The Stabilizing Function of Superficial Shoulder Muscles Changes Between Single-Plane Elevation and Reaching Tasks

Objective: The goal of the current study was to determine whether and how much the stabilizing role of the shoulder muscles changes as a function of humeral elevation and the plane of elevation. Methods: A musculoskeletal model, comprising a personalized scapulohumeral rhythm, was used to calculate the ratio of shear over compressive force (stability ratio) of three rotator cuff muscles (supraspinatus, infraspinatus, subscapularis) and three superficial shoulder muscles (middle deltoid, clavicular part of pectoralis major, latissimus dorsi) during abduction, flexion and reaching movements in ten healthy adults. Results: The range of the stability ratios was [±0.5] for the rotator cuff muscles compared to [+5, −2] for the superficial shoulder muscles. In the superior-inferior direction, the stability ratios of all muscles changed with humeral elevation and for infraspinatus, subscapularis, latissimus dorsi and deltoid also with the plane of elevation. In the anterior-posterior direction, the stability ratios of all muscles changed with humeral elevation, except for the deltoid, and with the plane of elevation, except for the supraspinatus, with interaction effects in all muscles. Conclusion: The rotator cuff muscles provide greater compression than shear forces during all tasks. The stabilizing function of the superficial shoulder muscles examined in this study varies during tasks. Significance: The findings can be used to predict in which movements the shoulder joint becomes more unstable and can be applied to understand how shear and compressive forces change in populations with abnormal shoulder motion

Evaluation of Concavity Compression Mechanism as a Possible Predictor of Shoulder Muscle Fatigue

This study examined the lived experiences of American Muslim principals who serve in public schools post-9/11 to determine whether global events, political discourse, and the media coverage of Islam and Muslims have affected their leadership and spirituality. The aim of the study was to allow researchers and educators to gain an understanding of the adversities that American Muslims principals have experienced post-9/11 and to determine how to address these adversities, particularly through decisions about educational policy and district leadership. A total of 14 American Muslim school leaders who work in public schools post-9/11 across the United States participated in the study, and a phenomenological methodology was used to direct the data collection and coding. Edelman\u27s political spectacle theory served as the theoretical framework for the research. The findings yielded six themes of political climate, role of the media, inferior and foreign: being seen as the other, unconscious fear, spirituality, and education and communication over spectacle. Further, collective guilt and social responsibility emerged as two additional findings. The research suggests that political spectacle and its effects have a large impact on the lives of American Muslim principals, particularly in regard to their leadership and spirituality

Superficial shoulder muscle synergy analysis in Facioscapulohumeral Dystrophy during humeral elevation tasks

Facioscapulohumeral Dystrophy (FSHD) is a progressive muscle-wasting disease which leads to a decline in upper extremity functionality. Although the scapulohumeral joint's stability and functionality are affected, evidence on the synergetic control of the shoulder muscles in FSHD individuals is still lacking. The aim of this study is to understand the neuromuscular changes in shoulder muscle control in people with FSHD. Upper arm kinematics and electromyograms (EMG) of eight upper extremity muscles were recorded during shoulder abduction-adduction and flexion-extension tasks in eleven participants with FSHD and eleven healthy participants. Normalized muscle activities were extracted from EMG signals. Non-negative matrix factorization was used to compute muscle synergies. Maximum muscle activities were compared using non-parametric analysis of variance. Similarities between synergies were also calculated using correlation. The Biceps Brachii was significantly more active in the FSHD group (25±2%) while Trapezius Ascendens and Serratus Anterior were less active (32±7% and 39±4% respectively). Muscle synergy weights were altered in FSHD individuals and showed greater diversity while controls mostly used one synergy for both tasks. The decreased activity by selected scapula rotator muscles and muscle synergy weight alterations show that neuromuscular control of the scapulohumeral joint is less consistent in people with FSHD compared to healthy participants. Assessments of muscle coordination strategies can be used to evaluate motor output variability and assist in management of the disease

Development and Biomechanical Analysis toward a Mechanically Passive Wearable Shoulder Exoskeleton

Shoulder disability is a prevalent health issue associated with various orthopedic and neurological conditions, like rotator cuff tear and peripheral nerve injury. Many individuals with shoulder disability experience mild to moderate impairment and struggle with elevating the shoulder or holding the arm against gravity. To address this clinical need, I have focused my research on developing wearable passive exoskeletons that provide continuous at-home movement assistance. Through a combination of experiments and computational tools, I aim to optimize the design of these exoskeletons. In pursuit of this goal, I have designed, fabricated, and preliminarily evaluated a wearable, passive, cam-driven shoulder exoskeleton prototype. Notably, the exoskeleton features a modular spring-cam-wheel module, allowing customizable assistive force to compensate for different proportions of the shoulder elevation moment due to gravity. The results of my research demonstrated that this exoskeleton, providing modest one-fourth gravity moment compensation at the shoulder, can effectively reduce muscle activity, including deltoid and rotator cuff muscles. One crucial aspect of passive shoulder exoskeleton design is determining the optimal anti-gravity assistance level. I have addressed this challenge using computational tools and found that an assistance level within the range of 20-30% of the maximum gravity torque at the shoulder joint yields superior performance for specific shoulder functional tasks. When facing a new task dynamic, such as wearing a passive shoulder exoskeleton, the human neuro-musculoskeletal system adapts and modulates limb impedance at the end-limb (i.e., hand) to enhance task stability. I have presented development and validation of a realistic neuromusculoskeletal model of the upper limb that can predict stiffness modulation and motor adaptation in response to newly introduced environments and force fields. Future studies will explore the model\u27s applicability in predicting stiffness modulation for 3D movements in novel environments, such as passive assistive devices\u27 force fields

Shoulder muscle activation strategies differ when lifting or lowering a load

Purpose Lowering a load could be associated with abnormal shoulder and scapular motion. We tested the hypothesis that lowering a load involves different shoulder muscle coordination strategies compared to lifting a load. Methods EMG activity of 13 muscles was recorded in 30 healthy volunteers who lifted and lowered a 6, 12 or 18 kg box between three shelves. Kinematics, EMG levels and muscle synergies, extracted using non-negative matrix factorization, were analyzed. Results We found greater muscle activity level during lowering in four muscles (+ 1–2% MVC in anterior deltoid, biceps brachii, serratus anterior and pectoralis major). The movements were performed faster during lifting (18.2 vs. 15.9 cm/s) but with similar hand paths and segment kinematics. The number of synergies was the same in both tasks. Two synergies were identified in ~ 75% of subjects, and one synergy in the others. Synergy #1 mainly activated prime movers’ muscles, while synergy #2 co-activated several antagonist muscles. Synergies’ structure was similar between lifting and lowering (Pearson’s r ≈ 0.9 for synergy #1 and 0.7–08 for synergy #2). Synergy #2 was more activated during lowering and explained the greater activity observed in anterior deltoid, serratus anterior and pectoralis. Conclusion Lifting and lowering a load were associated with similar synergy structure. In 3/4 of subjects, lowering movements involved greater activation of a “multiple antagonists” synergy. The other subjects co-contracted all shoulder muscles as a unit in both conditions. These inter-individual differences should be investigated in the occurrence of shoulder musculoskeletal disorders

Comparative Forelimb Muscle Function in Turtles: Tests of Environmental Variation and Neuromotor Conservation

Novel locomotor functions in animals may evolve through changes in morphology, muscle activity, or a combination of both. The idea that new functions or behaviors can arise solely through changes in structure, without concurrent changes in the patterns of muscle activity that control movement of those structures, has been formalized as the `neuromotor conservation hypothesis\u27. In vertebrate locomotor systems, evidence for neuromotor conservation is found across transitions in terrestrial species and into fliers, but transitions in aquatic species have received little comparable study to determine if changes in morphology and muscle function were coordinated through the evolution of new locomotor behaviors. Understanding how animals move has long been an important component of integrative comparative biology and biomechanics. This topic can be divided into two components, the motion of the limbs, and the muscles that move them. Variation in these two parameters of movement is typically examined at three levels, intraspecfic studies of different behaviors, and interspecific studies on either the same or different behaviors. My dissertation is a compilation of four studies that examined forelimb kinematics and motor control across locomotor modes in freshwater and marine turtles to determine how muscle function is modulated in the evolution of new locomotor styles. First, I described patterns of forelimb motion and associated patterns of muscle activation during swimming and walking in a generalized freshwater turtle species (Trachemys scripta) to show how muscle function is modulated to accommodate the different performance demands imposed by water and land. Second, I examined whether differences in muscle function are correlated with changes in limb morphology and locomotor style by comparing forelimb kinematics and motor patterns of swimming from rowing Trachemys scripta to those of flapping sea turtles (Caretta caretta). Next, I quantified forelimb kinematics of swimming in the freshwater turtle species Carettochelys insculpta, describing how it uses synchronous forelimb movements to swim and whether these motions are actually similar to the flapping kinematics of sea turtles (Caretta caretta) or if they more closely resemble the kinematics of freshwater species with which they are more phylogenetically similar. I also compared the kinematics of rowing in Trachemys scripta and the highly aquatic Florida softshell turtle (Apalone ferox). Finally, I compared patterns of forelimb muscle activation for four species of turtles to determine whether the chelonian lineage shows evidence of neuromotor conservation across the evolution of different locomotor modes. Data from these studies help improve our understanding of how new forms of quadrupedal locomotion have evolved

The efficacy of using human myoelectric signals to control the limbs of robots in space

This project was designed to investigate the usefulness of the myoelectric signal as a control in robotics applications. More specifically, the neural patterns associated with human arm and hand actions were studied to determine the efficacy of using these myoelectric signals to control the manipulator arm of a robot. The advantage of this approach to robotic control was the use of well-defined and well-practiced neural patterns already available to the system, as opposed to requiring the human operator to learn new tasks and establish new neural patterns in learning to control a joystick or mechanical coupling device

Pilates and String Musicians: An Exploration of the Issues Addressed by the Pilates Method, an Illustrated Guide to Adapted Exercises, and a Pilates Course for University String Players

abstract: String players have been identified as the most affected group of instrumentalists suffering from musculoskeletal disorders, and most of the problems are related to posture. The high prevalence of injuries among string players suggests that there is room in the music curriculum for a program tailored to this population and that can provide both immediate and long-term solutions. Pilates is a mind-body conditioning method of exercises and a philosophy that shares many similarities with string playing technique and performance, which suggests that its practice can be beneficial to improve not only the posture of string players but also various other areas. Studies about Pilates as a treatment show the varied areas in which Pilates can help, which are all of interest to instrumentalists. However, the application of Pilates into the music curriculum as a way to help string players improve awareness and reduce injuries has not yet been fully explored. This document addresses the similarities between Pilates and string playing, identifies postural tendencies of string players, and demonstrates how specific Pilates exercises can help counteract asymmetries, restore balance, and reduce the number of musculoskeletal injuries of string players. All anatomical drawings included in this document were adapted from other sources, as cited, or originally drawn by the author.Dissertation/ThesisDoctoral Dissertation Music 201

The Effects of Injury on the Neuromotor Control of the Shoulder

Abstract: The shoulder is one of the most mobile and unstable joints in the body. When the function of the shoulder muscles is altered, and it is without the appropriate neuromotor control, the shoulder can become dysfunctional. It is unknown how previously injured individuals vary in movement patterns or whether their brains change compared to their healthy counterparts. The purpose of this study was to compare neuromotor control of the shoulder between individuals with and without a previous shoulder injury. To achieve this, we used an upper extremity task with motion capture to analyze kinematic performance of the shoulder complex and electroencephalography (EEG) to evaluate neural connectivity of the brain. We hypothesized that individuals with previous injury to the shoulder would have different kinematic patterns as well as a less direct or evasive way of achieving their goal-oriented trajectory. We also hypothesized that participants with previous shoulder injury to have more diffuse patterns of brain connectivity during performance of the task, as compared to healthy participants. Our kinematic results made it evident that healthy and post-injured individuals have different anterior/posterior trunk displacement and hand pathways toward their targets. Our neurological results showed significant changes in brain connectivity in post-injured individuals across conditions. RPE scoring increased and decreased in response to an increase and decrease in weight resistance, but scores were higher in post-injured individuals. Further research is needed to understand how individuals modify movement kinematics in different joints and determine how consistent these changes are across tasks and patterns of brain activation