Spine & Sports Institute

Am J Sports Med January 2009 vol. 37 no. 1 149-155

Background Several studies have reported that physical loading related to competitive sports activities is associated with lumbar intervertebral disk degeneration. However, the association between types of sports activities and disk degeneration has not been clarified.

Hypothesis The frequencies of disk degeneration may vary with the competitive sport because of the different postures and actions specific to each sport.

Study Design Cross-sectional study (prevalence); Level of evidence, 3.

Methods Study participants were 308 well-trained university athletes (baseball players, basketball players, kendo competitors, runners, soccer players, swimmers) and 71 nonathlete university students (reference group). Disk degeneration was evaluated using T2-weighted magnetic resonance imaging. A self-reported questionnaire concerning low back pain was also conducted.

Results The proportions of the participants who had disk degeneration among the baseball players (odds ratio, 3.23) and the swimmers (odds ratio, 2.95) were significantly higher than among the nonathletes using logistic regression analysis. When all patients were grouped together, the association between lifetime experience of low back pain and participants with disk degeneration was significant, and a linear association between the degree of severest low back pain experienced and participants with disk degeneration, analyzed by a Cochran-Mantel-Haenszel test, was also significant.

Conclusion Continuous competitive baseball and swimming activities during youth may be associated with disk degeneration. Furthermore, the study indicates that the experience of severe low back pain might be a predictor of disk degeneration in youth. The authors hope that preventive measures and management to protect against disk degeneration and low back pain in athletes will be established by further studies based on these results.

Background High-intensity repetitive athletic activities may predispose the brachial plexus to repetitive stretch, compression, and subsequent injury, although painless shoulder weakness is a rare event.

Purpose The physical examination and electrodiagnostic findings in a series of United States Navy special warfare trainees who presented with acute painless shoulder weakness are presented, along with subsequent treatment and return-to-duty timeline.

Study Design Case series; Level of evidence, 4.

Methods From August 2005 to August 2006, a total of 11 of 212 (5%) Navy Basic Underwater Demolition School trainees were identified with acute onset (<3 weeks) painless shoulder weakness without any prior shoulder injury. In all shoulders, symptoms began during a telephone pole lift-carry drill. All trainees underwent serial examinations, electrodiagnostic testing, and a comprehensive rehabilitation program.

Results Physical examination revealed universal weakness in flexion and abduction and electrodiagnostic studies confirmed injury to the C5-6 area of the brachial plexus (axillary, suprascapular, and musculocutaneous). All 11 patients were removed from training and started on a physical therapy program until functional recovery at a mean of 21 weeks after onset of symptoms (range, 12–24). All 11 resumed military activities; however, only 6 completed the Navy Basic Underwater Demolition School program.

Conclusion In physically intense training or athletic environments, injuries to the upper brachial plexus may present with various forms of upper extremity dysfunction, including painless shoulder weakness. This information provides insight into a potentially debilitating shoulder problem and offers guidance on future training principles.

Background The incidence of shoulder and elbow injuries in adolescent baseball players is rapidly increasing. One leading theory about this increase is that breaking pitches (such as the curveball) place increased moments on the dominant arm and thereby increase the risk of injury.

Hypothesis There is no difference in the moments at the shoulder and elbow between fastball and curveball pitches in adolescent baseball pitchers.

Study Design Controlled laboratory study.

Methods Thirty‐three adolescent baseball pitchers with a minimum of 2 years of pitching experience underwent 3‐dimensional motion analysis using reflective markers aligned to bony landmarks. After a warm‐up, pitchers threw either a fastball or curveball, randomly assigned, from a portable pitching mound until 3 appropriate trials were collected for each pitch technique. Kinematic and kinetic data for the upper extremities, lower extremities, thorax, and pelvis were collected and computed for both pitch types. Statistical analysis included both the paired sample t test and mixed model regression.

Results There were lower moments on the shoulder and elbow when throwing a curveball versus when throwing a fastball. As expected, speed for the 2 pitches differed: fastball, 65.8 ± 4.8 mph; and curveball, 57.7 ± 6.2 mph (P < .001). Maximal gle‐nohumeral internal rotation moment for the fastball was significantly higher than for the curveball (59.8 ± 16.5 N·m vs 53.9 ± 15.5 N·m; P < .0001). Similarly, the maximum varus elbow moment for the fastball was significantly higher than for the curveball (59.6 ± 16.3 N·m vs 54.1 ± 16.1 N·m; P < .001). The wrist flexor moment was greater in the fastball, 8.3 ± 3.6 N·m, than in the curveball, 7.8 ± 3.6 N·m (P < .001), but the wrist ulnar moment was greater in the curveball, 4.9 ± 2.0 N·m, than in the fastball, 3.2 ± 1.5 N·m (P < .001). Relatively minor motion differences were noted at the shoulder and elbow throughout the pitching motion, while significant differences were seen in forearm and wrist motion. The forearm remained more supinated at each point in the pitching cycle for the curveball but had less overall range of motion (62° ± 20°) than with the fastball (69° ± 17°) (P < .001), and the difference in the forearm pronation and supination moment between the pitches was not significant (P = .104 for pronation and P = .447 for supination). The wrist remained in greater extension during the fastball from foot contact through ball release but did not have significantly different total sagittal range of motion (53° ± 11°) when compared with the curveball (54° ± 15°) (P = .91).

Conclusion In general, the moments on the shoulder and elbow were less when throwing a curveball than when throwing a fastball. In each comparison, the fastball demonstrated higher moments for each individual pitcher for both joints.

Clinical Relevance The findings based on the kinematic and kinetic data in this study suggest that the rising incidence of shoulder and elbow injuries in pitchers may not be caused by the curveball mechanics. Further evaluation of adolescent and adult baseball pitchers is warranted to help determine and subsequently reduce the risk of injury.

W. Ben Kibler, MD*, Aaron D. Sciascia, MS, ATC*,†, Timothy L. Uhl, PhD, PT, ATC‡, Nishin Tambay, MD§, and Thomas Cunningham, MS‡

Am J Sports Med September 2008 36:1789-1798

Abstract

Background: Restoration of control of dynamic scapular motion by specific activation of the serratus anterior and lower trapezius muscles is an important part of functional rehabilitation. This study evaluated activation of those muscles in specific exercises.

Hypothesis: Specific exercises will activate key scapular-stabilizing muscles in clinically significant amplitudes and patterns.

Study Design: Controlled laboratory study.

Methods: Muscle activation amplitudes and patterns were evaluated in the serratus anterior, upper trapezius, lower trapezius, anterior deltoid, and posterior deltoid muscles with electromyography in symptomatic (n = 18) and asymptomatic (n = 21) subjects as they executed the low row, inferior glide, lawnmower, and robbery exercises.

Results: There were no significant differences in muscle activation amplitude between groups. Muscle activation was moderate across all of the exercises and varied slightly with the specific exercise. The serratus anterior and lower trapezius were activated between 15% and 30% in all exercises. Upper trapezius activation was high (21%–36%) in the dynamic exercises (lawnmower and robbery). Serratus anterior was activated first in the low row and last in the lawnmower and robbery. The upper trapezius and lower trapezius were activated first in the lawnmower and robbery.

Conclusion: These specific exercises activate key scapular-stabilizing muscles at amplitudes that are known to increase muscle strength.

Clinical Relevance: These exercises can be used as part of a comprehensive rehabilitation program for restoration of shoulder function. They activate the serratus anterior and lower trapezius—key muscles in dynamic shoulder control—while variably activating the upper trapezius. Activation patterns depended on scapular position resulting in variability of amplitude and activation sequencing between exercises. Inferior glide and low row can be performed early in rehabilitation because of their limited range of motion, while lawnmower and robbery, which require larger movements, can be instituted later in the sequence.

Ann M. Cools, PT, PhD†,*, Vincent Dewitte, PT†, Frederick Lanszweert, PT†, Dries Notebaert, PT†, Arne Roets, MPSS‡, Barbara Soetens, PhD‡, Barbara Cagnie, PT, PhD†, and Erik E. Witvrouw, PT, PhD†

Am J Sports Med October 2007 35:1744-1751

Abstract

ackground: Strengthening exercises for the scapular muscles are used in the treatment of scapulothoracic dysfunction related to shoulder injury. In view of the intermuscular and intramuscular imbalances often established in these patients, exercises promoting lower trapezius (LT), middle trapezius (MT), and serratus anterior (SA) activation with minimal activity in the upper trapezius (UT) are recommended.

Hypothesis: Of 12 commonly used trapezius strengthening exercises, a selection can be performed for muscle balance rehabilitation, based on a low UT/LT, UT/MT, or UT/SA muscle ratio.

Study Design: Controlled laboratory study.

Methods: Electromyographic activity of the 3 trapezius parts and the SA was measured in 45 healthy subjects performing 12 commonly described scapular exercises, using surface electromyography.

Results: For each intramuscular trapezius ratio (UT/LT, UT/MT), 3 exercises were selected for restoration of muscle balance. The exercises side-lying external rotation, side-lying forward flexion, prone horizontal abduction with external rotation, and prone extension were found to be the most appropriate for intramuscular trapezius muscle balance rehabilitation. For the UT/SA ratio, none of the exercises met the criteria for optimal intermuscular balance restoration.

Conclusion: In cases of trapezius muscle imbalance, some exercises are preferable over others because of their low UT/LT and UT/MT ratios.

Clinical Relevance: In the selection of rehabilitation exercises, the clinician should have a preference for exercises with high activation of the LT and MT and low activity of the UT.

An Intervention Study in Premier League Female Soccer

Robert Kraemer, MD and Karsten Knobloch, PhD, MD*

Am J Sports Med July 2009 39:1384-1393

Abstract

Background: A soccer-specific balance training has been shown to decrease injury incidence of the anterior cruciate ligament and ankle sprains in randomized controlled trials. However, hamstring injuries and tendinopathy remain significant issues in soccer.

Hypothesis: Proprioceptive training can reduce the incidence of hamstring muscle injuries and tendinopathy in elite soccer. There is a dose-effect relationship between balance training duration and injury incidence.

Study Design: Cohort study; Level of evidence, 3.

Methods: Twenty-four elite female soccer players (body mass index, 21.7 ± 1.2; age, 21 ± 4 years) of a German premier league soccer team were prospectively included. Starting in January 2004, an additional soccer-specific proprioceptive multistation training was initiated over 3 years. Injury data/1000 hours of exposure with documentation of all occurred injuries, detailed training, and match exposure data as well as time loss data were 100% complete.

Results: At the end of the 3-year proprioceptive balance training intervention, noncontact hamstring injury rates were reduced from 22.4 to 8.2/1000 hours (P = .021), patellar tendinopathy from 3.0 to 1.0/1000 hours (P = .022), and Achilles tendinopathy from 1.5 to 0.0/1000 hours (P = .035). There was no effect of balance training on contact injuries. Mean time loss of all assessed injuries significantly decreased from 14.4 days during the control period to 1.5 days during intervention periods (P = .003). The more minutes of balance training performed, the lower the rate of overall injuries (r = −0.185, P = .001), hamstring injuries (r = −0.267, P = .003), patellar tendinopathy (r = −0.398, P = .02), and gastrocnemius strains (r = −0.342, P = .002).

Conclusion: Soccer-specific balance training (protective balancing) can reduce noncontact hamstring injuries and patellar and Achilles tendinopathy. A dose-effect relationship between duration of balance training and injury incidence is evident. A proprioceptive training program reduced the rehabilitation time in noncontact injuries, which warrants further investigation.

Background: Immobilization of the shoulder in external rotation has been shown to reduce the risk of recurrence after traumatic anteroinferior shoulder dislocation. It remains unclear how duration of immobilization affects labral coaptation.

Hypothesis: Immobilization of the shoulder in 30° of external rotation for 5 weeks allows better coaptation of the anteroinferior labrum than does an immobilization period of 3 weeks.

Study Design: Cohort study; Level of evidence, 2.

Methods: Twenty-two patients with traumatic anteroinferior dislocation of the glenohumeral joint were included in this study. Patients were divided into 2 groups. Group 1 consisted of the initial 11 patients (mean age, 37.4 years) immobilized for 3 weeks; group 2 consisted of the subsequent 11 patients (mean age, 29.7 years) immobilized for 5 weeks in 30° of external rotation. With use of magnetic resonance imaging, displacement and separation of the glenoid labrum and anterior joint effusion were assessed in different arm positions (internal rotation, neutral rotation, 30° of external rotation, maximum external rotation) within 3 days, 3 weeks, and 5 weeks after reduction.

Results: Displacement and separation of the labrum and anterior joint effusion were significantly less, particularly with maximum external rotation compared with neutral and internal rotation, during the acute magnetic resonance imaging evaluation in both groups (P < .05). No statistically significant differences were found in all parameters comparing internal rotation with neutral rotation, 30° of external rotation, and maximum external rotation in both groups after 5 weeks (P > .05). No statistically significant differences were found between both groups comparing the results of the measured variables during the acute, 3-week, and 5-week magnetic resonance imaging examinations (P > .05).

Conclusion: Immobilization of the shoulder in 30° of external rotation seems to allow a similar coaptation of the glenoid labrum, regardless of duration of immobilization (3 vs 5 weeks). Clinical trials are needed to evaluate the effect of these results on recurrence rates. The optimum position of immobilization in external rotation has yet to be determined.