Rotation Strength Ratio Research Articles

Internal and External Rotators Muscle Strength Ratio and Acromio-Humeral Distance as Predictors of Shoulder Injuries in Volleyball Players

Abstract Purpose We aimed to investigate the ratio between strength of internal and external rotators of shoulder using handheld dynamometer and acromio-humeral distance actively and passively using musculoskeletal ultrasound to identify a relation between strength imbalance and shoulder joint injuries in Egyptian volleyball players. Methods A case control study, carried out on 60 volleyball players, subdivided into 2 subgroups, 30 with shoulder pain (injured group) and 30 apparently healthy players as a control group. The internal and external rotator muscles were measured with and held dynamometer, and acromio- humeral distance was measured using musculoskeletal ultrasound. Results injured group included 10 female players (33.3%) and 20 male players (66.7%), age ranged between 16-30 years old, while control group included 4 females (13.3%) and 26 males (86.7%). Internal and external rotation strength ratio was less than 0.9 in injured group in the dominant arm, in favor of the normal group with statistical difference between them (p < 0.004). Acromio-humeral distance actively in injured group ranged from 0.45 to 0.87cm with mean ±SD of (0.64±0.07), less than normal group which ranged from 0.7 to 1cm with a mean ±SD of (0.79±0.08) (p < 0.000) Conclusion Weakness of external rotators muscles strength will decrease ratio between external rotator/internal rotator muscles, reducing the acromio-humeral distance especially during abduction, leading to shoulder injuries among volleyball players.

Exploring the interplay of trunk and shoulder rotation strength: a cross-sport analysis.

Introduction: Trunk and shoulder strength are consistently shown to be involved in performance limitations, as well as contributing to stability, power output, and reducing the risk of injury. Although their biomechanical interaction is a critical aspect for athletes, there is limited research on the relationship between trunk and shoulder strength in sports where upper body mechanics are critical for optimal performance. Purpose: This study examined the differences and relationships between trunk rotational strength and shoulder rotational strength among athletes participating in mixed martial arts (MMA), tennis, swimming, and baseball. Methods: Maximal voluntary contraction tests were performed to evaluate strength of 39 professional adult male athletes from disciplines of MMA (n = 6), tennis (n = 11), swimming (n = 11) and baseball (n = 11). Peak force data were used in sports comparison and relationship analysis between trunk and shoulder rotation strength parameters. Results: The findings revealed a complex and significant relationship between trunk and shoulder strength, with unique patterns for each athletic discipline. Tennis players exhibited a strong correlation between trunk bilateral differences and internal shoulder rotation, while other disciplines demonstrated a more balanced use of trunk asymmetry. Swimmers displayed the best interactions between trunk and shoulder overall, emphasizing the aquatic environment's biomechanical demands. In MMA, the strongest correlation was between shoulder internal and external rotation with the trunk, mainly due to the number of defensive movements in addition to offensive ones. Baseball pitchers showed a significant correlation between internal/external shoulder rotation strength ratio and trunk asymmetry. Conclusion: While no differences in peak force variables were found, unique relationships between trunk and shoulder rotational performance were discovered. The results suggest a long-term sport-specific adaptation of the trunk-shoulder interaction in sports that require upper limb power movements. It seems, that the relationship between the various parameters of trunk and shoulder was influenced by the movement stereotype of each sport. Therefore, recognition of sport-specific interactions is critical to the development of effective training programs that enhance performance and potentially reduce injury risk in different sports. Researchers and practitioners should focus on longitudinally monitoring fluctuations in TRS and SRS relationships throughout each sport season and examining potential associations with injury incidence.

Upper and Lower Body Strength Asymmetries and Shoulder Rotation Strength Ratio in Youth Tennis Players Using Isokinetic Testing

Upper and Lower Body Strength Asymmetries and Shoulder Rotation Strength Ratio in Youth Tennis Players Using Isokinetic Testing

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.

Clinical shoulder measurements related to joint loads in collegiate pitchers

Pitchers are prone to upper extremity injury due to repetitive high joint loads. Clinical measures of shoulder strength and range of motion (ROM) have shown links to injury risk in pitchers, however, these factors have rarely been studied in relation to throwing joint loads. The purpose of this study was to identify which clinical ROM and isokinetic strength variables were related to peak shoulder and elbow joint torques in collegiate pitchers. Thirty-three healthy collegiate pitchers participated in this study. Fastball velocity, shoulder concentric and eccentric strength, and passive shoulder ROM variables were analyzed using a Lasso regression to determine what factors influenced shoulder internal rotation torque and elbow varus torque. Fastball velocity was selected by the Lasso as indicator of increased shoulder and elbow torque. Passive shoulder external rotation ROM was also selected as an important factor in joint loading with increased shoulder external rotation ROM being related to lower joint loads. The bilateral ratio of shoulder internal rotator concentric strength was related to peak shoulder and elbow torques with an increase in the bilateral ratio of shoulder strength leading to reduced joint torques. Increases in the eccentric external rotator to concentric internal rotator strength (functional ratio) of the dominant arm and increases in dominant arm eccentric internal rotator strength were both related to increases in each joint torque. Results from the study indicate that pitch speed, passive shoulder external rotation ROM, and the isokinetic shoulder strength profile including internal rotator strength and functional strength ratio of pitchers are related to joint loading during the pitch and may be important to monitor in relation to injury risk and/or during rehabilitation. These results provide insight into the role that both shoulder ROM and rotator cuff strength play in the dynamic stabilization of the elbow and shoulder during pitching.

Comparison of Shoulder Total Rotational Range of Motion and External to Internal Rotation Strength Ratio between Assembly Line Workers with and without Subacromial Pain Syndrome

Background Subacromial pain syndrome (SAPS) is one of the causes of shoulder pain in workers performing repetitive upper extremity movements. However, there have been no studies on physical characteristics such as shoulder total rotational range of motion (ROM) and external to internal rotation muscle strength ratio of workers. Purpose The purpose of this study was to compare the total rotational ROM and external to internal rotation muscle strength ratio in workers with and without SAPS. Study design A cross-sectional study Methods This study included 35 workers with SAPS and 32 workers without SAPS. The total rotational ROM were measured using Smart KEMA motion sensor, and external to internal rotation muscle strength were measured using Smart KEMA pulling sensor. Results The results showed that there were significant differences in the total rotation ROM between the groups (<italic>p</italic>&lt;0.05). However, no significant difference was found in the external to internal rotation muscle strength ratio (<italic>p</italic>&gt;0.05). Conclusions Assembly line workers with SAPS had limited total rotational ROM. However, the ratio of external to internal rotation muscle strength ratio was not different for workers without SAPS. These characteristics can be considered factors that should be considered in evaluating workers with SAPS and establishing a treatment plan.

Relationship Differences in Pre-season Isometric Shoulder Strength, Humeral Torsion and Shoulder Range of Motion in Collegiate Baseball Players (218)

Objectives:Muscle strength, humeral torsion (HT) and shoulder range of motion (ROM) have been linked to throwing performance and injury risk in baseball players. Research suggests that players who demonstrate an isometric shoulder external rotation (ER)/internal rotation (IR) strength ratio of <0.75 are at a higher risk for developing a throwing-related upper extremity injury. While the relationships between HT and shoulder ROM have been examined in the literature, few studies have examined the potential relationships between these variables and isometric shoulder strength. The purpose of this study was to examine the relationships between isometric shoulder strength, HT and shoulder ROM at the start of each baseball season in a cohort of healthy junior college baseball players.Methods:Ninety-two healthy junior college baseball players (mean age=19.9±0.8 years) were prospectively assessed at the start of 2 consecutive spring seasons. Variables measured included HT, shoulder ROM and isometric shoulder strength. Both the dominant (D) and non-dominant (ND) shoulders of each player were assessed throughout the study. Chi square tests and bivariate Pearson correlation coefficients were calculated to examine between group differences and the relationships between variables. Statistical significance was set a priori at α=0.05.Results:33.7% of junior college players demonstrated a D shoulder ER/IR strength ratio of <0.75 at the start of baseball season. Pitchers and position players demonstrated no significant differences in D shoulder ER/IR strength ratios at the start of the season (P=.40). Additionally, moderate positive relationships were observed between D HT and D IR ROM (r=0.35; P=.001) as well as D horizontal adduction (HA) ROM (r=0.43; P<.001). A moderate relationship was also observed between ND HT and ND IR ROM (r=0.56, P<.001), however ND ER and HA ROM demonstrated weaker relationships respectively (ER: r=-0.27; P=.01; HA: r=0.26; P=.01). Inverse relationships were observed between HT and ER strength in both the D and ND shoulders (D: r=-0.27, P=.01; ND: r=-0.28, P=.007). Internal rotation ROM was also inversely correlated with ER strength (r=-0.29, P=0.005) and ER/IR strength ratios (r=-0.31, P=.003), but only in the D shoulder. No significant correlations were observed between ROM and strength in the ND shoulder.Conclusions:One third of the junior college baseball players in this study began the season with marked deficits in D shoulder strength, irrespective of their position. We then examined the relationships between HT, shoulder ROM and isometric shoulder strength and confirmed the previously established correlation between HT and shoulder ROM. Moreover, there appeared to be inverse relationships between HT and ER strength in both the D and ND shoulders as well as IR ROM and ER strength in the D shoulder. This study emphasizes the importance of pre-season rotator cuff strength training, with an emphasis on improving ER strength, to potentially aid in the prevention of throwing-related upper extremity injuries in collegiate baseball players. Humeral torsion and shoulder ROM may influence isometric shoulder strength, however more research is needed to better understand these relationships in the throwing shoulder.

Relationship between single-leg stance test with light touch and hip muscle strength in healthy young adults.

[Purpose] This study investigated the relationship between the single-leg stance test with light touch and hip rotator muscle strength. [Participants and Methods] Thirty-one healthy young adults participated in the study. A single leg stance test with light touch was performed to evaluate the participants’ static balance ability. The duration that an individual could successfully perform the single leg stance test with light touch in the eyes open was measured. The participants were instructed to slightly touch their right index fingertip on the digital scale. The hip muscle strength of the internal rotators and external rotators were measured by the isometric peak torque. The internal/external rotator strength ratio was calculated by dividing the strength of the internal rotator by that of the external rotator. [Results] The hip external rotator muscle strength was higher in males than in females. Moreover, there was a significant correlation between the single-leg stance test with light touch and hip external rotator muscle strength in males and between the single leg stance test with light touch and hip internal rotator muscle strength in females. Furthermore, a significant positive correlation was found between the single leg stance test with light touch and hip internal rotator/external rotator ratio in males. [Conclusion] We concluded that the single leg stance test with light touch is a useful tool to evaluate static hip muscle strength.

Change of Direction Performance Is Influenced by Asymmetries in Jumping Ability and Hip and Trunk Strength in Elite Basketball Players

Change of direction (COD) ability is essential for sport performance in high level team sports such as basketball, however, the influence of asymmetries on COD ability is relatively unknown. Forty-three junior and senior level elite basketball players performed isometric hip and trunk strength testing, passive hip and trunk range of motion testing, and unilateral horizontal and vertical jumps, as well as the T-test to measure COD performance. Mean asymmetry values ranged from 0.76% for functional leg length up to 40.35% for rate of torque development during hip flexion. A six-variable regression model explained 48% (R2 = 0.48; p &lt; 0.001) of variation in COD performance. The model included left hip internal/external rotation strength ratio, and inter-limb asymmetries in hip abduction rate of torque development, hip flexion range of motion, functional leg length, single leg triple jump distance, and peak torque during trunk lateral flexion. Results suggest that the magnitude of asymmetries is dependent of task and parameter, and using universal asymmetry thresholds, such as &lt;10 %, is not optimal. The regression model showed the relationship between asymmetries and COD performance. None of tests were sufficient to explain a complex variable like COD performance.

External rotator strength deficits in non-athletic people with rotator cuff related shoulder pain are not associated with pain intensity or disability levels

BackgroundStrength deficits are often reported in people with rotator cuff related shoulder pain. However, these have mainly been tested in athletic populations and pain interference with testing has not been considered. ObjectivesTo examine strength without pain interference in non-athletic people with rotator cuff related shoulder pain and its association with pain intensity and disability. DesignCross-sectional study. MethodsSixty-seven participants with rotator cuff related shoulder pain were assessed for isometric strength of shoulder external rotator and internal rotator muscles without pain interference with a hand-held dynamometer. Strength was normalized (%body weight). Differences in external and internal rotation strength and external:internal rotator strength ratio between symptomatic and asymptomatic sides were examined (Independent t-tests, Wilcoxon rank sum tests). Spearman's rank correlation coefficients were used to examine associations between strength and pain and disability levels. ResultsThere was no significant difference in internal rotator strength normalized to body weight between symptomatic and asymptomatic sides. There was a significant difference in external rotator strength normalized to body weight (p < .001) and external:internal ratio (p < .001) between sides. No significant correlations were found between strength and pain or disability levels. ConclusionNon-athletic people with rotator cuff related shoulder pain had external rotator strength deficits without pain interference during strength testing, which were not associated with pain and disability levels.

Is the Normal Shoulder Rotation Strength Ratio Altered in Elite Swimmers?

It is commonly believed that the shoulder external rotation (ER) to internal rotation (IR) strength ratio is decreased in swimmers due to predominant IR loading during the pull-through (propulsive) phase which predisposes to shoulder pain. However, the evidence supporting this hypothesis is inconclusive. Therefore, the aim of this study was to examine shoulder rotation strength parameters in elite swimmers and investigate potential associations with shoulder pain. Sixty-eight (40 men; age, 19.9 ± 3.2 yr) elite swimmers provided demographic and shoulder pain history data before measurement of shoulder rotation strength. Mixed model analyses were used to examine differences in shoulder IR and ER strength normalized to body weight (BW) and the shoulder rotation strength ratio. A multinomial logistic regression model was utilized to examine associations between shoulder rotation strength parameters and shoulder pain. Mean shoulder IR strength (BW) was approximately 0.29 for male swimmers and 0.26 for female swimmers. Mean shoulder ER strength (BW) was approximately 0.19 for male swimmers and 0.18 for female swimmer. The shoulder ER/IR strength ratio was approximately 0.70 bilaterally for all swimmers. There were no significant differences between dominant and nondominant shoulders in IR or ER strength normalized to BW (P ≥ 0.547). There were no associations between any shoulder strength parameters and shoulder pain (r = 0.032, P = 0.107). Despite the high IR loading, optimal swimming technique does not alter the normal ER/IR strength ratio at the shoulder. Elite swimmers who report current or a history of shoulder pain demonstrate normal shoulder rotation strength ratios. The finding of symmetrical shoulder rotation strength points to side-to-side strength comparisons as a valuable clinical tool in managing swimmers with unilateral shoulder pain.

Comparison of the Shoulder External Rotator Strength and Asymmetry Ratio Between Workers With and Without Shoulder Impingement Syndrome.

Kim, J-H, Kwon, O-Y, Hwang, U-J, Jung, S-H, Ahn, S-H, and Kim, H-A. Comparison of shoulder external rotator strength and the asymmetry ratio between workers with and without shoulder impingement syndrome. J Strength Cond Res 35(12): 3364-3369, 2021-Shoulder impingement syndrome (SIS) is the most common shoulder problem causing shoulder pain. Several studies have indicated that shoulder external rotator muscles provide dynamic stability to the shoulder joint. However, the relationship of SIS to changes in shoulder external rotator muscle strength remains controversial. The purpose of the study was to compare the shoulder external rotator strength and asymmetry ratio between workers with SIS and the normal group in a side-lying position. Twelve male industrial workers with SIS and the normal group of 12 workers participated in this study. A pulling sensor measured shoulder external rotator muscle strength in a side-lying position with the shoulder at 0° and 90° of flexion. The asymmetry ratio was calculated by a specific formula using the shoulder external rotator muscle strength of the dominant side and the unaffected side. Two-way analysis of variance was used to determine between-group differences in shoulder external rotator muscle strength and the asymmetry ratio among the 2 positions. Subjects with SIS did not exhibit significant differences in shoulder external rotator muscle strength in the side-lying position with the shoulder at 0° and 90° of flexion relative to the normal group. However, subjects with SIS had a significantly increased asymmetry ratio of shoulder external rotation strength in the side-lying position with the shoulder at 90° of flexion compared with the normal group. In conclusion, workers with SIS had an asymmetry of shoulder external rotator strength in side-lying with the shoulder at 90° of flexion.

Morphofunctional upper limb asymmetries in young tennis players: the role of maturity status

The aim of this study was to check for upper limb volume asymmetry and strength ratio of shoulder muscle rotators in young tennis players. A total of 21 young male tennis players took part in the study. Subjects’ maturity status was determined using predicted age at peak height velocity (PHV); thus, the sample was divided into two groups: negative maturity offset values (PREPHV; n = 9) and positive values, including 0 (POSTPHV; n = 12). Upper limb volumes were estimated using the truncated cone method. Concentric peak torque in the external and internal shoulder rotations was determined using an isokinetic dynamometer at 60o.s−1. The external to internal rotation ratio was also calculated. There was morphological upper limb asymmetry in both groups (p < 0.05), with no difference between the groups. However, only the POSTPHV group presented shoulder strength asymmetry. External to internal rotation ratios were 76% and 89% for dominant and nondominant arms, respectively, in the POSTPHV group. PHV seems to be a critical period for functional asymmetry in young tennis players, particularly the internal rotation strength and conventional ratio of shoulder rotation. Thus, an assessment of shoulder rotator strength is required to monitor its progression and avoid the risk of injury in the dominant rotator cuff.

Asymmetry of dominant and non-dominant shoulders in university level men and women volleyball players

PurposeVolleyball involves repetitive forceful actions predominantly of one arm, which could eventually lead to an injury or shoulder pathology. The aim of the study was to compare the range of motion and strength in the dominant and non-dominant shoulders of university level volleyball players, with the objective of examining any differences between sexes.MethodsA total of 19 university level volleyball players (9 men: 81.3 ± 8.0 kg, 21 ± 1 years; 10 women: 66.0 ± 8.2 kg, 19 ± 1 years) participated. The passive internal and external range of motion of the dominant and non-dominant spiking shoulders were measured with a goniometer. The shoulder strength tests were performed on an isokinetic dynamometer at the speed of 60°/s in the concentric mode of contraction. Shoulder internal and external rotator concentric strength, range of motion, and internal/external rotation strength ratios were tested between arm dominance and sex with the use of 2-way mixed design ANOVA.ResultsInternal and external rotation strength was asymmetrical in both men and women, in favour of the dominant side (&lt;i&gt;p&lt;/i&gt; &lt; 0.05). Both men and women displayed asymmetrical external/internal ratios (&lt;i&gt;p&lt;/i&gt; &lt; 0.05), with greater ratios present in the non-dominant side.ConclusionsUniversity level men and women volleyball players exhibit similar levels of significant asymmetry in the internal/external rotation strength between dominant and non-dominant spiking arms. Furthermore, subject-specific responses in strength asymmetries suggest further investigation at the individual level. Isokinetic shoulder screening could be used to reveal information about possible risk factors for shoulder injuries.

Does My Patient With Shoulder Pain Have a Rotator Cuff Tear?: A Predictive Model From the ROW Cohort.

Background:Rotator cuff tears are the leading cause of shoulder pain and disability. However, the diagnosis of a rotator cuff tear based on patient characteristics, symptoms, and physical examination findings remains a challenge because of a lack of data. Moreover, data on the predictive ability of a combination of these characteristics and tests are not available from a large cohort of patients. Consequently, clinicians rely on expensive imaging, such as magnetic resonance imaging (MRI), to make a diagnosis.Purpose:To model patient characteristics, symptoms, and physical examination findings that predict a rotator cuff tear. We present a nomogram based on our predictive model that can be used in patients with shoulder pain to determine the probability of the diagnosis of a rotator cuff tear without the need for imaging.Study Design:Cohort study (diagnosis); Level of evidence, 2.Methods:We recruited patients from outpatient clinics who were ≥45 years of age and who had shoulder pain of at least 4 weeks’ duration. A rotator cuff tear was diagnosed based on expert clinical impression and the presence/absence of a tear on a blinded review of MRI. Ultimately, 301 patients were included in the analysis.Results:A total of 123 patients (41%) had rotator cuff tears, and 178 patients (59%) did not. The predictors of the diagnosis of a rotator cuff tear included external rotation strength ratio of the affected versus unaffected shoulder (odds ratio [OR], 1.20 [95% CI, 1.08-1.34]), male sex (OR, 1.98 [95% CI, 1.10-3.56]), positive lift-off test result (OR, 4.33 [95% CI, 1.46-12.86]), and positive Jobe test result (OR, 9.19 [95% CI, 4.69-17.99]). A nomogram based on these predictor variables was plotted.Conclusion:Presented is a model that can accurately predict the diagnosis of a rotator cuff tear with satisfactory discrimination and calibration based on 4 variables: sex, lift-off test, Jobe test, and external rotation strength ratio. Data from this study can be used to aid in the diagnosis of a rotator cuff tear in day-to-day clinical practice in outpatient settings without the need for expensive imaging such as MRI.

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.

Prevalence of Glenohumeral Internal Rotation Deficit and its Association with Scapular Dyskinesia and Rotator Cuff Strength Ratio in Collegiate Athletes Playing Overhead Sports

Introduction: Glenohumeral Internal Rotation Deficit (GIRD) indicates a 15° or greater loss of internal rotation of the throwing shoulder compared with the non-dominant shoulder.Aim: To estimate the prevalence of GIRD in collegiate overhead sports player and determine whether GIRD is associated with scapular dyskinesia and rotator cuff strength ratio. Materials and Methods: The present study was a Cross-sectional study. A total of 127 collegiate athletes were assessed for passive range of motion, external to internal rotation strength ratio (ER/IR ratio) and scapular dyskinesia for the throwing and non-throwing shoulder. Internal and external rotation of shoulder was measured using an inclinometer with the subject in prone and arm abducted to 90°. Scapular dyskinesia was measured using Lateral Scapula Slide test (LSST) and external to internal rotator strength was measured using a held hand isometric dynamometer. Chi-square test was used to find the association between GIRD and scapular dyskinesia and rotator cuff strength ratio.Results: Prevalence of GIRD (n=37) was found to be 29.1%. GIRD was not found to be associated with Scapular dyskinesia (p=0.237) and ER/IR strength ratio (p=0.411).Conclusion: Prevalence of GIRD in collegiate athletes playing overhead sports was found to be 29.1% and there was no association of GIRD with scapular dyskinesia, rotator cuff strength ratio.

HAMSTRING MORPHOLOGY AND STRENGTH REMAIN ALTERED 2 YEARS FOLLOWING A HAMSTRING GRAFT IN ACL RECONSTRUCTION

Background:The hamstring graft used in anterior cruciate ligament (ACL) reconstruction has been shown to lead to changes to the semitendinosus and gracilis musculature. This study further evaluated the effect of the surgery on hamstring muscle morphology and knee muscle strength at 2 years post-surgery.Hypotheses:(1) Loss of donor muscle size would significantly correlate with knee muscle strength deficits (2) Loss of donor muscle size would be greater for muscles that do not experience tendon regeneration, and (3) Morphological adaptations would also be evident in non-donor knee muscles.Study Design:Cross sectional evaluation.Methods:20 participants (14 male, 6 female, 29 ± 7 years, 82 ± 15 kg) that had undergone a hamstring graft in ACL reconstruction at least two years previously, underwent bilateral MRI and subsequent strength testing. Muscle and tendon volumes, peak CSA’s and lengths were determined for 12 muscles and 6 functional muscle groups of the surgical and contralateral limbs. Peak isokinetic concentric strength was measured in knee flexion/extension and internal/external tibial rotation.Results:Only 50% of the patients regenerated both the semitendinosus and gracilis tendons. The regenerated tendons were longer with larger volume and CSA compared to the contralateral side. Deficits in semitendinosus and gracilis muscle size were greater for tendons that did not regenerate. In addition, combined hamstrings (semitendinosus, semimembranosus, biceps femoris) and combined medial knee muscles (semitendinosus, semimembranosus, gracilis, vastus medialis, medial gastrocnemius, sartorius) on the surgical side were reduced in volume by 12% and 10% respectively. A 7% larger volume was observed in the surgical leg for the biceps femoris and corresponded with a lower internal/external tibial rotation strength ratio. The difference in volume, peak CSA and length of the semitendinosus and gracilis correlated significantly with the deficit in knee flexion strength with Pearson correlations of 0.51, 0.57 and 0.61 respectively.Conclusion:The muscle-tendon properties of the semitendinosus and gracilis are substantially altered following harvesting, and these alterations may contribute to knee flexor weakness in the surgical limb. These deficits are more pronounced in tendons that do not regenerate and are only partially offset by compensatory hypertrophy of other hamstring muscles.Clinical Relevance:Surgeons should consider muscle retraction of the hamstring following tendon harvest in their choice of graft option for ACL reconstruction.

RISK FACTORS FOR OVERUSE SHOULDER INJURIES AMONG 329 ELITE HANDBALL PLAYERS: A PROSPECTIVE COHORT STUDY

BackgroundShoulder injuries are common among handball players and are dominated by overuse characteristics.ObjectiveAssess the effect of three previously identified risk factors for shoulder problems (reduced glenohumeral rotation, external rotation weakness...

Physical Exam Risk Factors for Lower Extremity Injury in High School Athletes: A Systematic Review.

A stated goal of the preparticipation physical evaluation (PPE) is to reduce musculoskeletal injury, yet the musculoskeletal portion of the PPE is reportedly of questionable use in assessing lower extremity injury risk in high school-aged athletes. The objectives of this study are: (1) identify clinical assessment tools demonstrated to effectively determine lower extremity injury risk in a prospective setting, and (2) critically assess the methodological quality of prospective lower extremity risk assessment studies that use these tools. A systematic search was performed in PubMed, CINAHL, UptoDate, Google Scholar, Cochrane Reviews, and SportDiscus. Inclusion criteria were prospective injury risk assessment studies involving athletes primarily ages 13 to 19 that used screening methods that did not require highly specialized equipment. Methodological quality was evaluated with a modified physiotherapy evidence database (PEDro) scale. Nine studies were included. The mean modified PEDro score was 6.0/10 (SD, 1.5). Multidirectional balance (odds ratio [OR], 3.0; CI, 1.5-6.1; P < 0.05) and physical maturation status (P < 0.05) were predictive of overall injury risk, knee hyperextension was predictive of anterior cruciate ligament injury (OR, 5.0; CI, 1.2-18.4; P < 0.05), hip external:internal rotator strength ratio of patellofemoral pain syndrome (P = 0.02), and foot posture index of ankle sprain (r = -0.339, P = 0.008). Minimal prospective evidence supports or refutes the use of the functional musculoskeletal exam portion of the current PPE to assess lower extremity injury risk in high school athletes. Limited evidence does support inclusion of multidirectional balance assessment and physical maturation status in a musculoskeletal exam as both are generalizable risk factors for lower extremity injury.