation Gain (ERG), and Total Range of Motion (TROM) were calculated. There were significantly higher degrees of GIRD in the pain group (15.65⁰) than the no-pain group (9.06⁰) (p=0.004) and significantly higher differences in the TROM in the pain group (16.17⁰) than the no-pain group (10.17⁰) (p=0.007). There was no correlation between the level of pain and the presented ROM adaptations. The study showed that for volleyball players, pathological GIRD should be defined at 10-18⁰ degrees of GIRD that are accompanied by differences in the TROM that exceeds 8⁰.

Risk and protective factors for shoulder complaints in indoor volleyball players: A comprehensive systematic review

OBJECTIVE

This systematic review aimed to answer the question: "What are the risk and protective factors for shoulder complaints (pain, injury, or problem) in indoor volleyball players?".

METHODS

Searches were conducted in electronic databases: PubMed/MEDLINE, Embase, CINAHL, and SPORTDiscus, as well as reference lists of the included studies. We included studies evaluating potential intrinsic and extrinsic factors associated with shoulder complaints in indoor volleyball players of any country, age, sex, and competitive level. The Quality in Prognosis Studies (QUIPS) tool was used to assess the risk of bias.

RESULTS

The risk factors for shoulder complaints in volleyball players were identified through four prospective studies, which exhibited a moderate to low risk of bias. These factors included previous shoulder pain or injury, playing in outside and opposite positions, subacromial bursa thickening, and having an average external rotator (ER) isokinetic eccentric torque lower than the average internal rotator (IR) concentric torque. Protective factors were enhancing shoulder IR and ER isokinetic eccentric strength, being male sex, being older, and maintaining a concentric strength ratio ER/IR within the 0.60-0.75 range.

CONCLUSIONS

This systematic review highlights risk factors that clinicians and researchers should consider when assessing and tracking indoor volleyball players.

Gender-Specific Patterns of Muscle Imbalance in Elite Badminton Players: A Comprehensive Exploration

The high-intensity demands of overhead sports exert significant stress on the bilateral shoulder complex, triggering adaptive kinematics and a distinct strength imbalance between internal and external rotators. The imbalance being referred to in the given statement poses a potential risk for humeral head displacement and puts nearby tendons under tension, heightening the vulnerability to injury. This study aims to assess muscle imbalances in badminton athletes. The first hypothesis (H1) suggests that there are differences in internal and external shoulder rotation movements between dominant and non-dominant segments in badminton players. The second hypothesis (H2) proposes that there are variations in muscle imbalances based on gender among elite badminton players. The objectives are to analyze these differences and explore potential gender-related variations in muscle imbalances. The study seeks to contribute to the understanding of muscle imbalances in badminton athletes and potentially guide training and injury prevention strategies in the sport. Using a cutting-edge Hand-Held Dynamometer (HHD), a cohort of 30 elite badminton players underwent an assessment to uncover any bilateral shoulder rotation strength imbalances during a challenging five second isometric maximum contraction. The participants boasted an average age of 17.4 years and a mean playing experience of 7.23 years. The study revealed a notable difference in the ratio of external and internal strength between the dominant and non-dominant shoulders (p = 0.000). This discrepancy amounted to a striking 27.93% muscle imbalance in external rotation/internal rotation strength ratios, favoring the dominant shoulder. Moreover, gender-specific differences were detected, with male players exhibiting a 24.54% muscle imbalance in favor of the dominant shoulder, while female players showcased a more substantial 31.33% imbalance (p = 0.000). In light of these findings, it became evident that elite badminton players possess considerably stronger dominant shoulders compared with their non-dominant counterparts. Furthermore, the study revealed that male players experience less muscular imbalance than their female counterparts.

External to internal glenohumeral strength ratio in non-traumatic rotator cuff pathologies

Background and study aims

A correct agonist -antagonist strength relationship for shoulder external and internal rotation is necessary for functional stability of the shoulder. This strength relationship is described by the ratio of external to internal strength (ER/IR).The aim of this stydy is to produce comparative data as regards the ER/IR ratio in subjects with different non-traumatic rotator cuff diseases.

Design and setting

A cross-sectional study in an outpatient clinic in a tertiary care university hospital.

Methods

In 55 subjects with rotator cuff disease (confirmed by physical examination and assessed by ultrasound and magnetic resonance arthrography), the ER/IR ratio of the shoulder was isometrically measured with a hand-held dynamometer and compared with values pertaining to the unaffected shoulder of the same individuals.

Results

The mean ER/IR values in the overall group were 0.89 (SD 0.18) and 0.94 (SD 0.22) for the affected and unaffected shoulders, respectively. The ratio was 0.87 (SD 0.23) in patients with subdeltoid bursitis, 0.88 (SD 0.16) in rotator cuff tendinopathy and 0.87 (SD 0.22) in patients with rotator cuff tears.

Conclusions

The ER/IR ratio appears to be similar between the affected and unaffected shoulders of subjects with nontraumatic cuff pathologies.

Shoulder muscle imbalance as a risk factor for shoulder injury in elite badminton players: A prospective study

OBJECTIVES

To assess the impact of preseason shoulder testing on the risk of significant shoulder injury (SSI) in elite badminton players.

DESIGN

Prospective cohort study.

SETTING

Secondary care, academic medical center.

PARTICIPANTS

Nineteen elite badminton players (19.37 ± 4.79 years, n = 13 males).

MAIN OUTCOME MEASURES

At preseason, they had shoulder examination tests including the table-to-acromion distance and the glenohumeral rotation range of motion. The glenohumeral internal rotation deficit (GIRD) was calculated. Isokinetic internal and external rotator shoulder muscle strength was tested at 60°/s (concentric and eccentric modes) and 240°/s (concentric mode). Bilateral strength ratio (non-dominant:dominant) and unilateral agonist:antagonist conventional and functional ratios (FR: eccentric-to-concentric) were calculated.

RESULTS

During the follow-up time of 38 weeks, SSIs were assessed by an experienced sport physician and 42% of the participants sustained at least one SSI at their dominant side. The preseason GIRD and FR at 240°/s (FR₂₄₀) were independently associated with SSIs (G² = 6.28, p = .012 and G² = 6.23, p = .013, respectively). FR₂₄₀ < 0.69 (odds ratio = 28.0) and GIRD> 14° (odds ratio = 36.14) were predictors for SSIs.

CONCLUSIONS

Lower functional deceleration ratio and greater GIRD are associated with a higher risk of SSI at the dominant side in elite badminton players.

Are Previous Joint Injuries Associated with Muscle Performance in Volleyball Athletes? *

Objective  The aim of the present study is to determine whether previous shoulder and knee injuries were associated with isokinetic fatigue index and agonist/antagonist ratio of shoulder internal/external rotators and knee flexors/extensors in male volleyball athletes.

Methods  The current study is a cross-sectional investigation of 49 male elite volleyball players competing at a high level in Brazil. Isokinetic fatigue index and agonist/antagonist profiles were assessed during the preseason. Additionally, in order to record previous injuries, the athletes answered a standardized questionnaire. We conducted a receiver operating characteristic (ROC) curve analysis to determine the association strength and the clinically relevant cut-off point for variables presenting statistical significance for the area under the curve (AUC) (α = 0.05). An independent t-test was used to compare isokinetic variables between athletes with and without previous injury (α = 0.05).

Results  The results of the ROC curve analysis indicated that hamstring fatigue index values at 300 ^o /s were associated with the presence of previous knee injury (area under the curve [AUC] = 73%, p  = 0.004), and shoulder external rotators fatigue index values at 360°/s were not associated with the presence of previous shoulder injury (AUC = 68%, p  = 0.053).

Conclusions  Elite volleyball athletes who reported previous knee injuries were prone to a higher fatigue index than those reporting no injuries. Knee flexor resistance training might be useful for those athletes who reported knee injuries in the previous season.

Investigating The Association Between Supraspinatus Tendon Abnormality, Shoulder Pain and Isokinetic Strength in Elite Swimmers: A Cross-Sectional Study

Shoulder pain is common among elite swimmers due to the tremendous stress over shoulders during swimming. Supraspinatus muscle is one of the major prime movers and stabilizers of shoulder and is highly susceptible to overloading and tendinopathy. An understanding of the relationship between supraspinatus tendon and pain; and between supraspinatus tendon and strength would assist health care practitioners for developing training regime. The objectives of this study are to evaluate 1) the association between structural abnormality of supraspinatus tendon and shoulder pain and 2) the association between structural abnormality of supraspinatus tendon and shoulder strength. We hypothesized that structural abnormality of supraspinatus tendons positively associated with shoulder pain and negatively associated with shoulder muscle strength among elite swimmers. 44 elite swimmers were recruited from the Hong Kong China Swimming Association. Supraspinatus tendon condition was evaluated using diagnostic ultrasound imaging and shoulder internal and external rotation strength was evaluated by the isokinetic dynamometer. Pearson's R was used to study the correlation between shoulder pain and supraspinatus tendon condition and to evaluate the association between isokinetic strength of shoulders and supraspinatus tendon condition. 82 shoulders had supraspinatus tendinopathy or tendon tear (93.18%). However, there was no statistically significant association between structural abnormality of supraspinatus tendon and shoulder pain. The results showed that there was no association between supraspinatus tendon abnormality and shoulder pain and there was a significant correlation between left maximal supraspinatus tendon thickness (LMSTT) and left external rotation/ concentric (LER/Con) and left external rotation/ eccentric (LER/Ecc) shoulder strength (p < 0.05) while internal rotation/ external rotation (IR/ER) ratio can also be a significant predicator on LMSTT >6mm (R² = 0.462, F = 7.016, df = 1, p = 0.038). Structural change of supraspinatus tendon was not associated with shoulder pain, but could be a predictor on MSTT >6mm in elite swimmers.

Shoulder Internal Rotator Strength as Risk Factor for Shoulder Pain in Volleyball Players

The aim of this study was to identify the intrinsic factors that could increase risk of shoulder pain in adolescent volleyball players. Twenty-eight young male volleyball players (between 14 and 18 years old) participated in this study. Athletes were submitted to: isokinetic muscle strength assessment of shoulder rotator muscles, ball service speed assessment, anterior and posterior drawer test, apprehension test, groove sign and scapular dyskinesia test. Athletes were followed for 16 weeks to monitor the presence of shoulder pain. All athletes were submitted to the same training protocol. During the 16 weeks, 28.5% of the athletes (n=8) experienced shoulder pain in the dominant limb higher than 3 according to Numerical Rating Scale criteria; 71.5% of the athletes (n=20) did not experience pain, or pain equal or lower than 3. The main result of our study was that the odds of feeling pain higher than 3 was significantly higher among players who presented higher values for internal rotation peak torque (OR=1.113, CI 95%=1.006 to 1.232 and p=0.038). The odds of feeling pain increased by 11% for every N·m of the internal rotator muscles. Pre-season isokinetic rotator strength assessments can help identify adolescent volleyball players at increased risk of a shoulder injury.

Prevalence of Glenohumeral Internal Rotation Deficit and Sex Differences in Range of Motion of Adolescent Volleyball Players: A Case-Control Study

Shoulder range of motion (ROM) adaptation is common observed among volleyball players, but studies on the shoulder joint function of adolescent athletes are lacking. This study aimed to clarify the prevalence of glenohumeral internal rotation deficit (GIRD) among adolescent players and differences in ROM based on sex. A questionnaire survey and ROM measurements of the shoulder joint and trunk using a plastic goniometer were conducted on 123 volleyball players (63 males and 60 females; mean age, 15.8 years). The prevalence of GIRD was investigated for internal rotation differences of >10° and total rotation motion of <5°. Questionnaire items and ROM were compared between GIRD and non-GIRD patients, and sex differences in ROM were also presented. Of the participants, 38.2% (n = 47/123) had GIRD. The GIRD group showed a decrease in external rotation on the dominant side (p = 0.003, 1 − beta = 0.84), but this was not associated with a history of shoulder injury. Sex differences in shoulder ROM showed hypomobility in males and hypermobility in females. However, there was no association between shoulder injury and GIRD among adolescent players. There are sex differences in ROM, which should be considered in future studies.

Muscle Quality and Functional and Conventional Ratios of Trunk Strength in Young Healthy Subjects: A Pilot Study

BACKGROUND

The trunk strength conventional ratio (CR) has been evaluated. However, the functional ratio and the ratio of strength to body weight (BW) or muscle mass (MM) have been poorly explored. Relative strength is a measure of muscle quality.

OBJECTIVES

To analyze the trunk strength ratio normalized by BW and MM and compare the trunk's conventional and functional ratios collected in isokinetic and isometric conditions.

METHODS

Twenty-seven healthy males (21.48 ± 2.08 years, 70.22 ± 7.65 kg) were evaluated for trunk isometric and isokinetic strength using a functional electromechanical dynamometer.

RESULTS

The extensor's strength was greater than the flexors, with a CR of 0.41 ± 0.10 to 0.44 ± 0.10. Muscle quality was higher in eccentric contraction and high velocity for flexors and extensors. The functional flexor ratio (FFR) ranged between 0.41 ± 0.09 and 0.92 ± 0.27. The functional extensor ratio (FER) ranged between 2.53 ± 0.65 and 4.92 ± 1.26. The FFR and FER showed significant differences between velocities when considering the peak strength (p = 0.001) and mean strength (p = 0.001).

CONCLUSIONS

Trunk extensors were stronger than the flexors; thus, the CR was less than one. Muscle quality was higher at a high velocity. Unlike CR, FFR and FER behaved differently at distinct velocities. This finding highlights the need to explore the behavior of the functional ratio in different populations.

Clinical Outcomes of Revision Arthroscopic Capsulolabral Repair for Recurrent Anterior Shoulder Instability With Moderate Glenoid Bone Defects: A Comparison With Primary Surgery

Background:

The optimal revision surgery for failed primary arthroscopic capsulolabral repair (ACR) has yet to be determined. Revision ACR has shown promising results.

Purpose:

To compare the functional, strength, and radiological outcomes of revision ACR and primary ACR for anterior shoulder instability.

Study Design:

Cohort study; Level of evidence, 3.

Methods:

Between March 2007 and April 2017, a total of 85 patients underwent ACR (revision: n = 23; primary: n = 62). Functional outcome scores and positive apprehension signs were evaluated preoperatively, at 1 year, and then annually. Isokinetic internal and external rotation strengths were evaluated preoperatively and at 1 year after surgery.

Results:

The mean follow-up was 36.5 ± 10.2 months (range, 24-105 months). There was no significant difference between the revision and primary groups in the glenoid bone defect size at the time of surgery (17.3% ± 4.8% vs 15.4% ± 5.1%, respectively; P = .197). At the final follow-up, no significant differences were found in the American Shoulder and Elbow Surgeons score (97.6 ± 3.1 vs 98.0 ± 6.2, respectively; P = .573), Western Ontario Shoulder Instability Index score (636.7 ± 278.1 vs 551.1 ± 305.4, respectively; P = .584), or patients with a positive apprehension sign (17.4% [4/23] vs 11.3% [7/62], respectively; P = .479) between the revision and primary groups. There was no significant difference between the revision and primary groups for returning to sports at the same preoperative level (65.2% vs 80.6%, respectively; P = .136) and anatomic healing failure at 1 year after surgery (13.0% vs 3.2%, respectively; P = .120). Both groups recovered external rotation strength at 1 year after surgery (vs before surgery), although the strength was weaker than in the uninvolved shoulder. In the revision group, a larger glenoid bone defect was significantly related to a positive apprehension sign (22.0% ± 3.8%) vs a negative apprehension sign (16.0% ± 3.2%; cutoff = 20.5%; P = .003).

Conclusion:

In patients with moderate glenoid bone defect sizes (10%-25%), clinical outcomes after revision ACR were comparable to those after primary ACR. However, significant glenoid bone loss was related to a positive remaining apprehension sign in the revision group. Surgeons should consider these findings when selecting their revision strategy for patients with failed anterior shoulder stabilization.

Can the history of injury influence shoulder isokinetic torque parameters in volleyball players?

The aim of the present study was to compare shoulder internal rotator and external rotator isokinetic parameters in concentric and eccentric contractions between volleyball players with and without a history of shoulder injury. Thirty male volleyball players participated of this study, divided into two groups: with a history of injury (WHI) in the dominant shoulder (11 athletes; age: 19.4 ± 3.6 years) and no history of injury (NHI) (19 athletes; age: 18.3 ± 2.9 years). The peak torque (PT) and concentric (Con) and eccentric (Ecc) PT angles in internal (IR) and external rotation (ER) at velocities of 60 and 180°/s were measured. The conventional (Con_ER:Con_IR), functional spiking (Ecc_ER:Con_IR), and cocking ratios (Ecc_IR:Con_ER) were calculated. No significant differences were found between groups for PT and PT angle, or for conventional, functional spiking, and cocking ratios. However, the spiking ratio was considered low (0.87) in the WHI group. Moreover, for the spiking ratio in the WHI group, PT at 60°/s occurred at different angles. We conclude that previous injury in shoulder did not affect the peak torque, as well as conventional, spiking or cocking ratio. However, the PT angles at 60°/s used to calculate the spiking ratio shifted due the prior injury.

The Relationship between Scapular Upward Rotation and Shoulder Internal and External Rotation Isokinetic Strength in Professional Baseball Pitchers

This study aims to assess the relationship between scapular upward rotation (SUR) across varying humeral-elevation angles (HEAs) and shoulder isokinetic strength and ratio in professional baseball pitchers. The subjects were professional baseball pitchers (n = 16) without a history of shoulder injury in the last six months. The subject’s SUR angles were measured with the humerus elevated at HEAs of 0° (at rest), 60°, 90°, and 120° to the scapular plane. Shoulder isokinetic strength was evaluated for shoulder internal rotation (IR) and external rotation (ER) strength (PT%BW and TW%BW), and the ER/IR strength ratios were determined at 60, 120 and 180°/s using an isokinetic dynamometer. The SUR angle at an HEA of 0° was positively correlated with IR strength at 120°/s (r = 0.535) and 180°/s (r = 0.522). The SUR angle at an HEA of 60° was negatively correlated with the ER/IR strength ratios at 60°/s (r = −0.505) and 120°/s (r = −0.500). The SUR angle at an HEA of 90° was negatively correlated with the ER/IR strength ratios at 60°/s (r = −0.574; r = −0.554) and 120°/s (r = −0.521; r = −0.589) as well as with ER strength at 180°/s (r = −0.591, r = −0.556). The SUR angle at an HEA of 120° was negatively correlated with ER strength at 60°/s (r = −0.558), 120°/s (r = −0.504; r = −0.524), and 180°/s (r = −0.543) and the ER/IR strength ratio at 60°/s (r = −0.517). In this study, we found that the ratio of isokinetic strength between ER and IR became closer to the normal range on increasing the SUR angle. In particular, an HEA of 90°, which resembles the pitching motion, showed a clear relationship between SUR, shoulder ER, and the ratio of ER/IR isokinetic strength in professional baseball pitchers.

Preseason shoulder rotational isokinetic strength and shoulder injuries in volleyball players

BACKGROUND: Rotator cuff weakness is considered an important risk factor for shoulder injuries in volleyball. OBJECTIVE: To evaluate association of shoulder preseason strength status with shoulder injury occurrence in subsequent season. METHODS: Volleyball players (N= 181; 99 men) from Slovenian 1st and 2nd national league volunteered to participate in this prospective cohort study. Preseason isokinetic testing of the shoulder was conducted at 60∘/s in the concentric mode of contraction over a RoM of 60∘ with five repetitions of internal (IR) and external (ER) rotation. During the subsequent season the players reported shoulders injuries through a weekly questionnaire. RESULTS: During the season we have registered 14 (7.7%) shoulder injuries (10 in men). All injuries affected the dominant shoulder. There was significant preseason weakness of ER and lower ER/IR strength ratio in players with shoulder injury. Normal strength ratio ER/IR was a significant protective factor (Exp (B) = 0.217, 95% C.I. 0.058–0.811) for shoulder injury occurrence when controlled for sex and previous injury. CONCLUSIONS: The inclusion of systematic strengthening of the external rotators of the shoulder is necessary, especially for male volleyball players, as part of preventive measures for the prevention of shoulder injuries.

Preseason Upper Extremity Range of Motion and Strength in Relation to In-Season Injuries in NCAA Division I Gymnasts

Background

Gymnastics is a demanding sport that places unique forces on the upper extremity. The repetitive nature of the sport and the high-impact forces involved may predispose the gymnast to overuse injuries. Risk factors for injuries in gymnastics are not well understood.

Purpose/Hypothesis

The purpose of this study was to ascertain whether preseason upper extremity range of motion (ROM) and strength differ between National Collegiate Athletic Association (NCAA) Division I collegiate gymnasts who sustain an in-season upper extremity injury and those who do not. We hypothesized that gymnasts who sustain an upper extremity injury would demonstrate reduced ROM and strength compared with noninjured gymnasts.

Study Design

Cohort study; Level of evidence, 3.

Methods

Over 4 seasons, from 2014 to 2018, a total of 15 female NCAA Division I collegiate gymnasts underwent preseason upper extremity ROM (shoulder: flexion, internal and external rotation; elbow: extension; wrist: extension) and strength (shoulder: internal and external rotation, and middle and lower trapezius) testing. Overuse upper extremity injuries were tracked in each subsequent season. Gymnasts were dichotomized into injured and noninjured groups, and a 2 × 2 analysis of variance was used to measure differences in preseason measures between the groups as well as within arms (injured vs noninjured arm for the injured group; dominant vs nondominant arm for the noninjured group).

Results

A total of 12 overuse upper extremity injuries (10 shoulders; 2 wrist/forearm) occurred during 31 gymnast-seasons. There were no significant interactions for preseason ROM and strength measurements between groups (injured vs noninjured) or within arms (injured and noninjured arm for the injured group; dominant and nondominant arm for the noninjured group; P = .07).

Conclusion

Preseason upper extremity ROM and strength were not different between gymnasts who sustained an in-season upper extremity overuse injury and those who did not. It is possible that ROM and strength measures used to screen other overhead athletes may not capture the unique features and requirements of gymnastics. Further, it may be challenging to discern differences in clinical measures of ROM and strength in gymnastics populations owing to the bilateral nature of the sport.

Changes in Shoulder Rotator Strength After Arthroscopic Capsulolabral Reconstruction in Patients With Anterior Shoulder Instability

Background:

The correlation between isokinetic internal and external rotation (IR and ER) strength and functional outcomes in patients with anterior shoulder instability treated by arthroscopic capsulolabral reconstruction (ACR) has not been studied.

Purpose:

To analyze isokinetic IR and ER strength and their correlation with clinical outcomes in patients with anterior shoulder instability treated by ACR.

Study Design:

Case series; Level of evidence, 4.

Methods:

Between January 2004 and June 2015, a total of 104 patients who underwent ACR for anterior shoulder instability were analyzed. The mean peak torque (PT) in IR (IR_PT) and ER (ER_PT), PT deficit (PTD; %) relative to the opposite healthy shoulder, and PT ratio (PTR; ER_PT/IR_PT) were calculated before and 1 year after surgery. Functional scores were evaluated before surgery and at every follow-up visit. Recurrence and postoperative apprehension during ER at 90° of arm abduction were evaluated at 1 year and the final follow-up (76.6 ± 64.4 months).

Results:

IR and ER strength were measured for 68 of 104 patients at 1 year after surgery. ER_PT and IR_PT were less on the involved side than on the uninvolved side before surgery (0.29 ± 0.10 vs 0.33 ± 0.10 N·m/kg, respectively, for ER_PT [P = .002]; 0.36 ± 0.14 vs 0.41 ± 0.16 N·m/kg, respectively; for IR_PT [P = .01]). At 1 year after surgery, IR_PT on the involved side recovered (0.40 ± 0.20 N·m/kg), whereas ER_PT remained weak (0.30 ± 0.13 N·m/kg) relative to the baseline value. PTD in IR (PTD_IR) improved to 2.2% ± 24.4% (P = .012), whereas PTD in ER (PTD_ER) showed no improvement (13.5% ± 13.8%; P = .569). PTR on the involved side improved from 1.07 ± 1.71 to 0.86 ± 0.23 at 1 year (P < .001). All functional scores improved significantly at the final follow-up. At 1 year, 9 of 68 (13.2%) patients showed positive apprehension. PTD_IR and PTD_ER on the involved side were worse in patients with positive apprehension than in those with negative apprehension (P = .039 and .014, respectively). PTD_ER was worse than PTD_IR in patients with positive apprehension at 1 year (P = .022).

Conclusion:

For those with anterior shoulder instability, preoperative IR and ER strength of the involved shoulder were lower than those of the uninvolved shoulder. IR_PT recovered, whereas ER_PT remained weak after ACR. To prevent positive apprehension after surgery, IR and ER strengthening exercises are important, with more emphasis on exercises for ER.

The Effect of Shoulder Injury Prevention Program on Shoulder Isokinetic Strength in Young Male Volleyball Players

The purpose of this study was to examine the effects of an eight-week 11 + S programme on isokinetic shoulder strength in young male volleyball players. Twenty-eight top-level young male volleyball players were recruited for this study. The players were randomly assigned into intervention (14 players) and control (14 players) groups. The intervention group performed the 11 + S as a warm-up before training at least three times a week for eight weeks. Dominant shoulder strength was measured using an isokinetic dynamometer at 60°/s and 180°/s. The functional deceleration ratio (FDR) was calculated as a functional strength profile. 20% FDR improvement after eight weeks of 11 + S at 180°/s (p = 0.003) were observed. No other statistically significant effects for shoulder strength improvement was observed (p > 0.05). Eight weeks of 11 + S warm-up programme improved the glenohumeral muscle imbalance by increasing the functional deceleration ratio (FDR) of shoulder muscles in young male volleyball players.

Reliability of a standing isokinetic shoulder rotators strength test using a functional electromechanical dynamometer: effects of velocity

Background

The evaluation of the force in internal rotation (IR) and external rotation (ER) of the shoulder is commonly used to diagnose possible pathologies or disorders in the glenohumeral joint and to assess patient’s status and progression over time. Currently, there is new technology of multiple joint isokinetic dynamometry that allows to evaluate the strength in the human being. The main purpose of this study was to determine the absolute and relative reliability of concentric and eccentric internal and external shoulder rotators with a functional electromechanical dynamometer (FEMD).

Methods

Thirty-two male individuals (21.46 ±  2.1 years) were examined of concentric and eccentric strength of shoulder internal and external rotation with a FEMD at velocities of 0.3 m s⁻¹ and 0.6 m s⁻¹. Relative reliability was determined by intraclass correlation coefficients (ICC). Absolute reliability was quantified by standard error of measurement (SEM) and coefficient of variation (CV). Systematic differences across velocities testing circumstances, were analyzed with dependent t tests or repeated-measures analysis of variance in case of 2 or more than 2 conditions, respectively.

Results

Reliability was high to excellent for IR and ER on concentric and eccentric strength measurements, regardless of velocity used (ICC: 0.81–0.98, CV: 5.12–8.27% SEM: 4.06–15.04N). Concentric outcomes were more reliable than eccentric due to the possible familiarization of the population with the different stimuli.

Conclusion

All procedures examined showed high to excellent reliability for clinical use. However, a velocity of 0.60 m s⁻¹ should be recommended for asymptomatic male patients because it demands less time for evaluation and patients find it more comfortable.

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

Prospective and cross-sectional studies have used pre-season isokinetic dynamometry strength and endurance measurements of shoulder internal rotation (IR) and external rotation (ER) to determine if they can be correlated to injury. However, to date, no review has provided a synthesis of all available literature on this topic. The aim of this systematic review was to identify isokinetic dynamometry studies that assess shoulder IR and ER strength and endurance in the overhead athletic population in relation to shoulder injury. Electronic databases (PubMed, CINAHL, and SportDiscus) were searched through September 2019 using pre-determined search terms. Both prospective and cross-sectional studies were included in this review. Studies were assessed for quality using either Appraisal Tool for Cross-sectional Studies (AXIS) or Critical Appraisal Skills Programme (CASP). Data on outcome measures of strength and endurance peak torque (PT) and ratios (ER:IR) were extracted and further analysed using a best evidence synthesis approach. A total of 13 articles met the inclusion criteria. Conflicting evidence was found when reviewing all studies without differentiating by study type. Prospective study designs revealed strong evidence that reduced IR endurance and reduced strength ratios are predictive of shoulder injury. Cross-sectional literature showed only conflicting and limited evidence for all outcome measures. At this stage, more research is needed in individual sporting populations using prospective cohort designs.

Which muscle performance can be improved after arthroscopic Bankart repair?

BACKGROUND

There are no published reports available regarding neuromuscular control recovery in nonathletic patients after arthroscopic (A/S) Bankart repair. This study aimed to compare neuromuscular control and performance of the rotator cuff muscles between patients who underwent A/S Bankart repair and normal controls.

METHODS

In total, 32 nonathletic patients who underwent A/S Bankart repair were compared with 32 asymptomatic nonathletic volunteers. Neuromuscular control index (time to peak torque and acceleration time), muscle strength ratio, muscle strength, and muscle endurance of the internal rotators (IRs) and external rotators (ERs) were measured using an isokinetic device at an angular velocity of 180°/s, with 90° shoulder abduction.

RESULTS

The neuromuscular control indices of both IRs and ERs were significantly lower in patients who underwent A/S Bankart repair than in normal controls (time to peak torque, IRs: 1059 ± 143 ms vs. 679 ± 226 ms, P = .011; ERs: 595 ± 286 ms vs. 379 ± 123 ms, P = .044; acceleration time, IRs: 75 ± 16 ms vs. 62 ± 15 ms, P = .039, ERs: 70 ± 19 ms vs. 54 ± 18 ms, P = .047). Muscle endurance was significantly lower in patients who underwent A/S Bankart repair than in normal controls (IRs: 670 ± 1 J vs. 718 ± 2 J, P = .002, ERs: 422 ± 6 J vs. 501 ± 2 J, P = .044). The neuromuscular control index showed a significant negative correlation with muscle endurance for both IRs and ERs after the operation (IRs: r = -0.737, P = .003, ERs: r = -0.617, P = .019).

CONCLUSION

Compared with normal controls, patients who underwent A/S Bankart repair did not show complete recovery of neuromuscular control of IRs and ERs, although their muscle strength ratio and muscle strength had fully recovered.

Isokinetic Fatigue Ratio of Shoulder Rotators in Elite Softball Players With and Without Rotator Cuff Tendinopathy, and its Association With the Subacromial Space

CONTEXT

Fatigue of the shoulder rotators may cause reduction of the subacromial space (SAS) and contribute to rotator cuff tendinopathy.

OBJECTIVES

To compare the isokinetic peak torques and fatigue ratios of shoulder external rotators (ER) and internal rotators (IR) between elite softball athletes with and without rotator cuff tendinopathy and to investigate their associations with the SAS.

DESIGN

Cross-sectional study.

SETTING

University laboratory.

PARTICIPANTS

Twenty-five elite softball players and 31 asymptomatic sedentary controls participated in this study.

MAIN OUTCOME MEASURES

Isokinetic concentric IR and ER peak torque and fatigue ratio were measured at 60°/s and at 180°/s, respectively; and ultrasound measurement of the SAS was measured during 0° and 60° of shoulder abduction.

RESULTS

Athletes with rotator cuff tendinopathy demonstrated lower peak torque in shoulder concentric ER when compared with their healthy counterparts (37.8 [5.8%] vs 43.6 [8.5%]). No significant difference was found in the fatigue ratios of ER, IR, and ER/IR when compared between elite softball athletes with and without rotator cuff tendinopathy (all P > .24). In asymptomatic athletes, greater IR peak torque (r = .583, P = .03), lower ER/IR strength ratio (r = -.605, P = .02), and greater ER/IR fatigue ratio (r = .575, P = .03) were moderately associated with more reduction of the SAS during 0° and 60° of shoulder abduction.

CONCLUSIONS

Decreased strength ratio and fatigue ratio of ER/IR were related to reduction of the SAS.

Tight shoulders: A clinical, kinematic and strength comparison of symptomatic and asymptomatic male overhead athletes before and after stretching

A tightness of the posterior structures of the throwing shoulder has been hypothesised to be associated with injuries and pain because of alterations of the scapular kinematics and muscular imbalances. The aims of this study were to identify the clinical and biomechanical profile of symptomatic and asymptomatic overhead athletes with a tight shoulder and to evaluate the efficiency of a self-applied stretching program. Twenty male overhead athletes were recruited. Half of them reported a painful shoulder at the beginning of the study. For four weeks, the volunteers performed daily stretching exercises. Before and after the stretching program, gleno-humeral mobility, scapular kinematics, rotator muscles strength and pain were evaluated. Before stretching, the main difference between the groups was more impingement syndrome and rotator cuff tendon lesion positive tests in the symptomatic group (p < 0.027, effect size = 0.51). After the program, pain reported by the symptomatic volunteers was reduced by approximately 40% and the gleno-humeral internal rotation bilateral difference was significantly reduced by 77.6% (p < 0.009, effect size = 0.84). In the symptomatic group, the scapula at rest was significantly more posteriorly tilted (p = 0.027, effect size = 0.69) after the stretching; a position that has been shown to limit the risk of impingement. The absence of significant differences of the profiles of the symptomatic and asymptomatic overhead athletes before stretching may indicate that the initiation of early prevention programs, including self-applied stretching, should not rely solely on biomechanical and clinical parameters and might be recommended to all players with a tight shoulder.

Influence of Shoulder Position on Functional Control Ratio During Isokinetic Assessment

CONTEXT

One of the possible mechanisms leading to secondary impingement syndrome may be the strength imbalance of shoulder rotators which is known as functional control ratio (FCR). The FCR is a ratio dividing the eccentric peak torque of the external rotators by the concentric peak torque of the internal rotators. Previous studies have focused on the reproducibility and reliability of isokinetic assessment, but there is little information on the influence of variable shoulder positions on FCR.

OBJECTIVE

To compare shoulder FCR across 3 different shoulder abduction positions during isokinetic assessment.

DESIGN

Cross-sectional study.

SETTING

Biomechanics laboratory.

PARTICIPANTS

Thirty-one healthy young university students (age 22.35 [0.95] y, weight 60.52 [9.31] kg, height 168.23 [9.47] cm).

INTERVENTIONS

The concentric peak torque of internal rotators and eccentric peak torque of external rotators of right shoulder were measured on an isokinetic dynamometer.

MAIN OUTCOME MEASURES

Concentric peak torque of the internal rotators and eccentric peak torque of the external rotators, measured using an isokinetic dynamometer.

RESULTS

The concentric peak torque of internal rotators was significantly lower at 120° shoulder abduction compared with other positions (P < .001). The FCR was significantly higher at 120° shoulder abduction than 90° (P = .002) or 60° (P < .001) shoulder abduction because of the lower concentric peak torque. No significant difference was found in the FCR between the other 2 shoulder positions (P = .14).

CONCLUSIONS

Shoulder position variations may influence FCR because of weakness of the internal rotators. Rehabilitation and injury prevention training programs should specifically focus on strengthening the internal rotators at more elevated angles of shoulder abduction.

Isokinetic Performance of Shoulder External and Internal Rotators of Professional Volleyball Athletes by Different Positions

This study aimed to exam the isokinetic shoulder rotator strength of professional volleyball athletes, by playing positions. This cross-sectional study included a total of 49 healthy male professional volleyball players. We measured the isokinetic strength of the external rotator (ER) and internal rotator (IR) muscles and compared the dominant and non-dominant shoulders at angular speeds of 60°/s and 180°/s. In ER, all positions of players had similar strength between the dominant shoulder and non-dominant shoulders. Conversely, all playing positions except libero had stronger strength in dominant shoulder than that in the non-dominant shoulder. The ER/IR ratio in the dominant shoulder was significantly lower only for the attacker (outside hitter and opposite) at 60°/s and 180°/s (P < 0.0001; P = 0.0028 respectively) and blocker at 60°/s (P = 0.0273) when compared with non-dominant shoulder. Furthermore, the attacker had a lower ER/IR ratio in the dominant shoulder than setter and libero at 60°/s and 180°/s. For elite volleyball players without injury, the dominant shoulder had a higher strength of internal rotation, causing the relative muscle imbalance than the non-dominant shoulder, especially for the attacker and blocker positions. Training program should be individualized for each playing position to improve the imbalanced shoulder.

Comparison of shoulder range of motion, strength, and upper quarter dynamic balance between NCAA division I overhead athletes with and without a history of shoulder injury

OBJECTIVE

To determine differences in shoulder range of motion, strength, and upper quarter dynamic balance between collegiate overhead athletes with and without a history of a shoulder injury.

DESIGN

Cross-sectional study.

SETTING

Athletic training clinic.

PARTICIPANTS

58 overhead athletes who were fully participating in NCAA Division I overhead sports (baseball, softball, volleyball, and tennis) and free of any current shoulder injury were included. Participants were divided into a shoulder injury history group (n = 25) and uninjured group (n = 33). Participants in the shoulder injury history group had a previously resolved shoulder injury.

MAIN OUTCOME MEASURES

Active range of motion assessments for shoulder internal rotation, external rotation, and horizontal adduction. Isometric strength assessments for shoulder IR and ER. The Upper Quarter Y-Balance Test.

RESULTS

The shoulder injury history group demonstrated a lower Upper Quarter Y-Balance Test mean score in the superolateral direction (p = .03, d = 0.56), but no group differences existed for other results (p > .05).

CONCLUSIONS

Overhead athletes with a history of shoulder injury had worse upper quarter dynamic balance versus those without the history. From a clinical perspective, the findings may have significant implications for developing shoulder re-injury prevention and rehabilitation protocols in relation to their shoulder injury history.

Effects of medicine ball mass on the intensity of 90°/90° plyometric throwing exercise

OBJECTIVES

To quantify the effects of medicine ball mass (1 kg, 1.5 kg, 2 kg) on the intensity of 90°/90° plyometric throwing exercise.

STUDY DESIGN

Controlled laboratory study.

SETTING

Biomechanics laboratory.

PARTICIPANTS

Fifteen physically active collegiate aged men.

MAIN OUTCOME MEASURES

Kinematics of the upper extremity were collected during completion of eight to ten repetitions of 90°/90° plyometric throwing exercise with three different mass medicine balls. Four parameters, medicine ball release and contact momentum, time-to-rebound, and contact time, were computed for each selected repetition and used for statistical analysis.

RESULTS

Ball mass did not significantly influence time-to-rebound (P = .718) and had a small (less than 0.05s) effect on ball contact time (P = .039). Ball release momentum was significantly greater (P < .001, 67-123% greater) than ball contact momentum. Medicine ball mass significantly increased both ball release (34-35%) and ball contact (45-67%) momentum however the effect was significantly greater for ball release momentum (P = .005).

CONCLUSIONS

These results document the effects of increasing medicine ball mass during 90°/90° plyometric throwing exercise and provide evidence for designing upper extremity plyometric training programs. Based on ball contact momentum being less than ball release momentum, as well as ball mass having greater influence on ball release velocity, we suggest that 90°/90° plyometric throwing exercise is a safe exercise.

Profiling Isokinetic Strength of Shoulder Rotator Muscles in Adolescent Asymptomatic Male Volleyball Players

The aim of the study was to describe the strength symmetry of internal and external rotator muscles and the conventional and functional strength balance ratios between these muscles in adolescent male volleyball players. Twenty-eight male adolescent volleyball players (15.5 ± 1.1 years (15–17 years); 73.2 ± 10.9 kg (55.3–100.1 kg) and 184.9 ± 8.4 cm (170–209 cm)) participated in this cross-sectional study. Concentric and eccentric peak torque of external and internal rotator muscles were measured, and conventional and functional strength balance ratios were calculated. The dominant limb presented significantly higher values for peak torque than the non-dominant limb of internal rotator muscles at concentric action assessed at 60°/s (48.7 ± 13.7 Nm and 43.9 ± 11.6 Nm, p = 0.01 and d value = 0.37) and at 240°/s (44.7 ± 11.2 Nm and 41.1 ± 11.0 Nm, p = 0.03 and d = 0.32). However, there was no difference in the peak torque of external rotator muscle between limbs for either angular speed. Regarding strength balance ratios, neither conventional (74.8 ± 14.3 for dominant limb and 80.1 ± 14.0 for non-dominant limb, p = 0.06 and d = 0.37) nor functional ratio (1.2 ± 0.4 for dominant limb and 1.3 ± 0.5 for non-dominant limb, p = 0.06 and d = 0.22) presented significant contralateral differences. Despite the short practice time, adolescent male volleyball athletes already have significant contralateral differences for internal rotator muscles and conventional ratio tends to be asymmetrical. Thus, preventive shoulder-strengthening programs, focused on the internal rotator muscles of the non-dominant limb, aiming to correct contralateral deficiency and conventional ratio, may be warranted for this population in the process of biological growth, maturation and development.

Strength Reduction in Unilateral Shoulder Pain: Is the Healthy Side Really Healthy in Rotator Cuff Disease?

OBJECTIVE

The primary aim was to ascertain whether unilateral shoulder pain is implicated in strength reduction both on the ipsilateral and contralateral side. Secondarily, we aimed to determine whether strength was affected by sonographic tendon abnormalities.

DESIGN

A total of 122 subjects were evaluated. Sixty-six female subjects with unilateral shoulder pain in the dominant arm were recruited. Abduction strength was measured in both the dominant and nondominant arm. High-resolution ultrasonography was also conducted on both shoulders. A match-paired control group (n = 66) composed of healthy volunteers underwent the same strength and sonography tests. Subjects with any radiographic anomaly were excluded from the control group. A mixed analysis of variance was performed to test the effect of unilateral shoulder pain on abduction strength. The effect of tendinopathy on shoulder strength was investigated using a mixed 2 × 2 analysis of variance.

RESULTS

Analysis of variance showed that patients with dominant shoulder pain had lower shoulder strength (11.65 ± 4.05 kg) when compared with controls (14.37 ± 4.00 kg; F = 10.454, P = 0.002). No statistically significant effects were found when comparing subjects with and without tendinopathy among the study group.

CONCLUSIONS

In patients with unilateral shoulder pain, abduction strength was found to be lower both on the ipsilateral and contralateral side. The presence of tendinopathy did not affect the reduction in strength. Future research is needed to substantiate these findings.

Spiking Kinematics in Volleyball Players With Shoulder Pain

CONTEXT

Spiking is one of the most frequently used scoring techniques in volleyball games, and around 80% of shoulder pain in volleyball players is linked with the spiking movement.

OBJECTIVE

To investigate the differences in glenohumeral joint, scapular, and trunk movements during the spiking motion between volleyball players with and those without shoulder pain.

DESIGN

Cross-sectional study.

SETTING

University laboratory.

PATIENTS OR OTHER PARTICIPANTS

Twenty amateur volleyball players with shoulder pain (age = 21.8 ± 1.79 years, with an average of 4.0 ± 0.92 years of volleyball experience and 6.0 ± 3.51 months of shoulder pain) and 20 sex-, age-, and experience-matched control participants.

MAIN OUTCOME MEASURE(S)

The 3-dimensional kinematics of the shoulder joint, scapula, and trunk during spiking were assessed using an electromagnetic tracking system.

RESULTS

Compared with the control group, individuals with shoulder pain demonstrated less scapular posterior tilt ( P = .041) and more glenohumeral horizontal abduction ( P = .008) and scapular internal rotation ( P = .02) at ball contact when performing the cross-body spike.

CONCLUSIONS

The decrease in scapular posterior tilt, along with increased glenohumeral horizontal abduction and scapular internal rotation, was associated with shoulder pain in university volleyball players. These changes should be addressed in the training and treatment of young volleyball players.

Isokinetic assessment of shoulder complex strength in adolescent elite synchronized swimmers

Children and adolescent participation in sport has increased in recent years. Synchronized swimming requires correct muscle balance in the shoulder complex. The purpose of this study was to establish isokinetic strength profiles and peak torque ratios of shoulder internal and external rotator muscles in a female high-level synchronized swimming team. Twenty-six adolescent female high-level synchronized swimmers, aged 12-14, participated in this study. Maximal bilateral shoulder concentric external and internal rotation force was measured at 60°/s (5 repetitions) and 180°/s (15 repetitions). The isokinetic concentric strength generated by the internal rotator muscles was significantly higher (p < 0.05) than by the external rotators in both limbs and at both velocities. Significant bilateral differences in the external rotation (ER):internal rotation (IR) strength ratio were noted at 60°/s. Isokinetic assessment is essential in sports medicine, since it is the only test capable of diagnosing any shoulder strength deficit.

Profiling the Isokinetic Muscle Strength of Athletes Involved in Sports Characterized by Constantly Varied Functional Movements Performed at High Intensity: A Cross-Sectional Study

BACKGROUND

Constantly varied functional movements performed at high intensity (FMHI) is a type of strength and general conditioning program that has gained widespread popularity in recent years. The very intense exercises performed with lower and upper limbs may create muscular asymmetry or imbalance between agonist and antagonist muscles, and therefore the characterization of isokinetic muscle strength, side-to-side difference, and balance ratios for lower and upper limbs may contribute to a better understanding of the modality characteristics.

OBJECTIVE

To evaluate the knee and shoulder strength of FMHI athletes of both sexes.

DESIGN

Cross-sectional study.

SETTING

Exercise physiology laboratory.

PARTICIPANTS

Sixty FMHI athletes (30 M/30 W) with more than 2 years' experience.

METHODS

Athletes performed isokinetic tests in both lower and upper limbs: concentrically at 60°/s and 240°/s and eccentrically at 240°/s.

MAIN OUTCOME MEASUREMENTS

Isokinetic peak torque of knee flexor and extensor and shoulder internal and external rotator muscles. Conventional and functional strength balance ratios and side-to-side strength difference.

RESULTS

Concentric peak torque values relative to total body mass for shoulder and knee joints were higher in men than women on both sides. Eccentric peak torque values for knee flexor-dominant and extensor-nondominant limbs showed no difference between the sexes. The knee conventional strength balance ratio for dominant and nondominant sides in women (51.5% ± 7.0% and 51.0% ± 7.1%, respectively) and for dominant and nondominant sides in men (54.4% ± 15.2% and 51.5% ± 9.9%, respectively) were no different between the sexes or limbs. The shoulder conventional strength balance ratio was higher in women (78.1 ± 13.2%) than in men (67.6% ± 10.9%) on the nondominant side. Knee and shoulder functional strength balance ratios in nondominant limbs were higher for women than men. Both sexes presented no side-to-side difference for knee joints or muscles, or for shoulder IR muscles, but ER was stronger in dominant limbs.

CONCLUSIONS

These data from highly trained FMHI athletes can be compared to that of other athletes to help determine individual weaknesses, strengths, and imbalances, and may be useful for designing training programs.

LEVEL OF EVIDENCE

III.

Significantly Increased Odds of Reporting Previous Shoulder Injuries in Female Marines Based on Larger Magnitude Shoulder Rotator Bilateral Strength Differences

Background:

Musculoskeletal injuries to the extremities are a primary concern for the United States (US) military. One possible injury risk factor in this population is side-to-side strength imbalance.

Purpose:

To examine the odds of reporting a previous shoulder injury in US Marine Corps Ground Combat Element Integrated Task Force volunteers based on side-to-side strength differences in isokinetic shoulder strength.

Study Design:

Cohort study; Level of evidence, 3.

Methods:

Male (n = 219) and female (n = 91) Marines were included in this analysis. Peak torque values from 5 shoulder internal/external rotation repetitions were averaged and normalized to body weight. The difference in side-to-side strength measurements was calculated as the absolute value of the limb difference divided by the mean peak torque of the dominant limb. Participants were placed into groups based on the magnitude of these differences: <10%, 10% to 20%, and >20%. Odds ratios (ORs) and 95% CIs were calculated.

Results:

When separated by sex, 13.2% of men reported an injury, while 5.5% of women reported an injury. Female Marines with >20% internal rotation side-to-side strength differences demonstrated increased odds of reporting a previous shoulder injury compared with female Marines with <10% strength differences (OR, 15.4; 95% CI, 1.4-167.2; P = .03 ) and female Marines with 10% to 20% strength differences (OR, 13.9; 95% CI, 1.3-151.2; P = .04). No significant ORs were demonstrated in male Marines.

Conclusion:

Marines with larger magnitude internal rotation strength differences demonstrated increased odds of reporting a previous shoulder injury compared with those with lesser magnitude differences. Additionally, female sex appears to drastically affect the increased odds of reporting shoulder injuries (OR, 13.9-15.4) with larger magnitude differences (ie, >20%) compared with those with lesser magnitude differences (ie, <10% and 10%-20%). The retrospective cohort design of this study cannot delineate cause and effect but establishes a relationship between female Marines and greater odds of larger magnitude strength differences after returning from an injury.

Shoulder Dynamic Control Ratio and Rotation Range of Motion in Female Junior Elite Handball Players and Controls

OBJECTIVE

To compare glenohumeral range of motion and shoulder rotator muscle strength in healthy female junior elite handball players and controls.

DESIGN

Cross-sectional case-control study.

SETTING

Sports medical center.

PARTICIPANTS

Forty elite female handball players and 30 controls active in nonoverhead sports participated in this study.

MAIN OUTCOME MEASURES

Passive external rotator (ER), internal rotator (IR), and total range of motion (TROM) of the dominant and nondominant arm were examined with a goniometer. An isokinetic dynamometer was used to evaluate concentric and eccentric rotator muscle strength at 60 and 120 degrees/s with dynamic control ratio (DCR = ERecc:IRcon) as the main outcome parameter.

RESULTS

Except for the ER range of motion in the nondominant arm, no significant differences were found between groups for IR, ER of the dominant arm, and the TROM. Within the handball group, the side-to-side difference for IR of the dominant arm was -1.4 degrees. The ER and the TROM of the dominant arm were significantly larger, 6.3 and 4.9 degrees, respectively. For both groups, the DCR values were above 1 and no significant differences were found between the dominant and nondominant arm. The DCR values in the handball group were significantly lower than in the control group.

CONCLUSIONS

Based on the adopted definitions for muscle imbalance, glenohumeral internal range of motion deficit and TROM deficit our elite female handball players seem not at risk for shoulder injuries. Prospective studies are needed to support the belief that a DCR below 1 places the shoulder at risk for injury.

The effects of preventive rubber band training on shoulder joint imbalance and throwing performance in handball players: A randomized and prospective study

OBJECTIVES

To investigate the effects of a strength training program (STP) using rubber band exercises.

METHODS

Twenty-five athletes were divided into two groups: muscular imbalance in the dominant (D) and in the non-dominant (ND) upper limbs. Each group was subdivided into experimental and control groups. Experimental groups performed eighteen sessions of STP. Athletes were submitted to ball throwing and isokinetic strength tests to assess the muscular strength of the shoulder rotator muscles and conventional and functional balance ratios.

RESULTS

STP improved external rotator peak torque (18.0 ± 0.8 to 21.3 ± 1.0 Nm, p < 0.01) and total work (29.3 ± 0.9 to 34.5 ± 1.5 J, p < 0.01) in the D experimental group, while only total work (34.8 ± 2.5 to 37.6 ± 3.1 J, p < 0.03) improved in the D control group. The ND experimental group also presented significant improvement in external rotator peak torque (18.8 ± 0.8 to 21.1 ± 1.3 Nm, p < 0.01) and total work values (29.0 ± 1.4 to 34.6 to 1.6 J, p < 0.01) while there was no strength improvement in the ND control group. The ND experimental group showed an improvement in conventional (61.5 ± 3.5 to 72.7 ± 3.0%, p = 0.03) and functional (1.0 ± 0.1 to 1.6 ± 0.08, p < 0.01) ratios. STP did not improve the conventional ratio in the D experimental group. However, STP produced a large effect size. The D experimental group presented an improvement in ball velocity (49.0 ± 2.4 to 52.5 ± 2.2 km/h, p = 0.04) in standing position throwing.

CONCLUSIONS

STP improves muscular strength of external rotator muscles and muscular balance.

Influence of Posture-Cuing Shirt on Tennis Serve Kinematics in Division III Tennis Players

OBJECTIVE

The purpose of this study was to evaluate the influence of a posture-cuing shirt on internal rotation velocity of the shoulder during a tennis swing and to determine this influence on shoulder external rotation position.

METHODS

Nine healthy competitive college tennis players from a Division III college participated in this study. High-speed motion capture allowed for 3-dimensional analysis of shoulder kinematics during a tennis serve. Two conditions were evaluated while the athletes performed a high-velocity tennis serve: a standard tennis shirt and a posture-cuing shirt.

RESULTS

Shoulder internal rotation velocity increased when wearing the posture-cuing shirt. Peak internal rotation velocity increased from 960.61°/s ± 93.24°/s to 1217.96°/s ± 155.01°/s (t = -1.76, P = .058). Internal rotation velocity at the time of impact increased from 765.18°/s ± 95.48°/s to 900.54°/s ± 105.33°/s (t = -1.50, P = .086). Shoulder maximum external rotation did not differ between the 2 conditions, at 172.00° ± 2.92° and 170.89° ± 3.70° (t = 0.325, P = .754).

CONCLUSIONS

Wearing a posture-cuing shirt may possibly alter shoulder kinematics during an overhead sport activity such as tennis. Internal rotation velocity seemed to improve while wearing this shirt, although shoulder external rotation position did not change. It is not known if these improvements can influence injury risk.

Upper Quadrant Field Tests and Isokinetic Upper Limb Strength in Overhead Athletes

CONTEXT

Isokinetic testing is used to determine possible deficits in upper extremity strength in overhead athletes. Given that isokinetic testing is restricted to a laboratory setting, field tests, such as the Seated Medicine Ball Throw (SMBT) and Upper Quarter Y-Balance Test (YBT-UQ), were developed to assess upper body performance. The relationships between these field tests and isokinetic strength have not been examined.

OBJECTIVE

To investigate the relationship between isokinetic strength testing for shoulder external and internal rotation and elbow flexion and extension and SMBT distance and YBT-UQ performance in overhead athletes.

DESIGN

Cross-sectional study.

SETTING

Institutional laboratory.

PATIENTS OR OTHER PARTICIPANTS

A total of 29 healthy overhead athletes (14 men, 15 women; age = 21.6 ± 2.5 years, height = 177.7 ± 9.7 cm, mass = 70.3 ± 11.5 kg).

INTERVENTION(S)

A Biodex dynamometer was used to measure the isokinetic strength of the shoulder and elbow muscles. Upper extremity performance was assessed using the SMBT and YBT-UQ.

MAIN OUTCOME MEASURE(S)

We used Pearson correlation coefficients and coefficients of determination to analyze the relationship between SMBT and YBT-UQ performance and the isokinetic strength variables.

RESULTS

We observed moderate to strong correlations between the SMBT and isokinetic shoulder and elbow strength (r range = 0.595-0.855) but no correlations between the YBT-UQ and isokinetic strength variables. The shared variance between these strength variables and the SMBT ranged from 35.4% to 64.5% for shoulder strength and 58.5% to 73.1% for elbow strength.

CONCLUSIONS

These findings suggested that the SMBT is a reliable, low-cost, and easy- and quick-to-administer alternative to isokinetic testing for evaluating upper extremity strength in a clinical setting. Performance on the YBT-UQ did not seem to be related to upper limb strength and, therefore, cannot be used for this purpose. Using the YBT-UQ for other purposes may have value.

Assessment of isokinetic muscle function in Korea male volleyball athletes

Volleyball players performed numerous repetitions of spike actions, which uses and requires strong and explosive force, and control of the muscles of the shoulder, lower back, and legs. Muscle imbalance is one of the main causes of sport injuries. The purpose of this study was to assess isokinetic muscle functions in male volleyball players. We thus aim to accurately evaluate their muscle functions, and identify the best training strategy to achieve optimal muscle strength balance in future training programs. The participants in this study consisted of 14 male volleyball players. Muscle strength was measured using the isokinetic dynamometer. Muscle strength was evaluated in terms of peak torque and average power, calculated from five repeated measurements at an angular speed of 60°/sec. Three players who were left attackers showed shoulder imbalance, four players showed trunk joint imbalance, nine players had knee joint of extension/flexion imbalance and four players showed left/right imbalance. The results showed that the number of volleyball players with differences between the strength of the bilateral knee muscles, and between the strength of the hamstrings and quadriceps muscles was higher than the number of players with differences between the strength of the shoulder internal and external rotation muscles, and higher than the number of players with differences between the strength of the lower back extension and flexion muscles.

Shoulder-Rotator Strength, Range of Motion, and Acromiohumeral Distance in Asymptomatic Adolescent Volleyball Attackers

CONTEXT

Sport-specific adaptations at the glenohumeral joint could occur in adolescent athletes because they start participating in high-performance sports in early childhood.

OBJECTIVE

To investigate shoulder-rotator strength, internal-rotation (IR) and external-rotation (ER) range of motion (ROM), and acromiohumeral distance (AHD) in asymptomatic adolescent volleyball attackers to determine if they have risk factors for injury.

DESIGN

Cross-sectional study.

SETTING

University laboratory.

PARTICIPANTS

Thirty-nine adolescent high school-aged volleyball attackers (22 boys, 17 girls; age = 16.0 ± 1.4 years, height = 179.2 ± 9.0 cm, mass = 67.1 ± 10.9 kg, body mass index = 20.7 ± 2.6 kg/m²).

MAIN OUTCOME MEASURE(S)

Shoulder IR and ER ROM, total-rotation ROM, glenohumeral IR deficit, AHD, and concentric and eccentric strength of the shoulder internal and external rotators were tested bilaterally.

RESULTS

External-rotation ROM was greater (t₃₈ = 4.92, P < .001), but IR ROM (t₃₈ = -8.61, P < .001) and total ROM (t₃₈ = -3.55, P = .01) were less in the dominant shoulder, and 15 athletes had a glenohumeral IR deficit (IR ROM loss > 18°). We observed greater concentric internal-rotator (t₃₈ = 2.89, P = .006) and eccentric external-rotator (t₃₈ = 2.65, P = .01) strength in the dominant than in the nondominant shoulder. The AHD was less in the dominant shoulder (t₃₈ = -3.60, P < .001).

CONCLUSIONS

Adolescent volleyball attackers demonstrated decreased IR ROM, total ROM, and AHD and increased ER ROM in their dominant shoulder. Therefore, routine screening of adolescent athletes and designing training programs for hazardous adaptive changes could be important in preventing shoulder injuries.

The volleyball athlete's shoulder: biomechanical adaptations and injury associations

In volleyball, the dominant shoulder of the athlete undergoes biomechanical and morphological adaptations; however, definitive conclusions about their exact nature, aetiology, purpose and associations with shoulder injury have not been reached. We present a systematic review of the existing literature describing biomechanical adaptations in the dominant shoulders of volleyball players and factors that may predispose to shoulder pain/injury. A thorough literature search via Medline, EMBASE and SCOPUS was conducted for original studies of volleyball players and 15 eligible articles were identified. Assessment of study quality was performed using the STROBE statement. The reviewed literature supports the existence of a glenohumeral internal rotation deficit (GIRD) and a possible (and less pronounced) external rotation gain in the dominant vs. the non-dominant shoulder of volleyball athletes. Unlike other overhead sports, the GIRD in volleyball athletes appears to be anatomical as a response to the repetitive overhead movements and not to be associated with shoulder pain/injury. Additionally, the dominant shoulder exhibits muscular imbalance, which appears to be a significant risk factor for shoulder pain. Strengthening of the external rotators should be used alongside shoulder stretching and joint mobilisations, core strengthening and optimisation of spike technique as part of injury management and prevention programmes.

Effect of fatigue caused by a simulated handball game on ball throwing velocity, shoulder muscle strength and balance ratio: a prospective study

BACKGROUND

Arm throwing represents a deciding element in handball. Ball velocity, aim accuracy, and dynamic stability of the shoulder are factors that influence throwing effectiveness. The purpose of this study was to examine the influence of muscle fatigue caused by simulated game activities (SGA) on shoulder rotational isokinetic muscle strength, muscle balance and throwing performance, and to examine the relationship between muscle strength and throwing performance.

METHODS

Ten national elite adult handball athletes were evaluated. Isokinetic internal (IR), external (ER) rotators peak torque, and balance ratio were measured before and after SGA. Ball throwing velocity was assessed by radar gun.

RESULTS

Both internal (IR) and external (ER) rotators peak torque were significantly lower after SGA (p = 0.0003 and p = 0.02, respectively). However, the deleterious effect was more evident for IR than ER muscles (effect size r = 0.39 and r = 0.18, respectively). Balance ratio before and after SGA did not differ (p = 0.06). Ball throwing velocity was not impaired by SGA. Moreover, isokinetic variables correlated positively with ball velocity (r ≥ 0.67).

CONCLUSIONS

SGA affected the muscle strength of IR more than ER, predisposing the shoulder joint to muscular imbalance. The muscular impairment after SGA was insufficient to impair ball throwing velocity.

I.S.Mu.L.T - Rotator Cuff Tears Guidelines

Despite the high level achieved in the field of shoulder surgery, a global consensus on rotator cuff tears management is lacking. This work is divided into two main sessions: in the first, we set questions about hot topics involved in the rotator cuff tears, from the etiopathogenesis to the surgical treatment. In the second, we answered these questions by mentioning Evidence Based Medicine. The aim of the present work is to provide easily accessible guidelines: they could be considered as recommendations for a good clinical practice developed through a process of systematic review of the literature and expert opinion, in order to improve the quality of care and rationalize the use of resources.

An approach to identifying the effect of technique asymmetries on body alignment in swimming exemplified by a case study of a breaststroke swimmer

Despite the importance of maintaining good alignment to minimize resistive drag in swimming there is a paucity of literature relating to the effect of technique asymmetries on rotations of the body about a vertical axis (yaw). The purpose of this paper was to present an approach to analyzing the effect of technique asymmetries on rotations in swimming, exemplifying the process with a case study of a breaststroke swimmer. The kinematics and angular kinetics of an elite female international breaststroke swimmer performing a 'fatigue set' of four 100m swims were derived from digitized three-dimensional video data using a 13 segment body model. Personalised anthropometric data required to quantify accurately segment and whole body centres of mass and segmental angular momentum were obtained by the elliptical zone method. Five episodes of torques producing yaw occurred in the stroke cycle sampled for each 100m swim of this swimmer. These torques were linked to bilateral differences in upper limb kinematics during 1) out-sweep; 2) in-sweep; 3) upper limb recovery; and lower limb kinematics during 4) Lower limb recovery and 5) the kick. It has been shown that by quantifying whole body torques, in conjunction with the kinematic movement patterns, the effect of technique asymmetries on body alignment can be assessed. Assessment of individual swimmers in this manner provides a solid foundation for planning interventions in strength, flexibility, and technique to improve alignment and performance. Key pointsA unique (not been attempted previously) study of yaw in breaststroke swimming that yields new knowledge of how technique and strength asymmetries affects body alignment.Establishes an approach to investigation of yaw in swimming using 3D videography and inverse dynamics.Exemplifies the approach with a case study. The case study illustrated the potential of the approach to enable detailed assessment of yaw and to explain how the yaw is produced in terms of the asymmetries in speed and magnitude of the swimming actions.This procedure should be used to identify and quantify asymmetries that might impair performance.

Shoulder rotator muscle dynamometry characteristics: side asymmetry and correlations with ball-throwing speed in adolescent handball players

THE AIM OF THE INVESTIGATION WAS TO

1) compare shoulder external/internal rotator muscles' peak torques and average power values and their ratios in the dominant and non-dominant arm; 2) determine correlations between shoulder rotator muscles' peak torques, average power and ball-throwing speed in handball players. Fourteen 14 to 15-year-old male athletes with injury-free shoulders participated in the study (body height: 176 ± 7 cm, body mass 63 ± 9 kg). The tests were carried out by an isokinetic dynamometer system in the shoulder internal and external rotation movements at angular velocities of 60°/s, 90°/s and 240°/s during concentric contractions. The eccentric external- concentric internal rotator muscle contractions were performed at the velocity of 90°/s. The player threw a ball at maximal speed keeping both feet on the floor. The speed was recorded with reflected light rays. Training in handball does not cause significant side asymmetry in shoulder external/internal rotator muscle peak torques or the average power ratio. Positive correlations between isokinetic characteristics of the shoulder internal and external rotator muscles and ball-throwing speed were determined. The power produced by internal rotator muscles during concentric contractions after eccentric contractions of external rotator muscles was significantly greater in the dominant than in the non-dominant arm. Thus, it may be concluded that the shoulder eccentric external/concentric internal rotator muscle power ratio is significantly greater than this ratio in the concentric contractions of these muscles.