Rotation Strength Ratio Research Articles

Morphologic Characteristics and Strength of the Hamstring Muscles Remain Altered at 2 Years After Use of a Hamstring Tendon Graft in Anterior Cruciate Ligament Reconstruction

Background: The hamstring tendon graft used in anterior cruciate ligament (ACL) reconstruction has been shown to lead to changes to the semitendinosus and gracilis musculature. Hypothesis: We hypothesized that (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 nondonor knee muscles. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Twenty participants (14 men and 6 women, mean age 29 ± 7 years, mean body mass 82 ± 15 kg) who had undergone an ACL reconstruction with a hamstring tendon graft at least 2 years previously underwent bilateral magnetic resonance imaging and subsequent strength testing. Muscle and tendon volumes, peak cross-sectional areas (CSAs), 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 35% of the patients showed regeneration of both the semitendinosus and gracilis tendons. The regenerated tendons were longer with larger volume and CSA compared with the contralateral side. Deficits in semitendinosus and gracilis muscle size were greater for muscles in which tendons did not regenerate. In addition, combined hamstring muscles (semitendinosus, semimembranosus, and biceps femoris) and combined medial knee muscles (semitendinosus, semimembranosus, gracilis, vastus medialis, medial gastrocnemius, and sartorius) on the surgical side were reduced in volume by 12% and 10%, respectively. A 7% larger volume was observed in the surgical limb for the biceps femoris muscle 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 after harvesting, and these alterations may contribute to knee flexor weakness in the surgical limb. These deficits are more pronounced in knees with tendons that do not regenerate and are only partially offset by compensatory hypertrophy of other hamstring muscles.

Reliability and Validity of EN-TreeM Dynamometer for Measurement of Shoulder Rotator Strength in Volleyball Players.

Volleyball involves repeated forceful arm actions that produce a high incidence of shoulder injury. Shoulder rotator strength ratio is an important predictor of the likelihood of shoulder injury, especially, secondary shoulder impingement and instability. Therefore, assessment of muscle strength of external and internal rotators of shoulder is imperative to establish the profiles of shoulder rotator performance, strength ratios, and shoulder mobility of volleyball players. To establish reliability and validity of EN-TreeM dynamometer for the measurement of shoulder rotators strength in volleyball players. Thirty male volleyball players aged 18-24 years, mean height 1.7m, weight 69.8 Kg and BMI 23.1 participated in the study. They performed 1RM (one repetition maximum) estimation protocols using EN-TreeM dynamometer and free weights for shoulder rotators, to investigate its concurrent validity. A retest using the same protocol was performed 48 hours later to assess test-retest reliability of the EN-TreeM dynamometer. The results yielded excellent test-retest reliability (ICC0.96) and internal consistency (Cronbach's alpha0.98) for both internal and external rotators. The concurrent validity was established using Pearson correlation coefficient (internal rotator r=0.45, p=0.01;External rotator r=0.38, p=0.03). The findings establish the reliability and concurrent validity of EN-TreeM dynamometer for the quantification of shoulder rotators strength. Based on these findings in volleyball players, EN-TreeM dynamometer can be used with confidence as an instrument for assessing muscle performance (strength). Additionally, it may also be used for monitoring changes due to rehabilitation interventions in shoulder injuries.

Residual Impact of Previous Injury on Musculoskeletal Characteristics in Special Forces Operators.

BackgroundMusculoskeletal injuries are a significant burden to United States Army Special Operations Forces. The advanced tactical skill level and physical training required of Army Special Operators highlights the need to optimize musculoskeletal characteristics to reduce the likelihood of suffering a recurrent injury.PurposeTo identify the residual impact of previous injury on musculoskeletal characteristics.Study DesignCross-sectional study; Level of evidence, 3.MethodsIsokinetic strength of the knee, shoulder, and back and flexibility of the shoulder and hamstrings were assessed as part of a comprehensive human performance protocol, and self-reported musculoskeletal injury history was obtained. Subjects were stratified based on previous history of low back, knee, or shoulder injury, and within-group and between-group comparisons were made for musculoskeletal variables.ResultsKnee injury analysis showed no significant strength or flexibility differences. Shoulder injury analysis found internal rotation strength of the healthy subjects (H) was significantly higher compared with injured (I) and uninjured (U) limbs of the injured group (H, 60.8 ± 11.5 percent body weight [%BW]; I, 54.5 ± 10.5 %BW; U, 55.5 ± 11.3 %BW) (P = .014 [H vs I] and P = .05 [H vs U]). The external rotation/internal rotation strength ratio was significantly lower in the healthy subjects compared with injured and uninjured limbs of the injured group (H, 0.653 ± 0.122; I, 0.724 ± 0.121; U, 0.724 ± 0.124) (P = .026 [H vs I] and P = .018 [H vs U]). Posterior shoulder tightness was significantly different between the injured and uninjured limb of the injured group (I, 111.6° ± 9.4°; U, 114.4° ± 9.3°; P = .008). The back injury analysis found no significant strength differences between the healthy and injured groups.ConclusionFew physical differences existed between operators with prior knee or back injury. However, operators with a previous history of shoulder injury demonstrated significantly less shoulder strength than uninjured operators as well as decreased shoulder flexibility on the injured side. All operators, regardless of prior injury, must perform the same tasks; therefore, a targeted injury rehabilitation/human performance training specifically focused on internal rotation strength and tightness of the posterior capsule may help reduce the risk for recurrence of injury. Operators presenting with musculoskeletal asymmetries and/or insufficient strength ratios may be predisposed to musculoskeletal injury.Clinical RelevanceSpecific fitness programs to compensate for deficiencies in strength and flexibility need to be designed that may reduce the risk of injuries in Special Forces Operators.

Identification Of Asymmetrical And Suboptimal Agonist/antagonist Strength In A Cohort Of Special Forces Soldiers

Unilateral strength training has gained significant interest within the military as an adopted training principle. Theoretically, unilateral strength training should promote similar bilateral and unilateral agonist/antagonist synergy by limiting the dominant limb’s support of total workload. PURPOSE: To identify asymmetrical and non-synergistic strength in a cohort of Special Forces Soldiers. METHODS: A total of 86 Special Forces Soldiers participated. Isokinetic strength of the knee and shoulder was assessed as part of a comprehensive human performance protocol. The proportion of individual bilateral differences (>10% difference) was calculated for each joint and variable. The proportion of insufficient strength ratios was calculated based on established normative clinical data. RESULTS: Individual bilateral strength differences were identified in 45.1% of subjects for knee flexion and 43.1% for knee extension. An insufficient knee flexion/extension ratio was identified in 43.1% of Soldiers. Individual bilateral strength differences were identified in 45.3% of subjects for internal rotation and 35.8% for external rotation. Insufficient external rotation/internal rotation strength ratios were identified in 35.8-49.1% of Soldiers. CONCLUSION: A high proportion of Soldiers demonstrated bilateral asymmetry > 10%. This threshold has been previously identified as a risk factor for musculoskeletal injury and may compromise physical readiness. Soldiers presenting with musculoskeletal asymmetries and/or insufficient strength ratios may be predisposed to musculoskeletal injury. Both of these scenarios may limit physical readiness at the individual and unit level. Individuals demonstrating asymmetrical or insufficient strength ratios may benefit from unilateral strength training. Opinions, interpretations, conclusions, and recommendations are those of the author and not necessarily endorsed by the Department of Defense, US Army, or US Army Special Operations Command. Supported by USAMRMC #W81XWH-11-2-0020.

The changes in shoulder rotation strength ratio for various shoulder positions and speeds in the scapular plane between baseball players and non-players.

[Purpose] This study aimed to investigate the effect of shoulder positions and speeds on internal and external rotation torque of college baseball players and age-matched non-players. [Subjects] Twenty first-level collegiate baseball players and 19 college students were recruited. [Methods] A dynamometer system was used to evaluate the shoulder rotation strength in sitting postures. Three testing positions, namely shoulder abduction of 45°, 70°, and 90° in the scapular plane, were combined with three testing speeds at 60°/s, 120°/s, and 210°/s. [Results] The maximum external and internal rotation torques both occurred at shoulder abduction of 70°. However, only external rotation torque was affected by the speed, with the peak value observed at 60°/s. The internal rotation torque of baseball players was larger than that of the control group under all testing conditions, but the external rotation did not show any difference. The ratio of external to internal rotation torque changed with the testing positions and speeds in both groups. The ratio in the control group was greater than that in the player group. [Conclusion] The shoulder position could affect the rotational strength, and the baseball players could strengthen their external rotators for better performance and injury prevention.

Reliability of hand held dynamometry compared to externally fixed dynamometry for shoulder internal and external rotation strength ratios

Reliability of hand held dynamometry compared to externally fixed dynamometry for shoulder internal and external rotation strength ratios

Posterior shoulder tightness and rotator cuff strength assessments in painful shoulders of amateur tennis players

Previous studies have shown a relationship between shoulder posterior capsule tightness and shoulder pain in overhead athletes. However, this relationship has not been studied in tennis players. Assessment of the shoulder range of motion (ROM), strength and posterior capsule tightness of skilled amateur tennis players who had complaints of dominant shoulder pain in comparison with tennis players without pain. Forty-nine skilled amateur tennis players were distributed in 2 groups: Control Group (n=22) and Painful Group (n=27). The first group was composed of asymptomatic subjects, and the second was composed of subjects with shoulder pain on the dominant side. These groups were evaluated to determine the dominant and non-dominant shoulder ROM (internal and external rotation), isometric shoulder strength (internal and external rotation) and posterior shoulder tightness by blind evaluators. The ANOVA results indicated significant differences between the groups in the dominant shoulder ROM, posterior capsule tightness, external rotation strength and strength ratio (p<0.05). The intragroup analysis (dominant versus non-dominant) in the Painful Group displayed a significant difference for ROM, posterior capsule tightness and external rotation strength (p<0.05). The tennis players with pain in the dominant shoulder presented greater posterior capsule tightness, internal rotation deficit (ROM), external rotation gain (ROM) and deficits in external rotation strength than the tennis players without pain.

The effect of infraspinatus hypotrophy and weakness on the arthroscopic treatment of spinoglenoid notch cyst associated with superior labrum anterior-to-posterior lesions

Patients with spinoglenoid notch cyst associated with superior labrum anterior-to-posterior (SLAP) lesions were evaluated. The patients were all treated by arthroscopic cyst decompression combined with SLAP repair. The hypothesis of the study was that the patients who underwent prolonged conservative treatment period prior to surgery would exhibit significant infraspinatus hypotrophy and weakness, and their postoperative clinical and functional outcomes would be less satisfactory. Sixteen patients exhibited positive MRI and EMG findings with clinical signs of weakness and pain. The median age was 40.5years (range 32-52), and the study group consisted of 11 males and 5 females with a median follow-up period of 26months (12-48). The median duration of symptoms and conservative treatment prior to the surgical intervention was 3.5months (1-14). Seven patients in group A exhibited infraspinatus hypotrophy. Group B comprised 9 patients without infraspinatus hypotrophy. The results of the pre- and postoperative Constant scores, visual analogue scale (VAS) scores, and external rotation strength test rates were compared between groups. They all improved in terms of pain, strength, and function (P<0.05). Significant differences were observed between the pre- and postoperative external rotation strengths and Constant scores (P<0.05). However, no significant difference was observed between the pre- and postoperative VAS scores (n.s.). A significant correlation was observed in group A between surgical timing, the preoperative external rotation strength ratio (P=0.04) and the postoperative VAS scores (P=0.013). The arthroscopic treatment was satisfactory with good clinical outcomes. Infraspinatus hypotrophy occurred in cases of prolonged surgical duration and significantly affected external rotation strength and functional outcomes. Retrospective comparative study, Level III.

Improvements in Shoulder Endurance Following a Baseball-Specific Strengthening Program in High School Baseball Players

Background:The posterior shoulder muscles play key roles in maintaining shoulder function in throwing. Arm fatigue has been identified as a risk factor for shoulder and elbow pain in youth baseball pitchers. However, endurance of the posterior shoulder muscles in overhead athletes is not routinely examined or conditioned.Hypothesis:Upper extremity muscular endurance can be improved in adolescent baseball players during a 20-week preseason training program. Secondarily, strength will be improved. Finally, these improvements will be associated with maintenance of range of motion.Study Design:Cohort study.Methods:Fourteen baseball players (age, 16 ± 2 years) attended 3 supervised training sessions per week for 20 weeks. Strengthening of the upper extremity was performed with a specific progression that utilized readily available equipment. Testing was completed at baseline and at 4, 8, and 20 weeks. The posterior shoulder endurance test was performed to assess muscular endurance. Glenohumeral internal and external rotation range of motion and strength were measured.Results:Posterior shoulder endurance improved from 30 ± 14 repetitions at baseline to 66 ± 26 at 4 weeks and 88 ± 36 at 20 weeks (P < 0.05). Glenohumeral internal rotation range of motion and the glenohumeral internal/external rotation strength ratio remained similar over the course of the program.Conclusion:Implementation of a preseason training program effectively increased shoulder muscular endurance while maintaining strength ratios and range of motion throughout the 20-week program.Clinical Relevance:This program improved a key parameter known to be associated with shoulder function and injury risk. This study describes a simple clinical tool to assess muscular endurance of the posterior shoulder.

Upper Extremity Strength Characteristics in Female Recreational Tennis Players With and Without Lateral Epicondylalgia

Descriptive, cross-sectional. To compare static strength characteristics of the upper extremity musculature in female recreational tennis players with lateral epicondylalgia to those of nonsymptomatic tennis players and a control group of women who did not play tennis. There is a paucity of research describing the relationship between lateral epicondylalgia and strength characteristics of the upper extremity musculature, despite the functional relationship between the shoulder, elbow, and wrist. Sixty-three women were recruited into 3 groups (n = 21 per group): symptomatic tennis players (STP) with lateral epicondylalgia, nonsymptomatic tennis players, and controls. Data collection was performed during a single session, during which the strength of selected muscle groups of the dominant upper extremity was measured using a combination of force transducers. Strength ratios of selected muscle groups were then calculated. The STP group reported median pain level of 3/10 on a numeric pain rating scale and a symptom duration of 16 weeks. The STP group had weaker lower trapezius strength (mean difference, -9.0 N; 95% confidence interval [CI]: -13.5, -4.4) and wrist extensor strength (-12.7 N; 95% CI: -24.4, -1.1), and a higher shoulder internal/external rotation strength ratio (0.19; 95% CI: 0.02, 0.35) and upper/lower trapezius strength ratio (1.32; 95% CI: 0.41, 2.23), compared to those of the nonsymptomatic group. Compared to the control group, the STP group demonstrated a significantly higher shoulder internal/external rotation strength ratio (0.21; 95% CI: 0.04, 0.38) and wrist flexion/extension strength ratio (0.14; 95% CI: 0.01, 0.27). In this group of recreational female tennis players, significant differences in strength and strength ratio characteristics were identified. Although the design of the study precludes establishing a cause-and-effect relationship, the results suggest further study and treatment of the muscle groups of interest.

Hip Strength and Knee Pain in High School Runners: A Prospective Study

To determine whether pre-injury hip muscle weakness is associated with the development of patellofemoral pain (PFP) in high school running athletes. Prospective cohort study. Academic institution sports medicine center. High school running athletes. Baseline hip strength of high school running athletes was assessed at the beginning of the running season. Strength testing was repeated in athletes who developed PFP. Peak hip muscle strengths and strength ratios were compared between the injured and non-injured groups. Six injuries occurred in 5 of the 98 subjects who completed the study. The baseline hip external-to-internal strength ratio was lower in injured than in uninjured subjects (P = .008). In the injured group, hip abduction and external rotation strengths decreased from pre-injury to post-injury (P = .002 and P = .01, respectively). Logistic regression analysis demonstrated that a greater baseline hip abduction strength (odds ratio = 5.35, 95% confidence interval [CI] 1.46-19.53; P < .01) and abduction-to-adduction strength ratio increased the risk of injury (odds ratio = 14.14, 95% CI 0.90-221.06; P = .05), and a greater pre-injury hip external-to-internal rotation strength ratio decreased the risk of injury (odds ratio < 0.01, 95% CI ≤ .01, 0.44; P = .02). The findings of the current study suggest that stronger pre-injury hip abductors (particularly in relation to their hip adductors) and weaker pre-injury hip external rotators (particularly in relation to their hip internal rotators) are associated with the development of PFP. In addition, persons in whom PFP develops appear to lose hip abduction and external rotation strength when compared with their pre-injury strength. Finally, a higher hip external-to-internal rotation strength ratio may protect against the development of PFP.

Comparison of Shoulder Range of Motion, Strength, and Playing Time in Uninjured High School Baseball Pitchers Who Reside in Warm- and Cold-Weather Climates

Background: There is an assumption that baseball athletes who reside in warm-weather climates experience larger magnitude adaptations in throwing shoulder motion and strength compared with their peers who reside in cold-weather climates. Hypotheses: (1) The warm-weather climate (WWC) group would exhibit more pronounced shoulder motion and strength adaptations than the cold-weather climate (CWC) group, and (2) the WWC group would participate in pitching activities for a greater proportion of the year than the CWC group, with the time spent pitching predicting throwing shoulder motion and strength in both groups. Study Design: Cross-sectional study; Level of evidence, 3. Methods: One hundred uninjured high school pitchers (50 each WWC, CWC) were recruited. Rotational shoulder motion and isometric strength were measured and participants reported the number of months per year they pitched. To identify differences between groups, t tests were performed; linear regression was used to determine the influence of pitching volume on shoulder motion and strength. Results: The WWC group pitched more months per year than athletes from the CWC group, with the number of months spent pitching negatively related to internal rotation motion and external rotation strength. The WWC group exhibited greater shoulder range of motion in all planes compared with the CWC group, as well as significantly lower external rotation strength and external/internal rotation strength ratios. There was no difference in internal rotation strength between groups, nor a difference in the magnitude of side-to-side differences for strength or motion measures. Conclusion: Athletes who reside in cold- and warm-weather climates exhibit differences in throwing shoulder motion and strength, related in part to the number of months spent participating in pitching activities. The amount of time spent participating in pitching activities and the magnitude of range of motion and strength adaptations in athletes who reside in warm-weather climates may make these athletes more susceptible to throwing-related injuries.

Muscle strength and range of movement deficits 1 year after hip resurfacing surgery using posterior approach

Purpose. The aim was to evaluate the effect of the posterior surgical approach on hip muscle strength and range of movement (ROM).Methods. Maximal isometric external and internal rotator strength of the hip muscles and bilateral leg extension strength were measured by dynamometers. Active (AROM) and passive (PROM) range of motion of the hip were measured by goniometers in 30 patients before and 3, 6 and 12 months after hip resurfacing. Postoperatively the patients were advised to return to their usual physical activities.Results. Prior to the surgery internal rotation strength was on the same level on both sides, whereas external rotation strength of the operated hip was 26% (p < 0.001) lower compared with the unoperated side. External rotation strength remained at the lowered level, but internal rotation strength of the operated hip increased over the level of the contralateral side (both p < 0.001) at 12-month follow-up leading to the imbalance in external/internal rotation strength ratio (p < 0.001). Preoperatively, all active and passive ROMs of the operated side were statistically lower than on the unoperated side (p < 0.001). ROMs of the operated hip improved significantly with the exceptions that active external rotation decreased after the operation (p < 0.001).Conclusions. The patients reported remarkable decrease in pain postoperatively. However, the surgical procedure, particularly the division of the external hip rotator muscles led to specific external rotation strength and ROM deficits. Because typical spontaneous physical activity could not restore hip function, there is a need for specific postoperative rehabilitative programs.

Rehabilitation and Functional Outcomes in Collegiate Wrestlers Following a Posterior Shoulder Stabilization Procedure

Case series. Five consecutive collegiate Division I wrestlers, with a mean age of 20.2 years (range, 18-22 years), were treated postsurgical stabilization to address posterior glenohumeral joint instability. All received physical therapy postoperatively, consisting of range-ofmotion, strengthening, and plyometrics exercises, neuromuscular re-education, and sport-specific training. Functional outcome scores using the Penn Shoulder Score questionnaire were recorded at postsurgical initial evaluation and discharge. Isometric shoulder strength, measured with a handheld dynamometer at discharge, was compared with measurements made during preseason screening. Postsurgery, upon initial physical therapy evaluation, scores on the Penn Shoulder Score questionnaire ranged from 37 to 74 out of 100. All 5 wrestlers improved with rehabilitation such that their scores at discharge ranged from 81 to 91 out of 100. Mean external rotation-internal rotation strength ratio for the involved shoulder was 73.5% (range, 55.9%-88.7%) preseason and 80.9% (range, 70.2%-104.1%) postrehabilitation. Four patients were able to return to wrestling over a period of 1 season, with no episodes of reinjury to their surgically repaired shoulder. Current research on posterior glenohumeral instability is limited, due to the relatively rare diagnosis and infrequent need for surgical intervention. Providing a structured physical therapy program following this surgical procedure appeared to have assisted in a return to full functional activities and sports. Therapy, level 4. J Orthop Sports Phys Ther 2009;39(7):550-559, Epub 24 February 2009. doi:10.2519/jospt.2009.2952.

Side dominance does not affect dynamic control strength ratios in the shoulder

Purpose: To examine the normal strength relationship between eccentric external rotation (EccER) and concentric internal rotation (ConIR) strength ratios of the shoulder in the dominant and non-dominant extremities of healthy subjects. Methods: Fourteen men and sixteen women were tested in the scapular plane using two angular velocities: 90 and 120°/s. The dependent variables were: peak torque (PT), work per repetition (W/rep), and total work (TW) ratios. Results: The EccER: ConIR ratio in a non-athletic population was significantly greater (p < 0.05) for the dominant than the non-dominant extremities for PT, W/rep, and TW. There was no significant difference in torque production between the two-isokinetic velocities. W/rep and TW ratios were significantly higher in females than in males. Although PT was not statistically significant, a similar relationship existed (p = 0.069). Conclusion: In a healthy, non-athletic population, when tested at 90 or 120°/s, the EccER is just slight greater than its ConIR counterpart in women and men alike.

Normative values of agonist-antagonist shoulder strength ratios of adults aged 20 to 78 years

Objective: To determine normative values for isometric flexion/extension, abduction/adduction, and external/internal rotation strength ratios about the shoulder and to determine if these ratios are affected by age or gender. Study Design: A cross-sectional study of 120 healthy volunteers (60 men, 60 women) aged 20 to 78 years. Setting: Orthopedic research laboratory. Methods: Flexion and extension strengths were measured isometrically using a Cybex II dynamometer at arm flexion angles of 30°, 60°, and 90°. Abduction and adduction strengths were measured at 30°, 60°, and 90° abduction. Internal and external rotation strengths were measured (1) with the arm abducted 15° and neutral external/internal rotation and (2) with the arm abducted 90° and externally rotated 30° above the transverse plane. Outcome Measures: Isometric strength ratios for flexion/ extension, abduction/adduction, and external/internal rotation. Results: No statistically significant differences in agonist/ antagonist strength ratios were found between dominant and nondominant sides or between genders. Age was associated with changes in strength ratios for measurements taken with the arm flexed or abducted 90°. Posture was found to affect strength ratios. Conclusions: These data can serve as a normative reference for clinical use.

Shoulder pain in wheelchair athletes. The role of muscle imbalance.

Shoulder rotator cuff impingement syndrome is a common and disabling problem for the wheelchair athlete. In this study we investigated the role of shoulder strength imbalance as a factor for the development of this syndrome. Nineteen paraplegic male athletes underwent clinical and isokinetic examination of both shoulders with peak torque values measured in abduction, adduction, and internal and external rotation. Twenty athletic, able-bodied men without shoulder problems were tested as controls. Ten (26%) of the paraplegic athletes had rotator cuff impingement syndrome. The results of the isokinetic testing demonstrated that 1) the paraplegics' shoulders were stronger than the controls in all directions (P < 0.05); 2) the strength ratio of abduction: adduction was higher for paraplegic athletes (P < 0.05); 3) paraplegics' shoulders with rotator cuff impingement syndrome were weaker in adduction and external and internal rotation than the paraplegic athletes without impingement syndrome (P < 0.05); and 4) paraplegics' shoulders with rotator cuff impingement syndrome had higher abduction:adduction and abduction:internal rotation strength ratios than the shoulders of paraplegics without impingement syndrome (P < 0.05). We concluded that shoulder muscle imbalance, with comparative weakness of the humeral head depressors (rotators and adductors), may be a factor in the development and perpetuation of rotator cuff impingement syndrome in wheelchair athletes.

The strength characteristics of internal and external rotator muscles in professional baseball pitchers.

The purpose of this study was to establish a data base regarding the isokinetic muscular performance characteristics of the external/internal rotator muscles of professional baseball pitchers. One hundred fifty healthy professional baseball pitchers were evaluated by use of a Biodex isokinetic dynamometer. The subjects tested had a mean age of 23.4 years and a mean body weight of 199 pounds. Isokinetic tests were performed concentrically at 180 and 300 deg/sec for both the throwing and nonthrowing shoulders. Testing procedures regarding positioning and stabilization followed established guidelines. The testing protocol and actual test repetitions were standardized for each subject. Statistical analysis was performed using the Pearson Product Moment Correlation and paired t-tests. Determination of the correlation coefficient was made at the P < 0.05 level of significance. Test results for bilateral comparison of mean peak torque for the throwing and nonthrowing shoulders indicated no statistically significant difference between the internal rotators at both test speeds, or for the external rotators at 300 deg/sec. There was a significant statistical difference at the 180 deg/sec test speed for the external rotators. The external/internal rotator strength ratio indicated a 65% ratio at 180 deg/sec and a 61% ratio at 300 deg/sec. Data were also collected for mean peak torque/body weight ratios of the throwing shoulder to establish a data base in professional throwers. This study offers clinical relevance in establishing a muscle performance profile for the professional thrower. This data base can therefore be used as criteria that should be met before an injured pitcher can be returned to throwing at the professional baseball level.

Shoulder Antagonistic Strength Ratios: A Comparison between College-Level Baseball Pitchers and Nonpitchers

The purpose of this study was to investigate the shoulder strength ratios obtained from college-level baseball pitchers and age- and sex-matched nonpitchers. Shoulder flexion/extension and externallinternal rotation strength ratios were assessed in 10 pitchers and 9 nonpitchers. Speeds selected for testing were 180 and 300 degrees /sec on the Cybex /I.@R esults indicated that both pitchers and nonpitchers generated greater peak torque values for the extensors and internal rotators than for the flexors and external rotators of the shoulder. A comparison of shoulder strength ratios between a pitcher's throwing arm and his nonthrowing arm was statistically significant (p < 0.05) for shoulder external/internal rotation at the speeds of 180 and 300 "/set. A comparison of shoulder strength ratios between pitchers and nonpitchers on the nondominant arm was not statistically significant for any of the speeds or directions tested. A comparison of the shoulder strength ratios between pitchers and nonpitchers on the dominant arm was statistically significant (p < 0.05) for all directions and speeds tested. The relationship between shoulder muscle imbalance and injury was discussed. J Orthop Sports Phys Ther 1987;8(9):451-461.