Craig A. Wassinger

Asymmetric resting scapular posture in healthy overhead athletes.

CONTEXT Observation of the scapular posture is one of the most important components of the physical examination in overhead athletes. Postural asymmetry is typically considered to be associated with injuries. However, asymmetry in the overhead athletes scapula may be normal due to the dominant use of the limb. OBJECTIVE To quantify the differences in resting scapular posture between the dominant and nondominant sides in 3 groups of healthy overhead athletes (baseball pitchers, volleyball players, and tennis players) using an electromagnetic tracking device. DESIGN Cross-sectional design. SETTING University-based biomechanics laboratory. PATIENTS OR OTHER PARTICIPANTS A total of 43 players participated, including 15 baseball pitchers, 15 volleyball players, and 13 tennis players. All participants were healthy college-aged men. INTERVENTION(S) Bilateral 3-dimensional scapular kinematics with the arm at rest were measured using an electromagnetic tracking device. MAIN OUTCOME MEASURE(S) Bilateral scapular position and orientation were measured. Between-groups and between-sides differences in each variable were analyzed using separate analyses of variance. RESULTS In tennis players, the scapula was more protracted on the dominant side than on the nondominant side (P < .05). In all overhead athletes, the dominant-side scapula was more internally rotated (P = .001) and anteriorly tilted (P = .001) than the nondominant-side scapula was. CONCLUSIONS The dominant-side scapula of the overhead athletes was more internally rotated and anteriorly tilted than the nondominant-side scapula. The dominant-side scapula of the tennis players was more protracted than that on the nondominant side. Clinicians evaluating overhead athletes need to recognize that scapular posture asymmetry in unilateral overhead athletes may be normal. Our results emphasize the importance of the baseline evaluation in this population in order to accurately assess pathologic change in bilateral scapular positions and orientations after injury.

Reliability, Precision, Accuracy, and Validity of Posterior Shoulder Tightness Assessment in Overhead Athletes

Background Posterior shoulder tightness with subsequent loss of humeral internal rotation range of motion has been linked to upper extremity lesions in overhead athletes. A valid clinical assessment is necessary to accurately identify posterior shoulder tightness as a contributor to injury. Purpose To describe a modified supine assessment of posterior shoulder tightness by establishing the reliability, precision, clinical accuracy, and validity of the assessment. Study Design Cohort study (diagnosis); Level of evidence, 2. Methods Intrasession, intersession, and intertester reliability and precision were established by comparing the commonly used side-lying assessment of posterior shoulder tightness and the described modified supine assessment. Clinical accuracy of both methods was obtained using an electromagnetic tracking device to track humeral and scapular motion. Construct validity was established by identifying posterior shoulder tightness in a group of overhead athletes (baseball pitchers and tennis players) reported in the literature to have limited humeral internal rotation and posterior shoulder tightness. Results The side-lying intrasession intraclass correlation coeffecient (standard error of measurement), intersession intraclass correlation coeffecient (standard error of measurement), and intertester intraclass correlation coeffecient (standard error of measurement) were 0.83 cm (0.9), 0.42 cm (1.7), and 0.69 cm (1.4), respectively. The supine intrasession intraclass correlation coeffecient (standard error of measurement), intersession intraclass correlation coeffecient (standard error of measurement), and intertester intraclass correlation coeffecient (standard error of measurement) were 0.91° (1.1°), 0.75° (1.8°), and 0.94° (1.8°), respectively. In side-lying, the clinical accuracy expected was 0.9 ± 0.6 cm of error while, when measured supine, it was 3.5° ± 2.8° of error. Both assessments resulted in minimal scapular protraction (~3.5°). Between groups, baseball pitchers and tennis players had significantly less internal rotation range of motion (P < .0001) and greater posterior shoulder tightness (P = .004) when measured in supine, but not in side-lying (P = .312). Conclusion Both methods resulted in good clinician accuracy and precision, suggesting that both can be performed accurately. The supine method can be assessed more reliably than side-lying between both sessions and testers. Clinical Relevance Clinicians may want to consider use of the supine method given the higher reliability, validity, and similar precision and clinical accuracy.

Diagnostic accuracy of scapular physical examination tests for shoulder disorders: a systematic review

Objective To systematically review and critique the evidence regarding the diagnostic accuracy of physical examination tests for the scapula in patients with shoulder disorders. Methods A systematic, computerised literature search of PubMED, EMBASE, CINAHL and the Cochrane Library databases (from database inception through January 2012) using keywords related to diagnostic accuracy of physical examination tests of the scapula. The Quality Assessment of Diagnostic Accuracy Studies tool was used to critique the quality of each paper. Results Eight articles met the inclusion criteria; three were considered to be of high quality. Of the three high-quality studies, two were in reference to a ‘diagnosis’ of shoulder pain. Only one high-quality article referenced specific shoulder pathology of acromioclavicular dislocation with reported sensitivity of 71% and 41% for the scapular dyskinesis and SICK scapula test, respectively. Conclusions Overall, no physical examination test of the scapula was found to be useful in differentially diagnosing pathologies of the shoulder.

Three-Dimensional Scapular and Clavicular Kinematics and Scapular Muscle Activity During Retraction Exercises

STUDY DESIGN Controlled laboratory study. OBJECTIVES To describe and compare scapular and clavicular kinematics and muscle activity during 6 retraction exercises in young healthy adults (mean +/- SD age, 23.2 +/- 2.4 years). BACKGROUND Based on the association between shoulder injuries and scapular/clavicular movement, muscle activity during various exercises that target muscles surrounding the scapula have been investigated. However, the scapular and clavicular movements occurring during these exercises remain uninvestigated. Evaluation of the scapular and clavicular kinematics in addition to muscle activity provides additional information that allow clinicians to select exercises that best meet the patients needs. METHODS Three-dimensional scapular and clavicular kinematics and scapular muscle activity data were collected while the participants performed 6 scapular retraction exercises. One-way repeated-measures ANOVA and post hoc analyses were used to determine differences in scapular/clavicular kinematics and activation levels of the upper, middle, and lower trapezius and serratus anterior muscles occurring during the exercises. RESULTS The general pattern of the kinematics observed during all retraction exercises was scapular external rotation, scapular upward rotation, scapular posterior tilting, clavicular retraction, and clavicular depression. However, the exercises resulted in varying amounts of scapular movement and muscle activity. CONCLUSION Clinicians can select appropriate exercises for their patients based on their need to strengthen specific retractor muscles and to improve specific scapular and clavicular movement patterns, pre-existing conditions, and available range of motion.

The effects of shoulder injury on kinaesthesia : A systematic review and meta-analysis

The aim of this systematic review was to synthesize the evidence for changes for proprioceptive variables consisting of movement and position sense in participants with glenohumeral musculoskeletal disorders. Five databases were searched until 13th August 2013. Methodological quality was assessed and meta-analyses were performed for active and passive joint reposition sense (AJPS and PJPS) and movement sense, determined with threshold to detection of passive motion (TTDPM). The search yielded 17 studies, four of which were classified as having high methodological quality, seven as moderate and six as low quality. For participants with post-traumatic glenohumeral instability, pooled findings indicate moderate evidence for higher TTDPM for involved shoulders compared to control groups and the contralateral uninvolved side, indicating decreased movement sense. For AJPS and PJPS there was moderate to limited evidence for significant increased errors for involved compared to uninvovled shoulders, but not when compared to the control groups. Limited evidence was found for decreased AJPS acuity for patients with chronic rotator cuff pain and for patients with unspecified shoulder pain compared to healthy controls. Movement sense is most likely to be impaired after shoulder injury involving post-traumatic instability when compared to the contralateral shoulder and to controls, while deficits for AJPS and PJPS are more likely to be evident compared to the contralateral shoulder in participants with glenohumeral musculoskeletal disorders.

Clinical Measurement of Scapular Upward Rotation in Response to Acute Subacromial Pain

STUDY DESIGN Block-counterbalanced, repeated-measures crossover study. OBJECTIVES To assess scapular upward rotation positional adaptations to experimentally induced subacromial pain. BACKGROUND Existing subacromial pathology is often related to altered scapular kinematics during humeral elevation, such as decreased upward rotation and posterior tilting. These changes have the potential to limit subacromial space and mechanically impinge subacromial structures. Yet, it is unknown whether these changes are the cause or result of injury and what the acute effects of subacromial pain on scapular upward rotation may be. METHODS Subacromial pain was induced via hypertonic saline injection in 20 participants, aged 18 to 31 years. Scapular upward rotation was measured with a digital inclinometer at rest and at 30°, 60°, 90°, and 120° of humeral elevation during a painful condition and a pain-free condition. Repeated-measures analyses of variance were conducted for scapular upward rotation position, based on condition (pain or control) and humeral position. Post hoc testing was conducted with paired t tests as appropriate. RESULTS Scapular upward rotation during the pain condition was significantly increased (range of average increase, 3.5°-7.7°) compared to the control condition at all angles of humeral elevation tested. CONCLUSION Acute subacromial pain elicited an increase in scapular upward rotation at all angles of humeral elevation tested. This adaptation to acute experimental pain may provide protective compensation to subacromial structures during humeral elevation.

The efficacy of incorporating partial squats in maximal strength training.

Abstract Bazyler, CD, Sato, K, Wassinger, CA, Lamont, HS, and Stone, MH. The efficacy of incorporating partial squats in maximal strength training. J Strength Cond Res 28(11): 3024–3032, 2014—The purpose of our study was to examine the effects of 2 different training methods on dynamic and isometric measures of maximal strength. Seventeen recreationally trained men (1 repetition maximum [1RM] squat: 146.9 ± 22.4 kg) were assigned to 2 groups: full range of motion (ROM) squat (F) and full ROM with partial ROM squat (FP) for the 7-week training intervention. Repeated measures analysis of variance revealed that there was a statistically significant group-by-time interaction for impulse scaled at 50, 90, and 250 milliseconds at 90° of knee flexion and rate of force development at 200 milliseconds with 120° of knee flexion (p ⩽ 0.05). There was also a statistically significant time effect (p ⩽ 0.05) for the 1RM squat, 1RM partial squat, isometric squat peak force allometrically scaled (IPFa) 90°, IPFa 120°, and impulse allometrically scaled at 50, 90, 200, and 250 milliseconds at 90° and 120° of knee flexion. Additionally, the FP group achieved statistically larger relative training intensities (%1RM) during the final 3 weeks of training (p ⩽ 0.05). There was a trend for FP to improve over F in 1RM squat (+3.1%, d = 0.53 vs. 0.32), 1RM partial squat (+4.7%, d = 0.95 vs. 0.69), IPFa 120° (+5.7%, d = 0.52 vs. 0.12), and impulse scaled at 50, 90, 200, and 250 milliseconds at 90° (+6.3 to 13.2%, d = 0.50–1.01 vs. 0.30–0.57) and 120° (+3.4 to 16.8%, d = 0.45–1.11 vs. 0.08–0.37). These larger effect sizes in the FP group can likely be explained their ability to train at larger relative training intensities during the final 3 weeks of training resulting in superior training adaptations. Our findings suggest that partial ROM squats in conjunction with full ROM squats may be an effective training method for improving maximal strength and early force-time curve characteristics in men with previous strength training experience. Practically, partial squats may be beneficial for strength and power athletes during a strength-speed mesocycle while peaking for competition.

The role of experimentally-induced subacromial pain on shoulder strength and throwing accuracy

Shoulder injuries often comprise two separate yet related components, structural tissue damage and pain. The role of each of these components on shoulder function is difficult to ascertain. Experimental pain models allow the assessment of consequences of localized pain when applied to healthy individuals. By understanding the role of pain on shoulder function, clinicians will be able to more efficiently assess and treat shoulder injuries. The objective of the study was to evaluate the role of experimentally-induced sub-acromial pain on shoulder isokinetic rotational strength and throwing accuracy. This was a block counterbalanced, crossover, repeated measures study design utilizing 20 individuals without self-reported shoulder or cervical pathology. Shoulder function was measured with and without experimental pain injection (2 mL of 5% hypertonic saline) in the sub-acromial space. Functional tasks consisted of shoulder rotational strength utilizing isokinetic testing and throwing accuracy via the functional throwing performance index. The hypertonic saline induced moderate pain levels in all participants (4.3-5.1/10). Normalized shoulder internal (t = 3.76, p = 0.001) and external (t = 3.12, p = 0.006) rotation strength were both diminished in the painful condition compared to the pain free condition. Throwing accuracy was also reduced while the participants experienced pain (t = 3.99, p = 0.001). Moderate levels of experimental shoulder pain were sufficient to negatively influence shoulder strength and throwing accuracy in participants without shoulder pathology.

Scapulohumeral kinematic assessment of the forward kayak stroke in experienced whitewater kayakers

By understanding the normal humeral and scapular kinematics during the kayak stroke, inferences about the relationship of kayaking technique and shoulder injury may be established. The purpose of this study was to describe scapular and humeral kinematics and to compare dominant versus non-dominant symmetry in healthy whitewater kayakers performing the forward stroke. Twenty-five competent whitewater kayakers (mean age: 34.1 ± 9.4 years, mean height: 1.768 ± 0.093 m, mean mass: 78.2 ± 13.0 kg) underwent humeral and scapular kinematic assessment, using an electromagnetic tracking device, while kayaking on a kayak ergometer. Paired t-tests were used to determine symmetry. Scapular and humeral kinematic means and standard deviations at six time points during the kayak stroke were described. Scapular and humeral kinematics were shown to be similar upon bilateral comparison. The greatest potential for injury during the forward stroke may be at thrust paddle shaft vertical when the humerus is maximally elevated in internal rotation and adduction as subacromial structures may be mechanically impinged. The relationship between scapulohumeral kinematics related to injury at other time points are also described.

Electromyographic response of shoulder muscles to acute experimental subacromial pain

This study investigated effects of experimentally-induced subacromial pain, induced via hypertonic saline injection, on shoulder muscles activity. Electromyographic activity of 20 healthy participants was assessed for humeral elevation and descent for the control and experimental pain conditions, using fine wire electrodes for subscapularis and supraspinatus and surface electrodes for middle deltoid, upper trapezius, lower trapezius, infraspinatus, and serratus anterior. Normalized mean amplitudes were analyzed for each muscle for four phases for elevation and descent, respectively. Repeated measures analysis of variances (ANOVAs) were used to determine differences between muscle activity in the control and experimental condition for the four phases of elevation and descent. Differences for mean normalized amplitudes were not significant during humeral elevation. Increased activity was found for the pain condition for serratus anterior and middle deltoid during the first (120-90°) and third (60-30°) parts and decreased activity for infraspinatus in the second half of descent (60-0°). No significant differences were found during descent for upper and lower trapezius, subscapularis and supraspinatus. While increased serratus anterior activity during 60-30° of descent may be protective, increased middle deltoid and decreased infraspinatus activity during the same range may threaten subacromial tissues in that range. Overall the changes in muscle activation were individual specific, particularly during the concentric elevation phase.