Development of an In-Vitro Passive and Active Motion Simulator for the Investigation of Shoulder Function and Kinematics

Injuries and degenerative diseases of the shoulder are common and may relate to the joint’s complex biomechanics, which rely primarily on soft tissues to achieve stability. Despite the prevalence of these disorders, there is little information about their effects on the biomechanics of the shoulder, and a lack of evidence with which to guide clinical practice. Insight into these disorders and their treatments can be gained through in-vitro biomechanical experiments where the achieved physiologic accuracy and repeatability directly influence their efficacy and impact. This work’s rationale was that developing a simulator with greater physiologic accuracy and testing capabilities would improve the quantification of biomechanical parameters. This dissertation describes the development and validation of a simulator capable of performing passive assessments, which use experimenter manipulation, and active assessments – produced through muscle loading. Respectively, these allow the assessment of functional parameters such as stability, and kinematic/kinetic parameters including joint loading. The passive functionality enables specimen motion to be precisely controlled through independent manipulation of each rotational degree of freedom (DOF). Compared to unassisted manipulation, the system improved accuracy and repeatability of positioning the specimen (by 205% & 163%, respectively), decreased variation in DOF that are to remain constant (by 6.8°), and improved achievement of predefined endpoints (by 21%). Additionally, implementing a scapular rotation mechanism improved the physiologic accuracy of simulation. This enabled the clarification of the effect of secondary musculature on shoulder function, and the comparison of two competing clinical reconstructive procedures for shoulder instability. This was the first shoulder system to use real time kinematic feedback and PID control to produce active motion, which achieved unmatched accuracy ( These developments can be a powerful tool for increasing our understanding of the shoulder and also to provide information which can assist surgeons and improve patient outcomes

Low threshold CW Nc laser oscillator at 1060 nm study

A broad range of characteristics of neodymium/yag lasers were investigated. With Nd:YVO4 crystals, CW 1.06 mu lasers were operated with thresholds a factor of 2 lower than Nd:YAG and with greater slope efficiencies. Thus, the first step in the development of new oscillators suitable for application in high data rate laser communication systems which surpass the present performance of the Nd:YAG laser has been successfully demonstrated

Prognosis and Movement Patterns in Patients After Rotator Cuff Repair

Rotator cuff repairs are done in patients who failed to achieve functional improvement with conservative management for rotator cuff tears. This thesis focuses on prognostic factors that predict outcomes after rotator cuff repair (RCR) and change in functional range of motion (ROM) and muscle endurance before and after RCR. A meta-analysis was performed to statistically analyze all available evidence in the literature concerning prognostic factors that determine outcome after RCR. Based on this study, several factors were identified that had significant and moderate effects on outcomes after RCR. Two prospective studies were conducted to analyze change in functional ROM and muscle endurance after RCR. The first study followed patients pre-op, 3 and 6 months after RCR. Patients performed 2 trials of 5 activities selected from Disabilities of Arm, Shoulder and Hand questionnaire. The activities were captured using 2D video motion system and analysed using Dartfish software. This study showed excellent intra-rater reliability while using the 2D video analysis system with improvement in ROM during all activities when compared before and after surgery with significant improvement in 2 activities when compared at different time points. A prospective study to evaluate muscle endurance at 6 months after surgery was done using an endurance protocol on the Biodex system and compared with age- and gender-matched controls. Results of this study indicated that changes in muscle performances as measured by average isokinetic torque and total work before and after the protocol did not indicate muscle fatigue in patients after RCR and in the control group. We also analysed the psychometric properties of Simple shoulder test (SST) using the Rasch model to assess its fit to the model and to examine the stability of the findings at different time points. Our results indicated that a number of properties of SST were supported and it appeared to be robust when tested against the Rasch model. Local dependency between light and heavy objects being lifted overhead fits with their conceptual overlap. Unless corrected some gender bias may exist on the lifting item

The 2.5 m Telescope of the Sloan Digital Sky Survey

We describe the design, construction, and performance of the Sloan Digital Sky Survey Telescope located at Apache Point Observatory. The telescope is a modified two-corrector Ritchey-Chretien design which has a 2.5-m, f/2.25 primary, a 1.08-m secondary, a Gascoigne astigmatism corrector, and one of a pair of interchangeable highly aspheric correctors near the focal focal plane, one for imaging and the other for spectroscopy. The final focal ratio is f/5. The telescope is instrumented by a wide-area, multiband CCD camera and a pair of fiber-fed double spectrographs. Novel features of the telescope include: (1) A 3 degree diameter (0.65 m) focal plane that has excellent image quality and small geometrical distortions over a wide wavelength range (3000 to 10,600 Angstroms) in the imaging mode, and good image quality combined with very small lateral and longitudinal color errors in the spectroscopic mode. The unusual requirement of very low distortion is set by the demands of time-delay-and-integrate (TDI) imaging; (2) Very high precision motion to support open loop TDI observations; and (3) A unique wind baffle/enclosure construction to maximize image quality and minimize construction costs. The telescope had first light in May 1998 and began regular survey operations in 2000.Comment: 87 pages, 27 figures. AJ (in press, April 2006

A Rotating Aperture Mask for Small Telescopes

Observing the dynamic interaction between stars and their close stellar neighbors is key to establishing the stars’ orbits, masses, and other properties. Our ability to visually discriminate nearby stars is limited by the power of our telescopes, posing a challenge to astronomers at small observatories that contribute to binary star surveys. Masks placed at the telescope aperture promise to augment the resolving power of telescopes of all sizes, but many of these masks must be manually and repetitively reoriented about the optical axis to achieve their full benefits. This paper introduces a design concept for a mask rotation mechanism that can be adapted to telescopes of different types and proportions, focusing on an implementation for a Celestron C11 Schmidt–Cassegrain optical tube assembly. Mask concepts were first evaluated using diffraction simulation programs, later manufactured, and finally tested on close double stars using a C11. An electronic rotation mechanism was designed, produced, and evaluated. Results show that applying a properly shaped and oriented mask to a C11 enhances contrast in images of double star systems relative to images captured with the unmasked telescope, and they show that the rotation mechanism accurately and repeatably places masks at target orientations with minimal manual effort. Detail drawings of the mask rotation mechanism and code for the software interface are included

Lateral versus posterior approach to shoulder injection in patients with subacromial impingement syndrome: A mixed methods study

Objectives: To determine the effectiveness of lateral approach to subacromial injection compared to posterior approach for the treatment of subacromial impingement syndrome (SAIS); and to establish the experiences of SAIS patients receiving these injections associated with better clinical outcomes. Design: This study used a mixed methods approach that combines a pragmatic randomised control trial to investigate which injection approach is better and a semi-structured qualitative interview to investigate the experiences of SAIS patients receiving these injections. Settings: Out-patients community musculoskeletal service Sample: 80 patients with SAIS for the randomised control study and 20 participants for the semi-structured qualitative interview. Interventions: The Intervention group received a single subacromial injection with a 21-gauge Green needle with a 40 mg/ml of Kenalog and a 4 ml 1% of Lidocaine through a lateral approach. The Control group received an identical treatment except that the location was by a posterior approach. Outcome measures: Difference in improvements in the overall patient reported outcome measures (PROMs) and shoulder pain and disability index score (SPADI) at 8 and 12 weeks follow-up between the two groups. Results: A moderate but statistically and clinically significant difference in improvement in day-time pain (mean change score) occurred in favour of the lateral group (mean = 3.7) compared with the posterior group (mean = 2.3) between week 0 to 8 (1.4 points [95% CI 0.3 to 2.6, p = 0.018]). However, there were no statistically significant differences between the groups in night-time pain, shoulder function and SPADI scores. There was a statistically and clinically significant difference (p = 0.001) within the groups for all clinical outcomes between week 0 to 8 and between week 0 and 12. This was confirmed by participants from the semi-structured interviews which were conducted 12 weeks after the injection. Conclusion: There were no real significant differences in the treatments; however, both forms of treatment were associated with significant improvement in shoulder pain, function and disability. This was confirmed by participants from the semi-structured interviews, who felt that they improved not only because of the effect of the cortisone injection, but also because of other factors such as education about their treatment, exercise information, the experience and skills of the injecting clinicians, access to treatment as well as good customer service

Prehabilitation for the management of rotator cuff surgery

Rotator cuff tears are a common cause of shoulder pain in the general community. Approximately one-third of patients with rotator cuff tears proceed to surgery following the failure of conservative treatments such as physiotherapy, non-steroidal anti- inflammatory drugs, opioid analgesics, and cortisone injections. However, rotator cuff tears continue to develop over time, and the burden of illness for patients awaiting rotator cuff repair is substantial, resulting in loss of strength, functional status, and poor quality of life. This dissertation proposes a three-stage approach for the management of rotator tears in patients awaiting surgery, which includes an accurate and reliable evaluation of shoulder range of motion (ROM) and strength, a pre-operative intervention to improve function and quality of life, and an appraisal of potential prognostic factors that can lead to better future clinical outcomes. Therefore, the organisation of this thesis is divided into three sections covering shoulder assessment, intervention, and prognosis. Chapter 1 introduces the concept of prehabilitation, a rapid systematic review, evidence gaps in the literature, and the rationale for shoulder prehabilitation. Prehabilitation is defined as enhancing a patient's functional ability before surgery to improve clinical outcomes following surgery. The rapid systematic review included only high-quality studies based on the National Health and Medical Research Council (Australia) evidence guidelines and the Physiotherapy Evidence Database (PEDro) rating scale. Only pre-operative exercise intervention studies for surgical knee and hip populations were identified. To date, no studies have investigated the efficacy of prehabilitation for patients scheduled for shoulder surgery. This finding necessitated a review of the considerable body of research on rotator cuff tears. Chapter 2 provides a synthesis of the current literature regarding shoulder anatomy, biomechanics of the rotator cuff, epidemiology, aetiology and classification of rotator cuff tears, shoulder assessment methods, an overview of management options, evidence for post-operative rehabilitation, and prognostic factors and potential predictors of outcome associated with rotator cuff surgery. Chapter 3 presents a published study examining the intra- and inter-rater reliability of a variety of testing protocols to measure ROM and strength in healthy participants. The objective measurement of ROM and strength is an integral part of the physical examination of patients with rotator cuff tears and is vital in quantifying improvement after conservative or surgical intervention. Correctly evaluating and interpreting objective shoulder measurements informs the clinical reasoning underlying treatment. Since pre- operative ROM and strength are potentially modifiable predictors for rotator cuff repair success, a precise assessment using reliable instruments and testing methods is essential. The outcomes of this study supported the selection of assessment methods for a randomised controlled trial (Chapter 7) on shoulder prehabilitation. Chapter 4 presents a published systematic review and meta-analysis on the reliability of the Kinect and ambulatory motion-tracking devices to measure shoulder ROM. According to our reliability study findings in Chapter 3, existing methods for evaluating shoulder ROM are less reliable. Emerging inertial sensor technologies and optical markerless motion-tracking systems are valid alternatives to standard ROM assessment methods. However, reliability must also be established before this technology can be used routinely in clinical settings. Chapter 5 presents a published validity and reliability study on the HumanTrak system to measure shoulder ROM in healthy subjects. Based on our findings in Chapter 4, we evaluated the clinical potential of using a movement analysis system that combines inertial sensors with the Microsoft Kinect (HumanTrak) to measure shoulder ROM reliably and accurately. Chapter 6 is a systematic review and meta-analysis of prehabilitation for the management of orthopaedic surgery. The initial rapid systematic review in Chapter 1 only identified orthopaedic prehabilitation programmes for patients undergoing lower limb joint arthroplasty, anterior cruciate ligament reconstruction, and spinal surgery. Given the growing research and clinical adoption of prehabilitation over the past decade, we undertook an updated and more comprehensive systematic review to identify and critically appraise the content and reporting of prehabilitation programmes for all orthopaedic surgeries. Exercise therapy is commonly first line treatment for older patients with non-traumatic rotator cuff tears. Despite growing evidence that exercise therapy and surgery can achieve comparable clinical outcomes, there is a paucity of high-quality studies on the impact of pre-operative exercise or education for patients awaiting rotator cuff surgery. Hence, the main aim of this thesis is to investigate the efficacy of a combined pre-operative exercise and education programme on function and quality of life before and after rotator cuff surgery. Chapter 7 is a randomised control trial (RCT) investigating whether the addition of a pre-operative exercise and education programme to usual care for patients awaiting rotator cuff surgery is more effective than usual care alone. Fifty patients with unilateral rotator cuff tears received either an 8-week shoulder exercise and education prehabilitation (SPrEE) programme or usual care (UC). The SPrEE programme compared to UC resulted in superior and statistically significant improvements in the primary outcomes of SPADI, WORC and SF-36 in the pre-operative phase. The SPrEE program was not more effective than UC alone in improving primary outcomes at 3-, 6- or 12 month follow-up timepoints. There were no statistically significant between-group differences in SPrEE and UC secondary outcomes for surgical or non-surgical patients. Chapter 8 investigated any correlations between pre-operative magnetic resonance imaging (MRI) characteristics and patient-reported outcome measures for patients who underwent rotator cuff repair or no surgery and received either prehabilitation or usual care in the RCT (Chapter 7). Prognosis-based prehabilitation can effectively identify patients who will derive the greatest benefit. Chapter 9 summarises thesis findings, strengths, and directions for future research to optimise function and quality of life prior to rotator cuff surgery

Modifications in Early Rehabilitation Protocol after Rotator Cuff Repair : EMG Studies

La déchirure de la coiffe des rotateurs est une des causes les plus fréquentes de douleur et de dysfonctionnement de l'épaule. La réparation chirurgicale est couramment réalisée chez les patients symptomatiques et de nombreux efforts ont été faits pour améliorer les techniques chirurgicales. Cependant, le taux de re-déchirure est encore élevé ce qui affecte les stratégies de réhabilitation post-opératoire. Les recommandations post-chirurgicales doivent trouver un équilibre optimal entre le repos total afin de protéger le tendon réparé et les activités préconisées afin de restaurer l'amplitude articulaire et la force musculaire. Après une réparation de la coiffe, l'épaule est le plus souvent immobilisée grâce à une écharpe ou une orthèse. Cependant, cette immobilisation limite aussi la mobilité du coude et du poignet. Cette période qui peut durer de 4 à 6 semaines où seuls des mouvements passifs peuvent être réalisés. Ensuite, les patients sont incités à réaliser les exercices actifs assistés et des exercices actifs dans toute la mobilité articulaire pour récupérer respectivement l’amplitude complète de mouvement actif et se préparer aux exercices de résistance réalisés dans la phase suivante de la réadaptation. L’analyse électromyographique des muscles de l'épaule a fourni des évidences scientifiques pour la recommandation de beaucoup d'exercices de réadaptation au cours de cette période. Les activités sollicitant les muscles de la coiffe des rotateurs à moins de 20% de leur activation maximale volontaire sont considérés sécuritaires pour les premières phases de la réhabilitation. À partir de ce concept, l'objectif de cette thèse a été d'évaluer des activités musculaires de l'épaule pendant des mouvements et exercices qui peuvent théoriquement être effectués au cours des premières phases de la réhabilitation. Les trois questions principales de cette thèse sont : 1) Est-ce que la mobilisation du coude et du poignet produisent une grande activité des muscles de la coiffe? 2) Est-ce que les exercices de renforcement musculaire du bras, de l’avant-bras et du torse produisent une grande activité dans les muscles de la coiffe? 3) Au cours d'élévations actives du bras, est-ce que le plan d'élévation affecte l'activité de la coiffe des rotateurs? Dans notre première étude, nous avons évalué 15 muscles de l'épaule chez 14 sujets sains par électromyographie de surface et intramusculaire. Nos résultats ont montré qu’avec une orthèse d’épaule, les mouvements du coude et du poignet et même quelques exercices de renforcement impliquant ces deux articulations, activent de manière sécuritaire les muscles de ii la coiffe. Nous avons également introduit des tâches de la vie quotidienne qui peuvent être effectuées en toute sécurité pendant la période d'immobilisation. Ces résultats peuvent aider à modifier la conception d'orthèses de l’épaule. Dans notre deuxième étude, nous avons montré que l'adduction du bras réalisée contre une mousse à faible densité, positionnée pour remplacer le triangle d’une orthèse, produit des activations des muscles de la coiffe sécuritaires. Dans notre troisième étude, nous avons évalué l'électromyographie des muscles de l’épaule pendant les tâches d'élévation du bras chez 8 patients symptomatiques avec la déchirure de coiffe des rotateurs. Nous avons constaté que l'activité du supra-épineux était significativement plus élevée pendant l’abduction que pendant la scaption et la flexion. Ce résultat suggère une séquence de plan d’élévation active pendant la rééducation. Les résultats présentés dans cette thèse, suggèrent quelques modifications dans les protocoles de réadaptation de l’épaule pendant les 12 premières semaines après la réparation de la coiffe. Ces suggestions fournissent également des évidences scientifiques pour la production d'orthèses plus dynamiques et fonctionnelles à l’articulation de l’épaule.Rotator cuff tear is one of the most common causes of shoulder pain and dysfunction. The operative repair has been widely performed for symptomatic patients and many efforts have been done to improve the surgical techniques. However, the re-tear rate is still high and this affects post-repair rehabilitation strategies. Post-surgical care should balance between the restriction imposed to protect the repaired tendon and the activities prescribed to restore range of motion and muscle strength. Frequently, early after rotator cuff repair, shoulder is immobilized in a sling or abduction orthosis, but this immobilization includes elbow and wrist joints as well. In this period that may last 4-6 weeks, only passive range of motion exercises are performed. After removing the immobilizer, patients are encouraged to do active assisted and active range of motion exercises respectively to regain the full active range of motion and be prepared for the resistance exercises in the following phase of rehabilitation. Electromyography of shoulder muscles has provided scientific basis for many of rehabilitation exercises during this period. Anecdotally, the activities of less than 20% of the maximal voluntary contraction of rotator cuff muscles are considered safe for the first phases of rehabilitation after rotator cuff repair. Using this concept, the aim of this dissertation is to evaluate the activity of shoulder musculature during some movements and exercises that can theoretically be performed during the early phases of rehabilitation. Three main questions of this thesis are: 1) Do elbow and wrist mobilizations highly activate rotator cuff muscles? 2) Do some resistance exercises of arm, forearm and chest muscles produce high activity in rotator cuff muscles? 3) During active arm elevation, does the plane of elevation affect rotator cuff activity? In our first study, we evaluated 15 shoulder muscles in 14 healthy subjects with both surface and indwelling EMG. Our results showed that while wearing a shoulder orthosis, elbow and wrist movements and even some resistance training involving these two joints, would minimally activate the rotator cuff muscles and can be considered safe. We also introduced some daily living tasks that can be performed safely during immobilization period. These findings may help to modify the design of current shoulder orthoses. In the second study, we also showed that resisted arm adduction against a low-density foam that replaced the hard wedge of orthosis would not highly activate the cuff muscles. In our final study, we evaluated the EMG of shoulder musculature during arm elevation tasks in 8 symptomatic patients with rotator cuff tears. We found that supraspinatus activity during arm elevation is significantly higher in abduction plane than in scaption and flexion planes in patients with rotator cuff tears. This suggested a plane sequences for active range of motion exercises during rehabilitation. The findings that are presented in this dissertation, suggest some modifications in the rehabilitation protocols during the first 12 weeks after rotator cuff repair. These suggestions also provide a scientific basis for producing more dynamic and functional shoulder orthoses

A combined in vivo and in vitro approach to assess supraspinatus activation and tissue responses to arm elevation demands

Rotator cuff degeneration affects a large portion of the human population, yet knowledge surrounding which loading scenarios allow transition from healthy to diseased states remains largely unresolved. Mechanistic progression of rotator cuff pathology often originates in the supraspinatus before cascading to other tissues, leading to substantial degeneration. Posture, loading and repetitive motions are known risk factors that exacerbate shoulder injury progression. This suggests a causal relationship between specific upper extremity task scenarios and degenerative rotator cuff loading. This thesis intentionally explored regional activations of the supraspinatus and accompanying tendon loading across a range of postures. The global objective was to evaluate how postural and task intensity differences alter tissue-level mechanical parameters in both in vivo muscular activation and in vitro tangent stiffness, hysteresis and optical stretch ratios. These findings combine in vivo muscular activation and physiologically relevant in vitro mechanical testing results through novel methods to better understand supraspinatus loading. Three experimental studies provided the means to achieve this global objective. In Vivo Examination of Supraspinatus Activation: The purposes of this study were 1) to document the interplay of anterior and posterior supraspinatus activations and 2) to describe the influences of posture and hand loads on anterior and posterior supraspinatus activations. Forty participants completed arm elevations in seven planes of elevation with three hand loads that were normalized to the individual’s maximal elevation force. Indwelling electromyography was collected from the anterior and posterior regions of supraspinatus. Hand load and elevation angle interacted to affect the anterior region activation in most planes of elevation by up to 41% of maximal activation, but these changes were less influential for the posterior portion. Activation patterns between the two regions suggest different functional roles of the supraspinatus portions; consistent levels of activation in the posterior supraspinatus may indicate this region is primarily a glenohumeral stabilizer, while the larger anterior region acts to achieve glenohumeral motion. This work represents the most comprehensive concurrent evaluation of these supraspinatus regions over a large set of planes of elevation, hand loads and humeral elevations, providing more holistic descriptions of supraspinatus activation in a critical arm movement. Comparing Surface Electromyography of Supraspinatus to Anterior and Posterior Indwelling Recordings: The purpose of this study was to compare anterior and posterior supraspinatus indwelling electromyography responses to a surface supraspinatus signal across a range of arm postures in order to develop relationships between these two recording methods. Forty participants completed arm elevations with altering hand loads and planes of elevation at a fixed cadence. Indwelling electromyography of the anterior and posterior supraspinatus as well as a surface recording of supraspinatus were collected. Bivariate regressions of anterior and posterior indwelling electrodes relative to the bipolar surface electrodes were used to determine relationships between these signals throughout the range of these humeral elevations. Differences between these predictions were modulated by plane of elevation, elevation angle, load intensity and sex of the participant, but no interactions existed. Surface signals underestimated indwelling activation recordings at low elevation angles, then overestimated as humeral elevation angle increased. Surface recordings underestimated indwelling signals by up to 15% in unloaded conditions, while overestimating the posterior region by up to 17% at the highest hand load intensity. In addition, surface signals overestimated posterior supraspinatus indwelling activity by 21%. This work greatly expands current knowledge surrounding relationships between these indwelling and surface signals, both in the inclusion of the indwelling posterior supraspinatus recordings and the expansion of arm postures examined. These findings indicate that relationships between the surface and indwelling signals are altered by plane of elevation, load and elevation angle, and the surface signal more closely predicts anterior region activity. Examining Changes of In Vitro Supraspinatus Mechanical Properties in a Rat Model: The purposes of this study were 1) to complete in vitro mechanical tissue testing in scenarios emulative of empirical muscular activation and postural conditions in an animal model, and 2) to determine the relative influences of arm posture and external loading levels on tissue responses. Forty-eight shoulders harvested from Sprague-Dawley rats were affixed into custom 3D printed mounting pots and placed into one of eight testing groups combining glenohumeral posture and load magnitude. Orientations represented four different postures observed in vivo, and applied tensile load within the animal model was scaled from human activation of the two supraspinatus regions collected from in vivo research for 1500 cycles. A three-way interaction between elevation angle, load magnitude and cycle number occurred for tangent stiffness within specific cycles, with increasing angles, loads and cycles increasing stiffness by up to 49% in some scenarios; differences in maximum and minimum displacement indicated elevated tissue responses in higher elevation angles. Interactions between elevation angle, load intensity and cycle number altered stretch ratio characteristics, with increased elevation angles, loads and cycles increasing stretch ratios, as well as differentiating articular and bursal side responses. Complex interactions between angle, load and cycle number suggest higher abduction angles, increased load magnitude and subsequent cycles generated increased tendon response characteristics. Novel thesis contributions: Multiple novel findings and contributions originated from this work. This dissertation has combined in vivo and in vitro methodologies to advance understanding of rotator cuff mechanics. This dissertation supports the notion that supraspinatus loading varies throughout the range of motion, and postural and external load variations alter tissue-level supraspinatus responses. Activations of the anterior and posterior regions of the supraspinatus were collected from the largest collection of postures to date and described activation differences between these regions. These EMG activations were used to assist in determining applied force load levels for mechanical testing, representing the first known attempt to generate force-controlled tensile loading using physiologically derived exposure levels for the supraspinatus. This work is also the first to maintain a functional glenohumeral unit to complete mechanical testing using postures representative of those observed in vivo to examine supraspinatus responses. General conclusions: Posture and load magnitude have distinct and noteworthy effects on supraspinatus, both in muscular activation and tendon responses. This research combined in vivo muscular activation with in vitro mechanical tissue testing to generate novel findings for rotator cuff loading; further work should continue to pair in vivo responses with mechanical tendon loading to generate physiologically relevant research scenarios throughout the range of humeral postures. This work has established that the supraspinatus is sensitive to scenario conditions, but continued expansion of our understanding of exposure aspects would help diagnose or anticipate overexposure