No description available.

Abstract Isokinetic normative data can be invaluable in identifying an individual’s strengths and weaknesses, and thus lead to a more effective use of the individual’s time to minimise or overcome his weaknesses while maintaining or improving existing strength. However, visual feedback (VF) may significantly affect the result of isokinetic testing, resulting in erroneous conclusions if not accounted for. Additionally, the previous use of VF to obtain increased strength values has resulted in inconsistent findings. The purpose of this study was to examine the effect of VF on concentric and eccentric knee extensor peak torque. Twenty-two sedentary, college-aged male and female volunteers were assigned to either Group 1 (n = 11) or Group 2 (n = 11) to either perform knee extensor concentric-eccentric (con-ecc) isokinetic testing with VF or without VF (no-VF) using a crossover method. After a one-week rest, the two groups underwent knee extensor con-ecc isokinetic testing using the alternative testing condition. Each test consisted of five maximal knee extensor con-ecc isokinetic testing contractions at 60° per second on the Cybex Norm system. The data indicated significant (p < 0.05) differences in the concentric peak torque of Group 1, Group 2 and Combined Group following VF when compared to no-VF. The eccentric peak torque of Group 1, Group 2 and Combined Group was found not to be significantly different following VF when compared to no-VF. Further, no significant interaction effect as a result of the different groups was found. Visual feedback of torque output can improve maximum voluntary concentric contraction in isokinetic dynamometry, but not maximum voluntary eccentric contraction. It is thus recommended that VF should be consistently provided during isokinetic testing, since it can also be used to help detect and correct errors in performance as well as derive reinforcement from correct performances.

No description available.

Overtraining is a common problem in athletes that prevents many from becoming "elite". A decrement in an athlete's performance is usually an indicator that overtraining syndrome may be developing. Unfortunately, there is no model that can determine overtraining. A decline in performance results in a depression in maximum muscular force. It is not known whether the force depression is a result of central or peripheral factors. In this study, the two training protocols on different legs determined whether force declines are muscular (peripheral) or psychological (central). Specifically, in this study, the subjects trained one leg at maximal intensity for two weeks, and the other trained at a low intensity for two weeks. After training for two weeks, both legs were placed on a low intensity workout to monitor the recovery process. The purpose of this study was to observe muscle strength performance decrements after overtraining one leg in comparison to properly training the other leg by knee extension exercises for two weeks in trained males. Also, after overtraining the one leg for two weeks, the leg was placed on a reduced training program in order to look at recovery if overtraining occurred. Maximal force output was measured isokinetically on the Biodex three times: pre-, post-, and final test. An analysis of this data revealed no significant changes in maximal muscular force output after a high intensity training protocol. Therefore, this investigation demonstrated that overtraining in the quadricep did not result from the two weeks of high intensity resistance training. / Master of Science

<p>Our healthcare system is experiencing a substantial economic burden, and one of the contributing factors is ankle injury - particularly ankle sprains - and the resulting chronic conditions like ankle instability and osteoarthritis. Ankle sprains commonly occur in sports such as basketball, where sudden, lateral changes in direction are common. As a shoe provides the foundational support for an athlete, a simple slipping/tipping analysis was performed to derive a stability criterion that relates impact forces and shoe geometry. The criterion was populated with geometric measurements from seven currently-available basketball shoes and impact forces seen in lateral maneuvers from several published studies to generate multiple cases to observe if the shoes were safe. Of the 35 cases (seven different shoes applied in six different loading conditions) there were six cases where the shoe passed the stability criterion and was considered safe. Given that the impact forces in lateral movements likely will not change, the geometry of the shoes should be considered to reduce the chance of tipping of the shoe (i.e. rolling of the ankle) and risk of injury to the athlete.</p><p>Another contributing factor to the healthcare system's economic burden is limb loss, and the negative effects of ill-fitting and ill-functioning prosthetic devices. Examples of these secondary complications are osteoarthritis and tissue breakdown, which are thought to result from uneven joint loading and asymmetric gait. In light of this, a prosthetic ankle was developed that employs a three degree of freedom system modeled with a ball-in-socket joint. The range of motion of this joint can be custom-bounded by the system of nubs and cavities, along with shims that can be inserted around the joint shaft, to control dorsiflexion, plantarflexion, inversion, eversion, and medial/lateral rotation in the transverse plane. A joint like this, which enables the user to have a more natural gait, will help reduce the onset of conditions like osteoarthritis, ultimately reducing the demand on resources from the healthcare system.</p><p>Another effort to mitigate the burden on the healthcare system is seen through the development of a wearable resistance device that is designed to help prevent injury by strengthening musculoskeletal and neuromuscular systems during sport-specific movements. While traditional gym training is beneficial for an athlete's overall health and fitness, it tends to lack in adequately preparing the athlete for sport-specific movements. Thus, a wearable resistance system is beneficial in that it can provide resistance training during sport to enhance and strengthen an athlete's neuromuscular and musculoskeletal systems. In this study, five recreational runners performed running trials on an instrumented treadmill with and without the wearable resistance system. Force plate and surface electromyography (sEMG) data were collected to observe changes in the muscle activation in both legs. Additionally, sEMG data was examined to detect any effect on left/right symmetry in each subject. </p><p>These studies can all be enhanced with the incorporation of a newly-developed skeletal muscle force model that provides more accurate estimates of individualized muscle forces to better predict surrounding musculoskeletal tissue and joint contact loading. It is founded in dimensional analysis and uses electromyography and the muscle force-length, force-velocity, and force-frequency curves as inputs. The constitutive equation gives way to a unique application of inverse-dynamics that avoids the issue of indeterminacy when reaction moments and ligament loading are minimized in a joint. The ankle joint is used as an example for developing the equations that culminate into a system of linear equations. Seventeen subjects (8 males, 9 females) performed five different exercises geared towards activating the primary muscles crossing the ankle joint. The moments about the ankle joint due to the calculated muscle forces were compared to the sum of the moments due to all other sources and the kinematic terms in the second Newton-Euler equation of rigid body motion. Average percent errors for the \(\vec{B}\) components for each subject ranged from 4.2\% to 15.5\% with a total average percent error across all subjects of 8.2\%. Not only is this muscle force model physiologically relevant, but it can be calibrated and used to predict joint contact loading and loading in the surrounding tissues. Thus, it will be beneficial for use in designing biomechanics equipment for athletes like basketball players, or in designing prosthetic devices that function more like a natural joint. Furthermore, this model can be used in conjunction with the wearable resistance device to validate it's effects on the strengthening of neuromuscular and musculoskeletal systems over time.</p>

BACKGROUND: Nemaline myopathy (NM), the most common non-dystrophic congenital myopathy, is characterized by generalized skeletal muscle weakness, often from birth. To date, no therapy exists that enhances the contractile strength of muscles of NM patients. Mutations in NEB, encoding the giant protein nebulin, are the most common cause of NM. The pathophysiology of muscle weakness in NM patients with NEB mutations (NEB-NM) includes a lower calcium-sensitivity of force generation. We propose that the lower calcium-sensitivity of force generation in NEB-NM offers a therapeutic target. Levosimendan is a calcium sensitizer that is approved for use in humans and has been developed to target cardiac muscle fibers. It exerts its effect through binding to slow skeletal/cardiac troponin C. As slow skeletal/cardiac troponin C is also the dominant troponin C isoform in slow-twitch skeletal muscle fibers, we hypothesized that levosimendan improves slow-twitch muscle fiber strength at submaximal levels of activation in patients with NEB-NM. METHODS: To test whether levosimendan affects force production, permeabilized slow-twitch muscle fibers isolated from biopsies of NEB-NM patients and controls were exposed to levosimendan and the force response was measured. RESULTS: No effect of levosimendan on muscle fiber force in NEB-NM and control skeletal muscle fibers was found, both at a submaximal calcium level using incremental levosimendan concentrations, and at incremental calcium concentrations in the presence of levosimendan. In contrast, levosimendan did significantly increase the calcium-sensitivity of force in human single cardiomyocytes. Protein analysis confirmed that the slow skeletal/cardiac troponin C isoform was present in the skeletal muscle fibers tested. CONCLUSIONS: These findings indicate that levosimendan does not improve the contractility in human skeletal muscle fibers, and do not provide rationale for using levosimendan as a therapeutic to restore muscle weakness in NEB-NM patients. We stress the importance of searching for compounds that improve the calcium-sensitivity of force generation of slow-twitch muscle fibers. Such compounds provide an appealing approach to restore muscle force in patients with NEB-NM, and also in patients with other neuromuscular disorders.

With a prevalence of 17% in men and 4% in women, Femoroacetabular Impingement (FAI) of type cam is characterized by a decreased femoral head-neck offset and/or asphericity of the lateral femoral head, associated with groin pain and reduced hip range of motion. Since the aetiology is still unclear, the mechanisms of development, progression and degeneration of FAI are largely investigated. Musculoskeletal modeling can support the development of a biomechanical framework to advance the research on FAI pathomechanisms, expand the knowledge about hip contact load distribution in FAI population, and relate the muscle and hip contact forces to the alterations observed during functional tasks. Therefore, this thesis is composed of two parts: the development of a methodological framework, and its application to the investigation of FAI pathomechanisms. The variability of the modelling outcomes (i.e.., body kinematics, torques, contact and muscle forces) to different marker sets, pelvic marker misplacements, and hip joint center (HJC) location was investigated within an inverse kinematic framework. The findings from such studies supported the modelling choices for the clinical investigation of FAI pathomechanisms. In particular, the performance of three different marker sets (Plug-in-Gait, University of Ottawa Motion Analysis Model and a 3-marker-cluster marker set) was compared, and absolute and relative reliability indices were calculated with the purpose of finding a simple yet reliable marker set to be used within an inverse kinematic framework in a clinical study. Thereafter, the sensitivity of joint angles, moments and hip contact forces to simulated inaccurate pelvic tilt was analyzed. The resulting variability indices were high with variations up to 1.3 times the body weight in hip contact forces. The kinematic variations propagated non-linearly to all planes and joints, showing the importance of adjusting possible pelvic misalignments. A methodology was presented to correct the pelvic alignment when the relative position of surface pelvic markers with respect to bony landmarks is known from medical images. The HJC location is a crucial modelling parameter in the analysis of hip kinematics and forces. A certain degree of customization could be introduced in the model by using HJC measured from medical images. Therefore, the performance of a generic musculoskeletal model with customized or non-customized HJC was compared during walking. Hip contact forces were highly sensitive to HJC location, especially because of the dependency of muscle moment arms to HJC changes. However, the variation of HJC without consistent muscle anatomy customization introduced artifacts that could potentially produce inaccurate muscle and joint contact forces estimation. When HJC cannot be measured from medical images, regression equations can be used instead. Therefore, the validity of two popular HJC regression equations (Harrington and Davis) was tested on FAI participants using non-parametric statistical and Bland-Altman tests. The results indicated that the equations were valid for FAI population. In addition, skin thickness measurements were provided for pelvic bony landmarks, and their correlation with body mass index was proposed for systematic error reduction. New adult-specific regression equations were developed from medical images. The described methodological framework was then applied to investigate the functional alterations observed in FAI population. The differences in muscle and hip contact forces were compared between FAI and healthy control groups during level walking. The FAI group showed reduced muscle and hip contact forces, which were linked to the lower normalized walking speed and shorter step length. These results can be interpreted as a protective mechanism developed by FAI patients to prevent high compression at the site of impingement, given that the compressing hip contact force was directed towards the anterior-superior quadrant of the acetabulum, consistent with the localization of the cam-type deformity and the cartilage and labrum damages. Based on these findings, a possible FAI pathomechanism was proposed, which could be used to support the development of preventive treatment and intervention for symptomatic FAI patients.

Unbalanced muscle forces in the shoulder joint may lead to functional impairment in the setting of rotator cuff tear and progressive arthritis in cuff tear arthropathy. A model, which predicts muscle forces for common shoulder movements, could be used to help in treatment decision-making and in improving the design of total shoulder prosthesis. Unfortunately, the shoulder has many muscles that overlap in function leading to an indeterminate system. A finite element model employing an optimization algorithm could be used to reduce the number of degrees of freedom and predict loading of the glenohumeral joint. The goal of this study was to develop an anatomically and physiologically correct computational model of the glenohumeral joint. This model was applied to: 1) estimate the force in each muscle during the standard glenohumeral motions (flexion/extension, abduction/adduction and internal/ external rotation), and 2) determine stress concentrations within the scapula during these motions. These goals were realized through the following steps: First, a three dimensional bone reconstruction was performed using computed tomography (CT) scan data. This allowed for a precise anatomical representation of the bony components. Then muscle lever arms were estimated based on the reconstructed bones using computer-aided design software. The origins, insertions, and muscle paths were obtained from the literature. This model was then applied to estimate the forces within each of the muscles that are necessary to stabilize the joint at a fixed position. Last, finite element analysis of the scapula was performed to study the stress concentrations. These were identified and related to the morphology of the bone. A force estimation algorithm was then developed to determine the necessary muscle force distribution. This algorithm was based on an applied external moment at the joint, and the appropriate selection of muscles that could withstand it, ensuring stability, while keeping the reaction force at a minimum. This method offered an acceptable solution to the indeterminate problem, a unique solution was found for each shoulder motion. The model was then applied to determine the stress concentration within various regions of the scapula for each of the shoulder motions. The rotator cuff was found to act as the main stabilizer under rotation, and had a significant stabilizing role under flexion and abduction. The finite element model of the shoulder that was developed can be used to gain a better understanding of the load transfer mechanisms within the glenohumeral joint and the impact of muscle forces on scapular morphology. This information can then be used to assist with treatment decision-making for rotator cuff tears and with the design of new implants for total shoulder arthroplasty.

Esta tese está dividida em três estudos. No estudo I desta tese, os objetivos foram descrever a cinemática tridimensional do ombro e determinar a contribuição da articulação escápulotorácica no movimento total de elevação. No estudo II, os objetivos foram descrever a atividade eletromiográfica (EMG) e o percentual de cocontração entre os músculos deltóide médio e redondo maior. No estudo III, o objetivo foi determinar o valor máximo da força de contato gleno-umeral e da força muscular. Quarenta sujeitos participaram dos estudos divididos em três grupos: pacientes com prótese total do ombro (PTO), com prótese reversa (PRO) e um grupo controle. Todos realizaram dois exercícios de reabilitação (flexão e elevação no plano escapular) usando diferentes cargas (sem carga externa, halter de 1kg e resistência elástica). A cinemática do ombro foi registrada por meio de um dispositivo eletromagnético de rastreamento, a atividade EMG foi registrada por meio de um eletromiógrafo de 16 canais e o modelo matemático utilizado foi o Delft Shoulder and Elbow Model. As análises estatísticas foram feitas por meio de ANOVAs de dois e três fatores para medidas repetidas. Foi utilizado o teste post hoc de Bonferroni e o nível de significância adotado foi de α < 0,05. Os resultados do estudo I mostram que a escápula contribui mais para o movimento total do ombro em pacientes com prótese em relação aos indivíduos saudáveis e em exercícios realizados com 1 kg e resistência elástica comparados com os exercícios sem carga externa. O ângulo de elevação glenoumeral durante a flexão foi significativamente maior no grupo PTO em comparação ao grupo PRO. O estudo II identificou maior atividade EMG do deltóide médio e posterior no grupo PTO em comparação ao grupo controle e um aumento da atividade EMG do peitoral (parte esternal) no grupo PRO em comparação ao grupo PTO e ao grupo controle. Para os outros músculos (deltóide anterior, redondo maior, peitoral maior - parte clavicular e serrátil anterior) não foram encontradas diferenças significativas entre os grupos. Para todos os músculos, exceto o serrátil anterior, a atividade EMG foi menor nos exercícios sem carga externa quando comparados aos exercícios com 1 kg e resistência elástica. Nenhum efeito principal dos fatores grupo e carga foi encontrado no percentual de cocontração. No estudo III, o grupo controle apresentou maior força de contato gleno-umeral máxima quando comparado ao grupo PTO durante a flexão, mas não foram encontradas diferenças entre os grupos de pacientes nos dois movimentos. A resistência elástica apresentou maiores valores de força de contato gleno-umeral em todos os grupos. O valor máximo da força de todos os músculos analisados variou de 0,32 N a 772 N e o manguito rotador e o deltóide foram os músculos que apresentaram os maiores valores de força em todos os grupos. A presente tese sugere que para uma mesma amplitude de movimento, os pacientes com prótese de ombro apresentarão um movimento escapular maior compensando a perda do movimento gleno-umeral. A cinemática escapular e a atividade EMG destes pacientes foram influenciadas pela implementação de cargas externas, mas não pelo tipo de carga, diferentemente das forças de contato e das forças musculares, nas quais a resistência elástica apresentou maior influência. Além disso, o percentual de cocontração não foi influenciado pelo tipo de prótese e os grupos de pacientes apresentaram menores forças de contato gleno-umeral do que o grupo controle. / This thesis is divided into three studies. In study I, the objectives were to describe shoulder three-dimensional kinematics and to determine the contribution of scapulothoracic motion in total shoulder elevation. In study II, the objectives were to describe the electromyographic activity (EMG) and the percentage of cocontraction between middle deltoid and teres major. In study III, the objective was to determine the maximum glenohumeral contact force and shoulder muscle forces. Forty subjects participated in the studies divided into three groups: patients with total shoulder prosthesis (TSP), patients with reverse shoulder prosthesis (RSP) and a control group. All patients realized two rehabilitation exercises (anteflexion and elevation in the scapular plane) using different loads (without external load, 1 kg dumbbell and elastic resistance). Shoulder kinematics was recorded by means of an electromagnetic tracking device, the EMG activity was recorded through a 16-channel EMG system and the Delft Shoulder and Elbow Model was used. Statistical analyses were performed by means of repeated measures ANOVAs. The Bonferroni post hoc test was used and the adopted significance level was α <0.05. Results of study I showed that the scapula contributes more to the total movement of the shoulder in patients with prosthesis compared to healthy subjects and in exercises performed with 1 kg and elastic resistance compared to exercises without external load. The glenohumeral elevation angle during anteflexion was significantly higher in the TSP group compared to the RSP. The study II identified higher EMG activity of the middle and posterior deltoid in the TSP group compared to the control group and an increase of EMG activity of pectoralis major (sternal part) in the RSP group compared to the TSP and the control group. For the other muscles (anterior deltoid, teres major, pectoralis major - clavicular part and serratus anterior) significant differences were not found among groups. For all muscles, except the serratus anterior, EMG activity was lower during exercises without external load compared to exercises with 1 kg and elastic resistance. No main effect of group and load was found in the percentage of cocontraction. In study III, the control group showed higher maximum glenohumeral contact force when compared to TSP group during anteflexion, but no differences were found between groups of patients during both movements. Elastic resistance exercises showed higher glenohumeral contact force in all groups. The maximum force of all analyzed muscles ranged from 0,32 N to 772 N and the rotator cuff and deltoid muscles presented the highest values in all groups. This thesis suggests that for a same range of motion, patients with shoulder prosthesis present greater scapular motion compensating the loss of glenohumeral motion. Scapular kinematics and EMG activity of these patients were affected by the implementation of external loads, but not by the type of load, unlike the contact forces and muscle forces, in which the elastic resistance had greater influence. Moreover, the percentage of cocontraction was not influenced by the type of prosthesis and patient groups had lower glenohumeral contact forces compared to the control group.

Esta tese está dividida em três estudos. No estudo I desta tese, os objetivos foram descrever a cinemática tridimensional do ombro e determinar a contribuição da articulação escápulotorácica no movimento total de elevação. No estudo II, os objetivos foram descrever a atividade eletromiográfica (EMG) e o percentual de cocontração entre os músculos deltóide médio e redondo maior. No estudo III, o objetivo foi determinar o valor máximo da força de contato gleno-umeral e da força muscular. Quarenta sujeitos participaram dos estudos divididos em três grupos: pacientes com prótese total do ombro (PTO), com prótese reversa (PRO) e um grupo controle. Todos realizaram dois exercícios de reabilitação (flexão e elevação no plano escapular) usando diferentes cargas (sem carga externa, halter de 1kg e resistência elástica). A cinemática do ombro foi registrada por meio de um dispositivo eletromagnético de rastreamento, a atividade EMG foi registrada por meio de um eletromiógrafo de 16 canais e o modelo matemático utilizado foi o Delft Shoulder and Elbow Model. As análises estatísticas foram feitas por meio de ANOVAs de dois e três fatores para medidas repetidas. Foi utilizado o teste post hoc de Bonferroni e o nível de significância adotado foi de α < 0,05. Os resultados do estudo I mostram que a escápula contribui mais para o movimento total do ombro em pacientes com prótese em relação aos indivíduos saudáveis e em exercícios realizados com 1 kg e resistência elástica comparados com os exercícios sem carga externa. O ângulo de elevação glenoumeral durante a flexão foi significativamente maior no grupo PTO em comparação ao grupo PRO. O estudo II identificou maior atividade EMG do deltóide médio e posterior no grupo PTO em comparação ao grupo controle e um aumento da atividade EMG do peitoral (parte esternal) no grupo PRO em comparação ao grupo PTO e ao grupo controle. Para os outros músculos (deltóide anterior, redondo maior, peitoral maior - parte clavicular e serrátil anterior) não foram encontradas diferenças significativas entre os grupos. Para todos os músculos, exceto o serrátil anterior, a atividade EMG foi menor nos exercícios sem carga externa quando comparados aos exercícios com 1 kg e resistência elástica. Nenhum efeito principal dos fatores grupo e carga foi encontrado no percentual de cocontração. No estudo III, o grupo controle apresentou maior força de contato gleno-umeral máxima quando comparado ao grupo PTO durante a flexão, mas não foram encontradas diferenças entre os grupos de pacientes nos dois movimentos. A resistência elástica apresentou maiores valores de força de contato gleno-umeral em todos os grupos. O valor máximo da força de todos os músculos analisados variou de 0,32 N a 772 N e o manguito rotador e o deltóide foram os músculos que apresentaram os maiores valores de força em todos os grupos. A presente tese sugere que para uma mesma amplitude de movimento, os pacientes com prótese de ombro apresentarão um movimento escapular maior compensando a perda do movimento gleno-umeral. A cinemática escapular e a atividade EMG destes pacientes foram influenciadas pela implementação de cargas externas, mas não pelo tipo de carga, diferentemente das forças de contato e das forças musculares, nas quais a resistência elástica apresentou maior influência. Além disso, o percentual de cocontração não foi influenciado pelo tipo de prótese e os grupos de pacientes apresentaram menores forças de contato gleno-umeral do que o grupo controle. / This thesis is divided into three studies. In study I, the objectives were to describe shoulder three-dimensional kinematics and to determine the contribution of scapulothoracic motion in total shoulder elevation. In study II, the objectives were to describe the electromyographic activity (EMG) and the percentage of cocontraction between middle deltoid and teres major. In study III, the objective was to determine the maximum glenohumeral contact force and shoulder muscle forces. Forty subjects participated in the studies divided into three groups: patients with total shoulder prosthesis (TSP), patients with reverse shoulder prosthesis (RSP) and a control group. All patients realized two rehabilitation exercises (anteflexion and elevation in the scapular plane) using different loads (without external load, 1 kg dumbbell and elastic resistance). Shoulder kinematics was recorded by means of an electromagnetic tracking device, the EMG activity was recorded through a 16-channel EMG system and the Delft Shoulder and Elbow Model was used. Statistical analyses were performed by means of repeated measures ANOVAs. The Bonferroni post hoc test was used and the adopted significance level was α <0.05. Results of study I showed that the scapula contributes more to the total movement of the shoulder in patients with prosthesis compared to healthy subjects and in exercises performed with 1 kg and elastic resistance compared to exercises without external load. The glenohumeral elevation angle during anteflexion was significantly higher in the TSP group compared to the RSP. The study II identified higher EMG activity of the middle and posterior deltoid in the TSP group compared to the control group and an increase of EMG activity of pectoralis major (sternal part) in the RSP group compared to the TSP and the control group. For the other muscles (anterior deltoid, teres major, pectoralis major - clavicular part and serratus anterior) significant differences were not found among groups. For all muscles, except the serratus anterior, EMG activity was lower during exercises without external load compared to exercises with 1 kg and elastic resistance. No main effect of group and load was found in the percentage of cocontraction. In study III, the control group showed higher maximum glenohumeral contact force when compared to TSP group during anteflexion, but no differences were found between groups of patients during both movements. Elastic resistance exercises showed higher glenohumeral contact force in all groups. The maximum force of all analyzed muscles ranged from 0,32 N to 772 N and the rotator cuff and deltoid muscles presented the highest values in all groups. This thesis suggests that for a same range of motion, patients with shoulder prosthesis present greater scapular motion compensating the loss of glenohumeral motion. Scapular kinematics and EMG activity of these patients were affected by the implementation of external loads, but not by the type of load, unlike the contact forces and muscle forces, in which the elastic resistance had greater influence. Moreover, the percentage of cocontraction was not influenced by the type of prosthesis and patient groups had lower glenohumeral contact forces compared to the control group.