Isokinetic Scapular Muscle Performance in Overhead Athletes With and Without Impingement Symptoms

Context: Overhead activities such as throwing, tennis, or volleyball place athletes at considerable risk for overuse injuries. A relationship between scapulothoracic muscle imbalance and shoulder pain has been suggested.Objective: To compare the isokinetic muscle performance of the scapular muscles between overhead athletes with impingement symptoms and uninjured overhead athletes and to identify strength deficits in the patient population.Design: A repeated-measures analysis of variance with 1 within-subjects factor (side) and 1 between-subjects factor (group) was used to compare strength values and agonist:antagonist ratios across sides and across groups.Setting: University laboratory.Patients or Other Participants: Thirty overhead athletes with chronic shoulder impingement symptoms and 30 overhead athletes without a history of shoulder pain.Intervention(s): A linear protraction-retraction movement in the scapular plane at 2 velocities (12.2 cm/s and 36.6 cm/s).Main Outcome Measure(s): Isokinetic strength values and protraction:retraction ratios for both velocities.Results: Overhead athletes with impingement symptoms showed decreased force output:body weight at both velocities in the protractor muscles on the injured side compared with the uninjured side (-13.7% at slow velocity, -15.5% at high velocity) and compared with the control group at high velocity (-20.7%). On both sides, the patient group had significantly lower protraction:retraction ratios than the control group, measured at slow velocity (nondominant = -11%, dominant = -13.7%).Conclusions: Overhead athletes with impingement symptoms demonstrated strength deficits and muscular imbalance in the scapular muscles compared with uninjured athletes.     

Associations Among Hip and Shoulder Range of Motion and Shoulder Injury in Professional Baseball Players

Context:

The overhead throwing motion is complex, and restrictions in range of motion (ROM) at the hip may place additional demands on the shoulder that lead to injury. However, the relationship between hip and shoulder ROM in athletes with and without a history of shoulder injury is unknown.

Objective:

To (1) determine if differences exist in hip and shoulder ROM between professional baseball players with a history of shoulder injury and those with no history of shoulder injury and (2) assess relationships between hip and shoulder ROM in these players.

Design:

Cross-sectional study.

Patients or Other Participants:

Fifty-seven professional baseball players.

Main Outcome Measure(s):

Outcome measures consisted of hip extension and internal rotation, shoulder internal and external rotation, glenohumeral internal-rotation deficit, and history of shoulder injury. Differences in shoulder and hip ROM were assessed with a 1-way analysis of variance. Associations between hip and shoulder ROM were assessed with linear regression.

Results:

Nonpitchers with a history of shoulder injury had more external rotation and less internal rotation of the shoulder than nonpitchers with no history of shoulder injury. Glenohumeral internal-rotation deficit was greater in both pitchers and nonpitchers with a history of shoulder injury. The relationship between dominant hip extension and shoulder external rotation was significant for pitchers with a history of shoulder injury and nonpitchers with a history of shoulder injury.

Conclusions:

Shoulder injury may be associated with specific measures of hip and shoulder ROM, and hip extension and shoulder external rotation may be related in baseball players with a history of shoulder injury. Additional research is necessary to understand the specific mechanisms of shoulder injury in the throwing athlete.     

Recent Injury and Health-Related Quality of Life in Adolescent Athletes

Context:

Health-related quality of life (HRQOL) is a global concept that takes into account the physical, psychological, and social domains of health. Determining the extent to which injury affects HRQOL is an important aspect of rehabilitation practice, enabling comparisons of clinical outcomes across different conditions in diverse patient groups.

Objective:

To examine the extent to which a self-reported recent injury affected HRQOL in adolescent athletes using 2 generic patient self-report scales.

Design:

Cross-sectional study.

Setting:

High school classrooms and athletic training facilities.

Patients or Other Participants:

A convenience sample of uninjured (n  =  160) and injured (n  =  45) adolescent athletes.

Intervention(s):

The independent variable was injury status: uninjured versus injured. All participants completed a self-administered brief health status questionnaire and the Short Form–36 Health Survey Questionnaire (SF-36) and Pediatric Outcomes Data Collection Instrument (PODCI) in a counterbalanced manner.

Main Outcome Measure(s):

Dependent variables included 8 subscale and 2 composite scores of the SF-36 and 5 subscale scores and 1 global score of the PODCI. Group differences were assessed with the Mann-Whitney U test (P ≤ .05) and reported as median and interquartile range.

Results:

On the SF-36, the injured group demonstrated lower scores (P < .008) for physical functioning, limitations due to physical health problems, bodily pain, social functioning, and the physical composite. On the PODCI, the injured group reported lower scores (P < .01) on the pain and comfort subscale and the global score.

Conclusions:

Adolescent athletes with self-reported injuries demonstrated lower HRQOL than their uninjured peers. As expected, recent injury affected physical functioning and pain. Social functioning (on the SF-36) and global HRQOL (on the PODCI) also decreased, suggesting that injuries affected areas beyond the expected physical component of health. Clinicians need to recognize the full spectrum of negative influences that injuries may have on HRQOL in adolescent athletes.     

Subchondral Bone Radiodensity Patterns in the Glenoid Fossa of Ape and Human Scapulae

Regions of denser subchondral bone deep to a joint's articular surface indicate locations where the joint experiences relatively higher or more frequent compressive trans‐articular forces than less dense regions. Human clinically focused studies have hypothesized that regional variation of acquired with computed tomography osteoabsorptiomety (CT‐OAM), in the scapular glenoid fossa (GF) is specifically related to forces arising from everyday rotator cuff muscle function. We test this hypothesis by investigating the relationship between rotator cuff function and GF HiRD subchondral bone patterns in a broader comparative context. CT‐OAM was used on scapulae of chimpanzees, gibbons and humans to visualize HiRD subchondral bone patterns and assess regional (anterior–posterior; superior–inferior) differences in HiRD concentrations within each group. Like patterns observed in humans, ape GFs show HiRD concentrations in anterior, posterior and superior regions. Gibbons exhibit significantly larger concentrations anteriorly, probably serving as a skeletal correlate of increased subscapularis activity during humeral internal rotation during arm‐swinging locomotion. Chimpanzees exhibit relatively larger areas posteriorly (though not statistically significant), conceivably serving as a correlate of increased infraspinatus activity during humeral external rotation and retraction during knuckle‐walking. All groups show relatively larger HiRD areas superiorly, likely correlating with forceful humeral abduction (rather than adduction) during routine upper limb use across behaviors. Subchondral bone HiRD patterns in the GF appear to correspond with normal and unbalanced rotator cuff activity and force production not only in humans, but also in other primates, thereby corroborating their value in human clinical studies and functional morphology research. Anat Rec, 301:776–785, 2018. © 2017 Wiley Periodicals, Inc.     

The effect of humeral torsion on rotational range of motion in the shoulder and throwing performance

Several recent studies have found that throwing athletes typically have lower humeral torsion (retroversion) and a greater range of external rotation at the shoulder than non-athletes. How these two parameters are related is debated. This study uses data from a sample of both throwers and non-throwers to test a new model that predicts torsion values from a range of motion data. The model proposes a series of predicted regressions which can help provide new insight into the factors affecting rotational range of motion at the shoulder. Humeral torsion angles were measured from computed tomography scans collected from 25 male subjects. These values are compared to predicted torsion values for the same subjects calculated from both kinematic and goniometric range-of-motion data. Results show that humeral torsion is negatively correlated (goniometric: r = -0.409, P = 0.047; kinematic: r = -0.442, P = 0.035) with external rotational range of motion and positively correlated (goniometric: r = 0.741, P < 0.001; kinematic: r = 0.559, P = 0.006) with internal rotational range of motion. The predicted torsion values are highly correlated (goniometric: r = 0.815, P < 0.001; kinematic: r = 0.617, P = 0.006) with actual torsion values. Deviations in the data away from predicted equations highlight significant differences between high torsion and low torsion individuals that may have significant functional consequences. The method described here may be useful for non-invasively assessing the degree of torsion in studies of the evolution and biomechanics of the shoulder and arm, and for testing hypotheses about the etiology of repetitive stress injuries among athletes and others who throw frequently.     

Shoulder muscle strength in paraplegics before and after kayak ergometer training

The purpose was to investigate if shoulder muscle strength in post-rehabilitated persons with spinal cord injury (SCI) was affected by kayak ergometer training and to compare shoulder strength in persons with SCI and able-bodied persons. Ten persons with SCI (7 males and 3 females, injury levels T3–T12) performed 60 min kayak ergometer training three times a week for 10 weeks with progressively increased intensity. Maximal voluntary concentric contractions were performed during six shoulder movements: flexion and extension (range of motion 65°), abduction and adduction (65°), and external and internal rotation (60°), with an angular velocity of 30° s⁻¹. Position specific strength was assessed at three shoulder angles (at the beginning, middle and end of the range of motion) in the respective movements. Test–retests were performed for all measurements before the training and the mean intraclass correlation coefficient was 0.941 (95% CI 0.928–0.954). There was a main effect of kayak ergometer training with increased shoulder muscle strength after training in persons with SCI. The improvements were independent of shoulder movement, and occurred in the beginning and middle positions. A tendency towards lower shoulder muscle strength was observed in the SCI group compared to a matched reference group of able-bodied persons. Thus, it appears that post-rehabilitated persons with SCI have not managed to fully regain/maintain their shoulder muscle strength on a similar level as that of able-bodied persons, and are able to improve their shoulder muscle strength after a period of kayak ergometer training.