Internal Rotation Ratio Research Articles

Shoulder External Over Internal Rotation Ratio Is Related to Biomechanics in Collegiate Baseball Pitching.

Altering baseball pitching mechanics affects both performance and the risk of injury. The purpose of this study is to investigate the relationships of shoulder external over internal rotation ratio (SEIR) and other shoulder rotational properties during physical exam and biomechanics of pitching for 177 collegiate baseball pitchers. The shoulder range of motion was quantitatively measured using a custom-made wireless device. Pitching motion data were collected at 240Hz, and a custom program was created to calculate the throwing arm motion and loading during baseball pitching. Linear regression and analysis of variance tests were performed to investigate the relationships between the shoulder physical exam outcomes and throwing arm biomechanics. SEIR had significant correlations with shoulder horizontal adduction angle at foot contact, maximum shoulder external rotation angle, maximum shoulder linear velocity, and elbow angle at ball release. SEIR groups had significant differences in shoulder proximal force, adduction torque, internal rotation torque, and horizontal adduction torque, and in elbow medial force and varus torque. Glenohumeral internal rotation deficit and total rotational motion deficit had no relationships with throwing arm motions or joint loadings. Shoulder health should be monitored to improve understanding of pitching mechanics in collegiate baseball pitchers.

Efficacy of throwing exercise with TheraBand in male volleyball players with shoulder internal rotation deficit: a randomized controlled trial

BackgroundThe Glenohumeral internal-rotation deficit (GIRD) is related to the altered eccentric external-rotator (ER), the concentric internal-rotator (IR), muscle strength, and the ER: IR ratio. GIRD has been documented as a risk factor for shoulder injuries. However, few studies have investigated the effect of an exercise training on these parameters in athletes with GIRD. Therefore, the purpose of this study was to evaluate the effects of an 8-week throwing exercise with a TheraBand for retraining the rotator cuff on Electromyography (EMG) activity of selected muscles, rotator cuff muscle strength, the glenohumeral (GH) joint IR range of motion (ROM) and GH joint position sense in asymptomatic male volleyball players with GIRD.MethodsSixty male volleyball players with GIRD were randomized into either a training group or a control group. The experimental group underwent an 8-week throwing exercise with a TheraBand including 5 sessions of stretching and 3 sessions of strengthening exercises per week. The control group received an active self-exercise program. EMG (onset time and muscle activation), shoulder range of motion (ROMs), strength and GH joint position sense were all assessed pre and post trainings.ResultsThere were statistically significant within-group differences in the EMG activity of the anterior deltoid (p = 0.005), middle deltoid (p = 0.007), posterior deltoid (p = 0.004), infraspinatus (p = 0.001) and supraspinatus (p = 0.001) muscles, IR ROM (p = 0.001), rotator cuff muscle strength ratio (p = 0.001), and GH joint position sense (p = 0.033) in the experimental group. A 2 × 2 analysis of variance with a mixed model design and independent and paired t-tests were used for statistical analysis.ConclusionsThrowing exercise with a TheraBand improved shoulder muscle activation, IR ROM, rotator cuff muscle strength ratio and GH joint position sense in participants with GIRD. These findings may improve the treatment of GIRD in a clinical setting. Although the results are significant, further studies should follow up the long-term effects of the Throwing exercise with a TheraBand on GIRD.Trial registrationCurrent Controlled Trials using the UMIN-RCT website with ID number of, UMIN000038416 “Retrospectively registered” at 2019/10/29.

The association between genu recurvatum angle and the strength of the hip and knee muscles in standing workers.

Increased genu recurvatum (GR) angle is a risk factor for knee injury. Identification of factors causing GR is important for the prevention and rehabilitation of GR. Few studies have investigated the association between muscle strength and GR. To examine the association between GR angle and hip and knee muscle strength in standing workersMETHODS:The participants in this study were 110 healthy volunteers (59 male, 51 female) who performed standing work in a theme park. The GR angle, muscle strength, and strength ratio of the lower extremities were measured to determine their associations with GR. The GR angle was measured using a Smart KEMA motion sensor, and muscle strength was assessed using a Smart KEMA strength sensor. Stepwise multiple regression models were used to investigate which muscles contributed most to the extent of the GR angle. Stepwise multiple regression analysis showed that the decreased hip external rotator to hip internal rotator ratio, increased knee extensor to knee flexor ratio, and young age were associated with an increased GR angle. Many factors are known to increase the GR angle. However, this study investigated the roles of only hip and knee muscle strength. The results suggest that muscle strength ratios are more important than the weakness of any muscle.

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.

Profiling Shoulder Strength in Competitive Surfers.

The shoulder region has the highest incidence of acute injuries in the sport of surfing. Little is known about the strength profile at the shoulder in a surfing cohort. The primary aim of this study was to establish the reliability of a rotator cuff strength testing procedure for surfers with a secondary aim of providing a profile of internal and external rotation strength in a competitive surfing cohort. Shoulder internal rotation and external rotation isometric strength was measured using a hand-held dynamometer in 13 competitive surfers. Intra-class coefficient values ranged from 0.97 to 0.98 for intra-rater reliability and were lower for inter-rater reliability ranging from 0.80 to 0.91. Internal rotation strength was greater than external rotation strength bilaterally (dominant, p = 0.007, non-dominant, p < 0.001). No differences (p < 0.79) were found in internal rotation strength between the dominant and non-dominant arms. External rotation strength was weaker on the non-dominant arm compared with the dominant arm (p < 0.02). The non-dominant arm external rotation to internal rotation ratio (0.82 ± 0.15) was lower (p = 0.025) than the dominant arm (0.88 ± 0.14). The current procedure is reliable with the same clinician, and results indicate musculature asymmetry specific to the external rotators.

The association between menarche, intensity of training and passive joint ROM in young pre-professional female dancers: A longitudinal follow-up study

ObjectivesTo determine the association between the status of menarche (yes/no), the intensity of training and the potential to improve passive joint range of motion (ROM) over a 12-month period of dance training. DesignProspective cohort study. SettingDance studio. ParticipantsFifty-nine female dancers aged 12.8 ± 0.5. Main outcome measuresThe dancers were asked about their dance intensity and screened for anthropometric parameters and passive joint ROM in Grades 7 and 8. ResultsAlong the 12 months of dance training, we found significantly increased ankle-foot en-pointe, hip abduction, and hip external rotation (ER); significantly decreased hip internal rotation (IR); and significant increased hip ER:IR ratio. In Grade 7, 26 dancers (44.1%) reached menarche (Yes menarche); in Grade 8 an additional 23 dancers (39.0%) reached menarche (No/Yes menarche); and 10 dancers (16.9%) had not reached menarche (No menarche). MANOVA (mixed models) with repeated measures to compare joint ROM between the three menarche groups (Yes; No/Yes; No), with h/week dance practice as a co-variant, showed that hip ER, ankle-foot en-pointe, and ER:IR were significantly correlated with h/week in all three menarche groups. ConclusionsMost passive joint ROM can be improved over 12 months of dancing around the age onset of menarche. H/week of dance practice is a main factor contributing to improved hip ER, ankle-foot en-pointe and ER/IR ratio.

Desempenho muscular isocinético dos ombros em atletas de rúgbi

*** Isokinetic muscle performance of shoulders in rugby athletes ***AIMS: To verify the existence of shoulder external and internal rotator muscle asymmetries in male amateur rugby athletes.METHODS: Isokinetic evaluations of male amateur rugby athletes were accessed from the database of the Institute for Sports Medicine and Applied Sciences in Human Movement of Universidade de Caxias do Sul (IME-UCS). Shoulders evaluated were included in the study, whereas those cases without a free and informed consent form signed prior to the test were excluded. The isokinetic dynamometer was used in a concentric-concentric mode for the shoulder external and internal rotators at angular velocities of 60°/s and 180°/s. The peak torque and the external to internal rotator ratio were analyzed. Student’s t test and a significance level of &lt;0.05 were used to verify the existence of asymmetries between the two sides of the same individual.RESULTS: Data from 12 male athletes were analyzed. Regarding the peak torque at the angular velocity of 60º/s, the mean muscle strength values of the dominant limb were significantly higher when compared to non-dominant limb: external rotators, 43.35±4.72 Nm for the dominant limb vs 38.92±4.22 Nm for the non-dominant limb (p=0.0012); internal rotators, 65.58±11.88 Nm for the dominant limb vs 61.69±11.98 Nm for the non-dominant limb (p=0.0021). At 180º/s, the mean values of the non-dominant limb tended to be lower when compared to the dominant limb, without statistical significance. Regarding the mean values of the external to internal rotator ratio, no significant differences were found at any of the angular velocities analyzed.CONCLUSIONS: Amateur rugby athletes showed lower muscle strength of the non-dominant limb when compared to the dominant limb in the peak torque measurements. This difference was not found in other studies with rugby athletes, and we believe that this result is justified by the lack of more frequent and adequate training of these amateur athletes.

Acute effects of scapular Kinesio Taping® on shoulder rotator strength, ROM and acromiohumeral distance in asymptomatic overhead athletes.

There is limited information in the literature that shows whether scapular taping has an effect on the acromiohumeral distance (AHD) and shoulder functions. The aim of this study was to investigate the acute effects of scapular Kinesio Taping® on shoulder internal rotation (IR) and external rotation (ER) strength, IR and ER range of motion (ROM) and AHD in asymptomatic overhead athletes. Forty-one volleyball athletes (24 men, 17 women; mean age: 16.1±1.5 years, body mass: 66.5±9.6 kg, body height: 179.6±8.4 cm, Body Mass Index: 20.5±2.3 kg/m2, time participating in overhead sports activity: 6.2±1.4 h/week, experience in sport: 4.1±2.4 years) were included in this study. Shoulder IR and ER ROM, total rotation ROM, AHD, shoulder isometric IR and ER strength and ER:IR strength ratio of the dominant side were tested before and after taping. Scapular taping increased the shoulder IR (P<0.001) and total ROM (P<0.001), AHD (P<0.001), shoulder IR (P=0.002) and ER (P=0.006) strength. ER ROM and ER:IR ratio did not change after taping (P=0.26, P=0.98, respectively). The results of this study suggest that scapular taping could be an effective method for enhancing the acromiohumeral distance, shoulder rotator strength and range of motion. Therefore, scapular taping could be recommended for not only in the asymptomatic athletes' shoulder exercise training but also in the prevention of subacromial impingement syndrome.

Anatomical glenohumeral internal rotation deficit and symmetric rotational strength in male and female young beach volleyball players

Beach volleyball is a sport with a high demand of shoulder structures that may lead to adaptations in range of motion (ROM) and strength like in other overhead sports. Despite of these possible alterations, no study evaluated the shoulder adaptations in young beach volleyball athletes. The aim of this study was to compare the bilateral ROM and rotation strength in the shoulders of young beach volleyball players. Goniometric passive shoulder ROM of motion and isometric rotational strength were evaluated in 19 male and 14 female asymptomatic athletes. External and internal ROM, total rotation motion, glenohumeral internal rotation deficit (GIRD), external rotation and internal rotation strength, bilateral deficits and external rotation to internal rotation ratio were measured. The statistical analysis included paired Student’s t-test and analysis of variance with repeated measures. Significantly lower dominant GIRD was found in both groups (p<0.05), but only 6 athletes presented pathological GIRD. For strength variables, no significant differences for external or internal rotation were evident. Young beach volleyball athletes present symmetric rotational strength and shoulder ROM rotational adaptations that can be considered as anatomical. These results indicate that young practitioners of beach volleyball are subject to moderate adaptations compared to those reported for other overhead sports.

The Effect of Glenohumeral Internal-Rotation Deficit on Functional Rotator-Strength Ratio in Adolescent Overhead Athletes.

Glenohumeral (GH) internal-rotation deficit (GIRD) and lower eccentric external-rotator (ER) to concentric internal-rotator (IR) strength (ER:IR) ratio have been documented as risk factors for shoulder injuries, but there is no information on whether GIRD has an adverse effect on ER:IR ratio in adolescent overhead athletes. The aim of this study was to investigate the effects of GIRD on functional ER:IR ratio of the adolescent overhead athletes. Cross-sectional study. University research laboratory. 52 adolescent overhead athletes. To determine GIRD, the range of GH IR and ER motion was measured with a digital inclinometer. An isokinetic dynamometer was used to assess eccentric and concentric IR and ER muscle strength of the dominant and nondominant shoulders. One-way ANCOVA where sport type was set as a covariate was used to analyze the difference between athletes with and without GIRD. After standardized examinations of all shoulders, the athletes were divided into 2 groups, shoulders with (n = 27) and without GIRD (n = 25). There was a significant difference between groups in functional ER:IR ratio (P < .001). Athletes with GIRD had lower ER:IR ratio (0.56) than athletes without GIRD (0.83). As GIRD has an adverse effect on functional ratio of the shoulder-rotator muscles, interventions for adolescent overhead athletes should include improving GH-rotation range of motion.

Shoulder rotator strength and torque steadiness in athletes with anterior shoulder instability or SLAP lesion

To investigate shoulder rotator strength and steadiness in athletes with anterior instability and superior labrum anterior posterior (SLAP) lesion. Cross-sectional laboratory study. Athletes with anterior shoulder instability (instability group, n=10) and a SLAP lesion (SLAP group, n=10) were compared with healthy athletes matched by age, anthropometrics and sport (control group for shoulder instability, n=10 and control group for SLAP, n=10). Torque steadiness was evaluated with three 10s submaximal isometric contractions (35% of peak torque) with the arm at 90° of shoulder abduction and 90° of external rotation. The mean isometric torque, standard deviation and coefficient of variation were measured from the steadiness trials. To evaluate shoulder rotator strength, concentric isokinetic tests (90°/s, 180°/s) were performed at the 90-90° position and peak torque to body mass and shoulder external to internal rotation ratio variables were analyzed. The variables were tested with the instability and control groups with respect to shoulder instability and between the SLAP and control groups for SLAP lesion using the Mann-Whitney test. The SLAP group presented a higher coefficient of variation than the SLAP control group (p=0.003). Regarding shoulder strength, the internal and external shoulder rotators were weaker in the instability group than in the instability control group (p<0.05). Athletes with anterior shoulder instability presented shoulder rotation weakness, while athletes with a SLAP lesion showed higher torque fluctuation during internal rotation. These results indicate that there are different alterations to strength and sensory motor control in each condition.

등속성 검사를 통한 견관절 전방 불안정 환자와 정상인의 회전력 비교

Objective: It has been expected that patient with posttraumatic recurrent anterior shoulder dislocation might have limited daily life activity because of pain and apprehension of dislocation. But there have been only a small number of investigations regarding the rotator strength in this patient. The aim of this study is to find the characteristics about rotator strength of patient with posttraumatic recurrent anterior shoulder dislocation using an isokinetic testing. Method: We enrolled thirteen patients with posttraumatic recurrent anterior shoulder dislocation and fifteen sex, age-matched healthy nonathletic subjects in this controlled study. All participants were male and there were no significant differences between the two groups in age, height, weight, BMI. Isokinetic internal rotator and external rotator strength was evaluated with a Biodex Isokinetic Testing machine (Biodex Medical Systems, Shirley, NY, USA), tests were performed at 60 deg/sec and 180 deg/sec for both sides. Peak torque normalized to body weight, external rotator to internal rotator ratio, total work and fatigue were calculated for each angular velocity. The association between internal rotator and external rotator strength and shoulder instability was analyzed by comparisons with a control group. Results: Any notable differences could not be found between the two groups given all data from no symptomatic left shoulder. There were no significant differences between the two groups statistically in internal rotation strength of right shoulder. However, there has been a tendency that at all angular velocities, external rotator peak torque to body weight, total work and external rotator to internal rotator ratio were significantly lower in the anterior instability group than the control group at all angular velocities. There was no substantial difference between those groups with respect to the fatigue of external rotator and internal rotator in our study. Conclusion: The prominent characteristics of posttraumatic recurrent anterior shoulder dislocation are external rotator weakness and loss of balance with external rotator and internal rotator. Therefore selective training using this information rotator might be helpful in conservative treatment and rehabilitation.

Rotator Cuff Strength in Recurrent Anterior Shoulder Instability

Although rotator-cuff muscle contraction plays an important role in stabilizing the glenohumeral joint, little is known about the role of these muscles in the pathophysiology of recurrent anterior instability. We intended to analyze the association between isokinetic internal rotator and external rotator muscle strength and glenohumeral joint instability in patients with recurrent anterior instability that was not previously treated surgically. We enrolled thirty-seven patients with unilateral recurrent anterior posttraumatic shoulder dislocation and eleven healthy nonathletic subjects in this controlled study. The association between internal rotator and external rotator strength and shoulder instability was analyzed by side-to-side comparisons and comparisons with a control group. Isokinetic internal rotator and external rotator strength was evaluated with a Con-Trex dynamometer, with the subject seated and the shoulder abducted 45° in the scapular plane. Tests were performed at 180°/s, 120°/s, and 60°/s in concentric mode for both sides. Peak torque normalized to body weight and external rotator to internal rotator ratio were calculated for each angular velocity. Clinical and isokinetic evaluation was done by the same rehabilitation physician. The association between shoulder instability and internal rotator and external rotator strength was associated with side-to-side differences (p < 0.05). Compared with a control group, strength values were lower on the pathological shoulder side of the patients with shoulder instability than on the healthy contralateral shoulder of control subjects at 180°/s and 120°/s (p < 0.05). The side-to-side differences were increased when the nondominant upper-extremity side was involved and were decreased when the dominant side was involved. There was no association between glenohumeral joint instability and external rotator to internal rotator ratio. Internal rotator and external rotator weakness was associated with recurrent anterior instability, and side-to-side differences depended on the side of hand dominance. Use of a control group may help in the analysis of the influence of constraints on shoulder strength. Further prospective studies are necessary to determine whether the weakness is a cause or an effect of the instability.

Are Rearfoot Motion Parameters Normally Distributed?

Averaged rearfoot motion profiles and parameters in running gait have been reported in many past experiments however, small sample sizes have limited the interpretation of their estimates. If these parameters are not normally distributed, then we must use nonparametric statistics, which lack the generalize ability of inferential statistics. PURPOSE: The purpose of this study was to provide rearfoot motion estimates by studying a larger sample population than is usual in rearfoot motion studies and to determine if rear foot parameters are normally distributed. METHODS: Kinematics of the foot and leg were measured in 25 healthy male (age 20.9 ± 4.0) and 25 healthy female subjects (age 21.0 ± 3.2). Data were collected on the right side in 3D at 240 Hz. Marker triads were placed on the leg and calcaneus. Subjects wore running sandals and ran on a treadmill at 3.5 m/s. Joint angles were calculated with a Cardan XYZ sequence of rotations then smoothed and time scaled. Means and 95% confidence intervals were calculated for: inversion angle at heel strike (IN_HS); maximum eversion during stance (Max_EV); inversion/eversion excursion during stance (ROM); time to maximum eversion (TTMaxEv); eversion to tibial internal rotation ratio (EV/TIR); eversion/tibial internal rotation ratio (EV/TIR); and eversion/tibial internal rotation relative to the lab coordinate system (EV/TIR_lab). A Shapiro-Wilk test was used to test for the normality of each variable. RESULTS: CONCLUSION: One of the criteria in using inferential statistics to analyze rearfoot motion is that the scores are normally distributed. In general, it was apparent that the distributions of rearfoot parameters for males, females and combined were normal.Table

Upper Limb Force Parameters In Tennis, Swimming And Basketball Elite Portuguese Female Athletes (16 - 18)

PURPOSE: To compare upper limb force in elite young women athletes from three different sports: tennis players (TP), swimmers (SW) and basketball players (BP). METHODS: 29 young females (16 – 18 years old) participated in the study, divided in three groups: TP (n=9), SW (n=10) and BP (n=9). All participants were athletes of the Portuguese national teams. Concentric strength measures for both arms were performed on a Biodex isokinetic dynamometer at 60 and 180°/s. The subjects were seated with the arm positioned in 45° abduction in the scapular plane and elbow flexed to 90°. Isometric maximum force and the maximum rate of force development were measured in a bench press type of exercise. To examine between-group differences we used the ANOVA and a-posteriori test with a level of significance of p<0.05. RESULTS: The peak torque of arm internal rotation (IR) was significantly (p<.05) higher in both arms in the SW compared with TP and BP, for the velocity of 60°/s. At 180°/s the SW presented significantly (p<.00) higher internal rotation than the BP but no differences were found between SW and TP. The peak torque of the external rotation (ER) force was significantly (p<.01) lower in the TP than in the SW and BP for both arms and at both velocities. A significant (p<.03) higher ER:IR ratio was found in both arms and velocities for the BP (dominant arm − 78% and 76% at 60°/s and 180°/s; nondominant arm − 70% and 69%), than for the TP (dominant arm − 53% and 44%; nondominant arm − 58% and 46%) and SW (dominant arm − 59% and 55%; nondominant arm − 56% and 52%). In the bench press movement the SW presented significant (p<.00) higher maximal force then the TP and BP. No differences were found in the maximal rate of force production. CONCLUSIONS: Based in these force parameters, the SW were the strongest in the upper limb. The TP were the weakest athletes in the arm ER force. The recommended ER:IR ratio to provide muscular balance ranges between 66 and 75% (Ellenbecker & Roetert, 2003). The BP presented the better RE:RI ratio. This is caused by the repetition of fast internal rotation arm movements in SW and TP and represents a potential source for shoulder imbalance and injury. REFERENCES: Ellenbecker, T., & Roetert, E. (2003). J Sc Med Sp, 6: 63–70.

Factors Correlated with Volleyball Spike Velocity

Background Spike effectiveness represents a determining element in volleyball. To compete at a high level, the player must, in particular, produce a spike characterized by a high ball velocity. Hypothesis Some muscular and physical features could influence ball velocity during the volleyball spike. Study Design Descriptive laboratory study. Methods A total of 19 male volleyball players from the 2 highest Belgian national divisions underwent an isokinetic assessment of the dominant shoulder and elbow. Ball velocity performance (radar gun) during a spike test, morphological feature, and jump capacity (ergo jump) of the player were measured. We tested the relationship between the isokinetic parameters or physical features and field performances represented by spike velocity. We also compared first-division and second-division player data. Results Spike velocity correlated significantly with strength performance of the dominant shoulder (internal rotators) and of the dominant elbow (flexors and extensors) in the concentric mode. Negative correlations were established with the concentric external rotator on internal rotator ratio at 400 deg/s and with the mixed ratio (external rotator at 60 deg/s in the eccentric mode on internal rotator at 240 deg/s in the concentric mode). Positive correlations appeared with both the volleyball players’ jump capacity and body mass index. First-division players differed from second-division players by higher ball velocity and increased jump capacity. Conclusion Some specific strength and physical characteristics correlated significantly with spike performance in high-level volleyball practice. Clinical Relevance Our results could provide useful information for training management and propose some reflections on injury prevention.

Lower Extremity Kinematic and Kinetic Differences in Runners with High and Low Arches

High- and low-arched feet have long been thought to function differently. The purpose of this study was to investigate the relationship between arch structure and lower extremity mechanics in runners with extreme pes planus and pes cavus. It was hypothesized that low-arched individuals would exhibit an increased rearfoot eversion excursion, eversion/tibial internal rotation ratio, and increased angular velocity in rearfoot eversion when compared to high-arched runners. In addition, it was hypothesized that high-arched runners would exhibit greater vertical loading rates. Twenty high-arched and 20 low-arched runners with histories of running-related injuries were included in this study. Low-arched runners were found to have increased rearfoot eversion excursion, eversion to tibial internal rotation ratio, and rearfoot eversion velocity. High-arched runners had increased vertical loading rate when compared to low-arched runners. These results suggest that arch structure is associated with specific lower extremity kinematics and kinetics. Differences in these parameters may subsequently lead to differences in injury patterns in high-arched and low-arched runners.

Concentric and Eccentric Isokinetic Rotator Cuff Ratios in Skilled Tennis Players

Kevin Kennedy, PT, ATC* • David W. Altchek, MDt Irving V. Glick, MD=I= Hospital for Special Surgery, New York --------------------. -------------------The purpose of this study was to compare the concentric and eccentric strength of the internal and external rotators in skilled tennis players. Isokinetic testing of 62 male and female tennis players (Volvo levels 4-5 through 6-0) was performed on a LIDO Active Isokinetic System. Tests were conducted bilaterally for concentric internal and external rotation at 60 deg/sec, and for concentric and eccentric external rotators at 150 deg/sec. The concentric isokinetic testing of the dominant side at 60 deg/sec showed an external rotation to internal rotation ratio of 0.67 for average work per repetition. On the nondominant side, the ratio was 0.77. This difference represents a statistically significant difference in the work of the internal rotators in the playing arm. When tested at 150 deg/sec concentrically and eccentrically for the external rotators, it was found that the eccentric to concentric ratio was 1.46 for the average work per repetition on the dominant side. On the nondominant side, the ratio was 1.19. This difference represents a statistically significant difference in the work performed by the external rotators eccentrically. It was also determined that on the playing arm the external rotators' torque ratio, eccentric to concentric, was 1.43. From our data it was concluded that when measured eccentrically, the external rotators of the dominant arm were significantly stronger than those on the nondominant arm.