Handrim Reaction Force and Moment Assessment Using a Minimal IMU Configuration and Non-Linear Modeling Approach during Manual Wheelchair Propulsion.

Manual wheelchair propulsion represents a repetitive and constraining task, which leads mainly to the development of joint injury in spinal cord-injured people. One of the main reasons is the load sustained by the shoulder joint during the propulsion cycle. Moreover, the load at the shoulder joint is highly correlated with the force and moment acting at the handrim level. The main objective of this study is related to the estimation of handrim reactions forces and moments during wheelchair propulsion using only a single inertial measurement unit per hand. Two approaches are proposed here: Firstly, a method of identification of a non-linear transfer function based on the Hammerstein-Wiener (HW) modeling approach was used. The latter represents a typical multi-input single output in a system engineering modeling approach. Secondly, a specific variant of recurrent neural network called BiLSTM is proposed to predict the time-series data of force and moments at the handrim level. Eleven subjects participated in this study in a linear propulsion protocol, while the forces and moments were measured by a dynamic platform. The two input signals were the linear acceleration as well the angular velocity of the wrist joint. The horizontal, vertical and sagittal moments were estimated by the two approaches. The mean average error (MAE) shows a value of 6.10 N and 4.30 N for the horizontal force for BiLSTM and HW, respectively. The results for the vertical direction show a MAE of 5.91 N and 7.59 N for BiLSTM and HW, respectively. Finally, the MAE for the sagittal moment varies from 0.96 Nm (BiLSTM) to 1.09 Nm for the HW model. The approaches seem similar with respect to the MAE and can be considered accurate knowing that the order of magnitude of the uncertainties of the dynamic platform was reported to be 2.2 N for the horizontal and vertical forces and 2.24 Nm for the sagittal moments. However, it should be noted that HW necessitates the knowledge of the average force and patterns of each subject, whereas the BiLSTM method do not involve the average patterns, which shows its superiority for time-series data prediction. The results provided in this study show the possibility of measuring dynamic forces acting at the handrim level during wheelchair manual propulsion in ecological environments.

Comparative analysis of biomechanical characteristics between the new Tai Chi elastic band exercise for opening and closing movement and elastic band resistance training for the reverse fly movement.

Background: The objective of this study was to compare and analyze the representative opening and closing movement of Tai Chi elastic band exercise with the reverse fly movement of elastic band resistance training. The aim was to explore the biomechanical differences between the two exercises and provide theoretical support for the application of Tai Chi elastic band exercise in health intervention. Methods: A total of 26 male participants were recruited and randomly divided into two groups in a 1:1 ratio. There were 13 participants in each Tai Chi elastic band exercise group and elastic band resistance training group. Both groups of participants used an elastic band to perform movement in the experiment. Experimental data were collected using the Vicon infrared motion capture system and Delsys surface EMG system. The AnyBody software was utilized to simulate the creation of a musculoskeletal model for both exercises. Result: The study found that the Tai Chi elastic band exercise group exhibited smaller horizontal abduction angle and flexion angle of the shoulder joint, as well as normalized RMS of the anterior deltoid and triceps brachii, compared to the elastic band resistance training group (P < 0.01); the Tai Chi elastic band exercise group exhibited greater elbow flexion angle, elbow flexion torque, and muscle strength of the infraspinatus, coracobrachialis, biceps brachii, brachialis and brachioradialis, compared to the elastic band resistance training group (P < 0.01); the Tai Chi elastic band exercise group exhibited smaller horizontal abduction angular velocity of the shoulder joint and a lower normalized RMS of the posterior deltoid, compared to the elastic band resistance training group (P < 0.05). Conclusion: (1) The opening and closing movement of Tai Chi elastic band exercise is characterized by a large elbow flexion angle, a small shoulder joint horizontal angle and flexion angle, and a slow and uniform speed of movement. The reverse fly movement of elastic band resistance training is characterized by a large horizontal abduction angle of the shoulder joint, a large flexion angle of the shoulder joint, a small flexion angle of the elbow joint, and a fast and uneven speed. (2) The opening and closing movement exerts a greater torque on the elbow flexion, while the reverse fly movement exerts a greater torque on the shoulder joint horizontal abduction and external rotation. (3) The opening and closing movement provide greater stimulation to the infraspinatus, coracobrachialis, and elbow flexor, while the reverse fly movement provides greater stimulation to the posterior deltoid, anterior deltoid, subscapularis, and elbow extensor. In summary, the variation in joint angle, joint angular velocity, and hand position could be the factor contributing to the differences in joint torque and muscle activity between the opening and closing movement of Tai Chi elastic band exercise and the reverse fly movement of elastic band resistance training.

New learning technique based on real-time kinematic feedback from an inertial sensor for manual therapy in shoulder joint: a randomised trial.

BACKGROUND: Reducing teacher subjectivity and checking skill corrections have an impact on the manual therapy learning, one of the most crucial components of physical therapy clinical practise. The aim of this study was to analyse the effectiveness of a kinematic real-time feedback strategy (KRTF) with an inertial sensor as a new methodology for the learning of glenohumeral joint mobilisation, comparing it with the traditional teaching method. METHODS: This study was a randomised trial. 59 undergraduate students without experience in manual therapy were randomised into two different groups (G1: Traditional methods group; G2: KRTF group). G1: students would practice the technique while an expert in manual therapy would supervise them. G2: could perform the mobilisation and observe the kinematic characteristics of the technique on a laptop. For the two movements that compose the mobilisation (angulation and translation), the result variables extracted were: maximum displacement, minimum displacement, area under the curve and the difference between the area under the curve of angulation and translation. In addition, the consistency of the measurement and reliability were calculated, too. RESULTS: Some significant differences were observed within groups, between groups and in the group x time interaction, the difference between the angulation and translation area. The synchronization of the movements in in the post comparison was better in G2 because the differences in the areas of both movements were significantly smaller (Mean Difference G1 vs. G2 = 1111.4°s (p > 0.05)). CONCLUSIONS: After comparing the kinematic variables recorded between the two intervention groups analysed in the present study, we observed that the kinematic registers were significantly different between the two groups, with a higher evolution in the KRTF group compared to the traditional learning method. The effectiveness of KRTF was proved over the traditional teaching methods in facilitating the learning process of the glenohumeral joint mobilisation. GOV ID: NCT02504710, 22/07/2015.

Satisfaction of patients with frozen shoulder following silent manipulation: a prospective observation study.

Silent manipulation is a procedure for frozen shoulders that involves manipulating the shoulder while the patient is awake by performing C5, C6, and C7 cervical nerve root block under ultrasound guidance. This retrospective study, conducted at Yokohama City University Hospital, aimed to evaluate the clinical outcomes of silent manipulation and assess whether the experience level of the practitioner influenced treatment efficacy. Between October 2020 and January 2022, 53 patients who met the inclusion criteria underwent silent manipulation for frozen shoulder. The procedure was performed by either an experienced or a less experienced practitioner, and the patients were followed-up for up to 1 year post-treatment. Silent manipulation resulted in significant improvements in shoulder range of motion, as measured by forward flexion, abduction, external rotation, and hand-behind-back, as well as in patient-reported outcomes, including disabilities of the arm, shoulder, and hand and Shoulder 36 scores. These improvements were observed 1 week, 3 months, and 1 year after silent manipulation, indicating the short-term efficacy of the procedure. Furthermore, this study revealed that the practitioners' level of experience played a significant role in the outcomes. The experienced doctor achieved better 1st external rotation and belt tying outcomes, as well as Shoulder 36 pain, muscle strength, and activities of daily living domain scores. This suggests that technical expertise in silent manipulation is crucial to achieve optimal outcomes. Silent manipulation offers an effective therapeutic approach for frozen shoulder, leading to significant improvements in range of motion and patient satisfaction. Practitioner expertise is a vital factor in treatment success, emphasizing the importance of skilled professionals in the performance of this procedure.

Functional Anatomy and Biomechanics of Shoulder Instability.

The glenohumeral joint is the least congruent and least constrained joint with a complex relationship of static and dynamic stabilizers to balance its native mobility with functional stability. In the young athlete, anterior shoulder instability is multifactorial and can be a challenge to treat, requiring a patient-specific treatment approach. Surgical decision-making must consider patient-specific factors such as age, sport activity and level, underlying ligamentous laxity, and goals for return to activity, in addition to careful scrutiny of the underlying pathology to include humeral and glenoid bone loss and surrounding scapular bone morphology.

Isokinetic Strength and Balance Analyses for Predicting Return to Sports After the Latarjet Procedure: A Prospective Cross-sectional Study.

BACKGROUND: Isokinetic torque in shoulder internal rotation (IR) and external rotation (ER) can be considered as potential indicators for dynamic stability of the glenohumeral joint. PURPOSE: To assess the efficacy of 4-month isokinetic testing in predicting the 6-month return-to-sports (RTS) status after Latarjet surgery, explore its correlations with testing parameters, and identify optimal thresholds to ensure a safe RTS. STUDY DESIGN: Cohort study; Level of evidence, 2. METHODS: The study assessed athletes who underwent the Latarjet stabilization procedure between January 2022 and June 2023. The primary outcome was RTS at 6 months after surgery. The primary examined predictors were isokinetic testing metrics at 4 months postoperatively. Secondary outcomes comprised the modified Closed Kinetic Chain Upper Extremity Stability Test (mCKCUEST) and several patient-reported outcome measures, including the Walch-Duplay score, the Western Ontario Shoulder Instability Index (WOSI), and the Shoulder Instability-Return to Sports after Injury scale. To assess the predictors, patients were divided into those who returned to any level of sports compared with those who did not return to sports. The correlation between isokinetic testing results and other outcome scores was also analyzed. RESULTS: A total of 71 patients (mean age, 27.43 ± 9.09 years) were included in the study. Of these, 23.61% did not return to sports, 38.89% returned at a lower level, and 37.50% returned to the same level. Significant rotational strength disparities were noted. Patients who did not return to sports at 6 months demonstrated inferior strength in concentric ER at 60 deg/s, concentric ER at 240 deg/s, concentric IR at 240 deg/s, and eccentric IR at 30 deg/s (P < .05). Similar trends appeared for all studied patient-reported outcome measures and the mCKCUEST (P < .05). Receiver operating characteristic analysis emphasized the significance of isokinetic testing in concentric ER at 240 deg/s (area under the curve = 0.759; P = .001; cutoff = 0.32 N·m/kg; sensitivity = 100.0%; specificity = 49.1%) and eccentric ER at 30 deg/s (area under the curve = 0.760; P = .001; cutoff = 0.51 N·m/kg; sensitivity = 94.1%; specificity = 49.1%) for RTS prediction. Additionally, ER strength moderately correlated with the Walch-Duplay score across all examined velocities (r = 0.26-0.34; P < .05). The modified WOSI score was weakly linked to ER strength at 240 deg/s and 30 deg/s (r = 0.24-0.25; P < .05) as well as moderately linked to the limb symmetry index in ER at 60 deg/s and 30 deg/s (r = 0.30-0.38; P < .05). CONCLUSION: Isokinetic testing can act as an independent predictor of successful RTS after Latarjet surgery, with concentric ER at 240 deg/s, concentric IR at 240 deg/s, eccentric ER at 30 deg/s, and eccentric IR at 30 deg/s showing the most accuracy. Strength recovery in ER was associated with better Walch-Duplay and modified WOSI scores.

Assessing the contribution of different upper limb degrees of freedom to an unconstrained shoulder proprioception task.

For the purpose of testing shoulder joint proprioception while controlling for axioscapular muscle recruitment, a novel shoulder thoracohumeral (TH) rotation joint position sense (JPS) measurement device was designed. This device was intended to measure shoulder TH rotation, while also implicitly constraining other upper limb degrees of freedom (DOF) and minimizing cutaneous sensation. The purpose of this study was to determine whether joint motion aside from shoulder TH rotation is being captured by the shoulder JPS measurement device. Upper limb kinematics were collected from 32 participants during joint angle matching trials using the shoulder JPS measurement device. Step wise multiple regression revealed that shoulder TH rotation (ß-Humeral Rotation = 0.409, p < 0.001), and wrist deviation (ß-Wrist Deviation = 0.104, p = 0.008) both contributed a significant unique variance in the prediction of shoulder JPS measurement device rotation. Findings suggest that seated, unconstrained shoulder TH rotation JPS testing protocols in literature may be confounded by contributions from joints both proximal and distal to the shoulder. Researchers should be aware of the limitations of both constrained and unconstrained shoulder TH rotation JPS testing protocols.

Dependence of Rotator Cuff Muscle Thickness and Stiffness on Low-Level Contractions: Metrology of the Contraction Level Using Shear-Wave Imaging.

OBJECTIVE: The study aimed to investigate the effects of the level of contraction during isometric shoulder abduction at different abduction angles on muscle thickness and stiffness of the shoulder girdle in asymptomatic individuals. DESIGN: Measurement properties study. SETTING: Biomechanics and motion analysis lab. PARTICIPANTS: Twenty individuals volunteered to participate in this study. MAIN OUTCOME MEASURE: The subjects were tested for morphological and mechanical properties, expressed by thickness and stiffness of the supraspinatus tendon and muscle, and upper trapezius muscle. Moreover, acromiohumeral distance was also evaluated using B-mode ultrasound and shear-wave elastography. INTERVENTION: The thickness and stiffness of the supraspinatus and upper trapezius muscle were assessed at 3 angles of abduction (0°, 60°, and 90°) and 3 levels of contraction (0%, 10%, and 20% of the maximal voluntary isometric contraction) using ultrasonography with shear-wave imaging. Moreover, the acromiohumeral distance was measured to establish the occupation ratio during passive movement. RESULTS: The supraspinatus and upper trapezius muscle thickness and stiffness were significantly greater at 60° shoulder abduction compared with 0°, and 90° compared with 60°, as well as significantly greater at 20% maximal voluntary isometric contraction compared with 0% and 10% maximal voluntary isometric contraction. Thickness and stiffness were significantly greater in the supraspinatus compared with the upper trapezius muscle at all 3 angles of shoulder abduction for all 3 level of contractions. The acromiohumeral distance decreased significantly from 0° to 60° and from 60° to 90°. CONCLUSION: Morphological and mechanical properties of the supraspinatus and upper trapezius muscles depended on the relative level of muscle contraction and the angle of shoulder abduction.

Effects of the stretching program in male volleyball players with posterior shoulder tightness.

BACKGROUND: Stretching programs are often used to improve muscle stiffness and thereby posterior shoulder tightness (PST); however, knowledge about their effects on the viscoelastic properties of muscles and performance is limited. OBJECTIVE: The aim of this study was to investigate the effects of a six-week stretching program on the viscoelastic properties of posterior shoulder muscles, shoulder functional performance and range of motion in volleyball players with PST. STUDY DESIGN: A Randomized Controlled Trial. LEVEL OF EVIDENCE: Level II. METHODS: The study was conducted in 34 male (aged 19-26) professional volleyball players with PST. They were randomly assigned to stretching and control groups. A stretching routine (combining sleeper stretch and cross body stretch exercises) was performed in the stretching group for six weeks. Measurements were taken during the first assessment and six weeks after the initiation of stretching for the following: shoulder external/internal rotation range of motion, spike velocity, single arm seated shot-put test, and infraspinatus- posterior deltoid muscle stiffness (by shear wave elastography). RESULTS: While the stretching group had statistically better results regarding increased shoulder internal rotation (p < 0.01), spike velocity (p = 0.02) and seated single arm shot put distance (p < 0.01), stretching did not have any effect on tissue stiffness. CONCLUSIONS: A 6-week program of sleeper stretch, and cross body stretch exercises improved shoulder internal rotation and functional performance. A clinically meaningful change in muscle mechanical properties cannot be detected after a 6-week stretching program.

Comparing and characterizing scapular muscle activation ratios in males and females during execution of common functional movements.

Background: The shoulder complex relies on scapular movement controlled by periscapular muscles for optimal arm function. However, minimal research has explored scapular muscle activation ratios during functional tasks, nor how they might be influenced by biological sex. This investigation aims to characterize how sex impacts scapular muscle activation ratios during functional tasks. Methods: Twenty participants (ten females, ten males) were assessed with surface electromyography (EMG) and motion tracking during seven functional tasks. Activation ratios were calculated from normalized EMG for the three trapezius muscles and serratus anterior. Scapular angles were calculated using a YXZ Euler sequence. Two-way mixed methods ANOVAs (p < .05) were used to assess the effects of sex and humeral elevation level on ratios and angles. Results: Sex-based differences were present in the Tie Apron task, with males exhibiting higher upper trapezius/lower trapezius and upper trapezius/middle trapezius ratios than females. Males also demonstrated decreased internal rotation in this task. Other tasks showcased significant sex-based differences in scapular upward rotation but not in activation ratios. Humeral elevation generally demonstrated an inverse relationship with scapular muscle activation ratios. Conclusions: This study highlights sex-based differences in scapular muscle activation ratios during specific functional tasks, emphasizing the need to consider sex in analyses of shoulder movements. Normative activation ratios for functional tasks were provided, offering a foundation for future comparisons with non-normative groups. Further research is warranted to confirm and explore additional influencing factors, advancing our understanding of shoulder activation and movement in diverse populations.

Awareness of Visual Offset Reduces but Does Not Eliminate Joint Repositioning Errors in Virtual Reality.

The present study investigated the effect of visual offset (visuo-proprioceptive mismatch) in joint repositioning task in a three-dimensional virtual reality (VR) environment when participants were instructed to ignore vision. Twenty-five physically healthy young individuals performed shoulder joint position sense test. Repositioning accuracy was tested under two visual conditions, accurate and offset visions, and two instructions, no guidance or ignore vision. In accurate vision trials, the virtual hand of the tested limb seen in VR was congruent with where the participant placed their hand. In the offset vision condition, the virtual hand was seen 8° above or below their actual hand in the vertical plane. Repositioning error (i.e. constant error) in offset vision trials was lower when the participants were instructed to ignore vision compared to when no instruction about the visual offset was given (p < 0.001). However, constant error in offset vision trials was larger than accurate vision trials when the participants tried to ignore vision in both visual conditions (p < 0.001). Our results suggest that humans may be able to down-weight vision to some extent by conscious effort, while the influence of vision is difficult to eliminate when vision is present.

Effects of Shoulder Corrective Training Program on Pitching Loads and Sonographic Morphology in Elbow Joint in Youth Baseball Players.

ABSTRACT: Chen, P-T, Lin, Y-C, Chang, H-Y, Chiu, C-H, Chen, C-Y, Chen, P, and Lin, Y-H. Effects of shoulder corrective training program on pitching loads and sonographic morphology in elbow joint in youth baseball players. J Strength Cond Res 38(8): e440-e447, 2024-We assessed the effects of a 12-week shoulder corrective training program for shoulder flexibility and strengthening on pitching loads and sonographic morphology of the elbow joints in youth baseball players. Seventeen subjects were recruited and underwent evaluations before and after the training program. We found that following training, subjects demonstrated significantly increased ranges of shoulder internal rotation (38.9 ± 12.9° vs. 69.2 ± 10.8°, p < 0.001), external rotation (91.2 ± 14.6° vs. 107.3 ± 9.5°, p = 0.004), and horizontal adduction (21.5 ± 8.0° vs. 32.7 ± 7.3°, p = 0.002); improved strength in the shoulder internal rotators (8.7 ± 1.6 kg vs. 9.8 ± 2.1 kg, p = 0.04), external rotators (6.5 ± 1.9 kg vs. 7.5 ± 2.8 kg, p = 0.04), middle trapezius (12.7 ± 2.1 kg vs. 14.3 ± 2.4 kg, p = 0.04), and middle deltoid muscles (10.8 ± 3.3 kg vs. 14.8 ± 3.2 kg, p = 0.001); and decreased thickness of the ulnar collateral ligament (6.1 ± 0.6 mm vs. 4.8 ± 0.7 mm, p = 0.002). Although there was no substantial change in elbow torque and arm speed, significantly increased ball speed (51.2 ± 4.6 mph vs. 54.1 ± 4.5 mph, p < 0.001) and decreased arm slot (63.8 ± 11.9° vs. 53.0 ± 12.7°, p = 0.02) were observed. We suggest that adequate corrective training should be performed regularly to minimize or mitigate adverse soft tissue changes at the elbow in youth baseball players. Balanced shoulder strength and flexibility may decrease medial elbow stress during pitching. Future studies should consider the kinetic and kinematic effects of other corrective training programs on the shoulder or elbow joint during pitching.

Verification of acromion marker cluster and scapula spinal marker cluster methods for tracking shoulder kinematics: a comparative study with upright four-dimensional computed tomography.

BACKGROUND: This study validated the accuracy of the acromion marker cluster (AMC) and scapula spinal marker cluster (SSMC) methods compared with upright four-dimensional computed tomography (4DCT) analysis. METHODS: Sixteen shoulders of eight healthy males underwent AMC and SSMC assessments. Active shoulder elevation was tracked using upright 4DCT and optical motion capture system. The scapulothoracic and glenohumeral rotation angles calculated from AMC and SSMC were compared with 4DCT. Additionally, the motion of these marker clusters on the skin with shoulder elevation was evaluated. RESULTS: The average differences between AMC and 4DCT during 10°-140° of humerothoracic elevation were - 2.2° ± 7.5° in scapulothoracic upward rotation, 14.0° ± 7.4° in internal rotation, 6.5° ± 7.5° in posterior tilting, 3.7° ± 8.1° in glenohumeral elevation, - 8.3° ± 10.7° in external rotation, and - 8.6° ± 8.9° in anterior plane of elevation. The difference between AMC and 4DCT was significant at 120° of humerothoracic elevation in scapulothoracic upward rotation, 50° in internal rotation, 90° in posterior tilting, 120° in glenohumeral elevation, 100° in external rotation, and 100° in anterior plane of elevation. However, the average differences between SSMC and 4DCT were - 7.5 ± 7.7° in scapulothoracic upward rotation, 2.0° ± 7.0° in internal rotation, 2.3° ± 7.2° in posterior tilting, 8.8° ± 7.9° in glenohumeral elevation, 2.0° ± 9.1° in external rotation, and 1.9° ± 10.1° in anterior plane of elevation. The difference between SSMC and 4DCT was significant at 50° of humerothoracic elevation in scapulothoracic upward rotation and 60° in glenohumeral elevation, with no significant differences observed in other rotations. Skin motion was significantly smaller in AMC (28.7 ± 4.0 mm) than SSMC (38.6 ± 5.8 mm). Although there was smaller skin motion in AMC, SSMC exhibited smaller differences in scapulothoracic internal rotation, posterior tilting, glenohumeral external rotation, and anterior plane of elevation compared to 4DCT. CONCLUSION: This study demonstrates that AMC is more accurate for assessing scapulothoracic upward rotation and glenohumeral elevation, while SSMC is preferable for evaluating scapulothoracic internal rotation, posterior tilting, glenohumeral external rotation, and anterior plane of elevation, with smaller differences compared to 4DCT.

A portable inflatable soft wearable robot to assist the shoulder during industrial work.

Repetitive overhead tasks during factory work can cause shoulder injuries resulting in impaired health and productivity loss. Soft wearable upper extremity robots have the potential to be effective injury prevention tools with minimal restrictions using soft materials and active controls. We present the design and evaluation of a portable inflatable shoulder wearable robot for assisting industrial workers during shoulder-elevated tasks. The robot is worn like a shirt with integrated textile pneumatic actuators, inertial measurement units, and a portable actuation unit. It can provide up to 6.6 newton-meters of torque to support the shoulder and cycle assistance on and off at six times per minute. From human participant evaluations during simulated industrial tasks, the robot reduced agonist muscle activities (anterior, middle, and posterior deltoids and biceps brachii) by up to 40% with slight changes in joint angles of less than 7% range of motion while not increasing antagonistic muscle activity (latissimus dorsi) in current sample size. Comparison of controller parameters further highlighted that higher assistance magnitude and earlier assistance timing resulted in statistically significant muscle activity reductions. During a task circuit with dynamic transitions among the tasks, the kinematics-based controller of the robot showed robustness to misinflations (96% true negative rate and 91% true positive rate), indicating minimal disturbances to the user when assistance was not required. A preliminary evaluation of a pressure modulation profile also highlighted a trade-off between user perception and hardware demands. Finally, five automotive factory workers used the robot in a pilot manufacturing area and provided feedback.

Muscle and joint function in the rotator cuff deficient shoulder.

Full-thickness rotator cuff tears can lead to poor coaptation of the humeral head to the glenoid, disrupting muscle forces required for glenohumeral joint stability, ultimately leading to joint subluxation. The aim of this study was to evaluate muscle forces and glenohumeral joint translations during elevation in the presence of isolated and combined full-thickness rotator cuff tears. Eight fresh-frozen upper limbs were mounted to a computer-controlled testing apparatus that simulated joint motion by simulated muscle force application. Scapular-plane abduction was performed, and glenohumeral joint translations were measured using an optoelectronic system. Testing was performed in the native shoulder, a following an isolated tear to the supraspinatus, as well as combined tears involving the supraspinatus and subscapularis, as well as supraspinatus, infraspinatus, and teres minor. Rotator cuff tears significantly increased middle deltoid force at 30°, 60°, and 90° of abduction relative to that in the native shoulder (p < 0.05). Significantly greater superior translations were observed relative to the intact shoulder due to combined tears to the supraspinatus and infraspinatus at 30° of abduction (mean increase: 1.6 mm, p = 0.020) and 60° of abduction (mean increase: 4.8 mm, p = 0.040). This study illustrates the infraspinatus-teres minor complex as a major humeral head depressor and contributor to glenohumeral joint stability. An increase in deltoid force during abduction occurs in the presence of rotator cuff tears, which exacerbates superior migration of the humeral head. The findings may help in the development of clinical tests in rotator cuff tear diagnostics, in surgical planning of rotator cuff repair, and in planning of targeted rehabilitation.

Design and evaluation of a symmetric amplification mechanism based anthropomorphic shoulder.

Shoulder joints determine the motion range of the upper limb. Thus, the compact and well-stiffened spherical parallel mechanism (SPM) has emerged as the mainstream shoulder prosthesis design approaches. However, the SPM's moving pairs of redundant motions impose excessive constraints that limit its workspace. Therefore, amplifying the workspace of the SPM to cover the motion range required by human daily activities is a pressing problem in shoulder prosthesis design. To address this challenge, this study proposed a workspace amplification approach through the kinematic analysis of a symmetrically arranged 2 degrees of freedom (DoFs) passive mechanism, together with the designed and optimized 3-RRR SPM, to construct an anthropomorphic shoulder. The effectiveness and reliability of the proposed mechanism was verified through thorough analyses. Simulation and experiment results demonstrated that the workspace amplification mechanism could significantly increase the maximum motion match index between the shoulder prosthesis and the daily workspace of the human shoulder from only 26.3% to 94.79%, solving the problem that the traditional SPM-based prostheses cannot satisfy the motion range required by daily activities. Moreover, the proposed mechanism has the potential to amplify the workspace of most parallel mechanisms with multiple DoFs after proper modification.

Comparing shoulder proprioception, upper extremity dynamic stability, and hand grip strength in overhead athletes with and without scapular dyskinesis.

INTRODUCTION: Scapular dyskinesis is prevalent among asymptomatic athletes, particularly those involved in overhead activities, and can significantly impact their neuromuscular control. These changes may impair upper extremity function and strength, elevating the risk of injury. Therefore, it is imperative to investigate how scapular dyskinesis affects shoulder proprioception, upper extremity dynamic stability, and hand grip strength in overhead athletes. This study compared these parameters between overhead athletes with and without scapular dyskinesis. METHODS: The study included twenty asymptomatic professional overhead athletes with scapular dyskinesis and twenty without scapular dyskinesis, identified using the lateral scapular slide test. In this cross-sectional study, shoulder active joint position sense, serving as shoulder proprioception, was measured using an isokinetic dynamometer. Upper extremity dynamic stability and hand grip strength were evaluated using an upper quarter modified star excursion balance test (UQ-mSEBT) and a handheld dynamometer. RESULTS: The study found that the shoulder active joint position sense was significantly lower in the scapular dyskinesis group compared to the group without scapular dyskinesis (PExternal Rotation = 0.003, PInternal Rotation < 0.001, and PForward Flexion = 0.002). However, the two groups had no significant differences in UQ-mSEBT and hand grip strength scores. CONCLUSIONS: The results showed that scapular dyskinesis could affect the sense of shoulder active joint position among asymptomatic overhead athletes. However, it did not affect their upper extremity dynamic stability and hand grip strength.

Factors determining the short-term clinical outcomes of conservative treatment in patients with supraspinatus tear.

INTRODUCTION: To identify factors influencing the better and worse changes in the Western Ontario Rotator Cuff Index of patients undergoing conservative treatment for supraspinatus tendon tear. METHODS: The study included 30 patients with supraspinatus tendon tear who underwent conservative treatment. The average duration of intervention was 35.4 days. The Western Ontario Rotator Cuff Index, shoulder range of motion, isometric muscle strength, supraspinatus tendon thickness, thickness of the supraspinatus, infraspinatus, and teres minor muscles, and acromiohumeral interval were assessed before and after the intervention. In the statistical analyses, change in the Western Ontario Rotator Cuff Index was the dependent variable, and the amount of change in each measurement variable before and after the intervention was the independent variable. RESULTS: The average Western Ontario Rotator Cuff Index improved from 1067 at pre-treatment to 997 at post-treatment, but without a significant difference (p = 0.29). A multiple regression analysis revealed that supraspinatus tendon thickness and muscle strength in shoulder external rotation at 90° scaption had a significant effect on the change in the Western Ontario Rotator Cuff Index (R2 = 0.44, p < 0.01). CONCLUSION: Supraspinatus tendon thickness and muscle strength in shoulder external rotation at 90° scaption were important factors for the Western Ontario Rotator Cuff Index score in the early stages of conservative treatment for patients with supraspinatus tendon tear.

Exercises with the StretchPole improve shoulder joint range of motion.

The 'StretchPole' foam roller product is mainly used to loosen muscle groups and joints in the deeper layers of the body that are normally inaccessible to the human hand, and to realign the skeletal structure by lying on the pole and performing exercises. It is also used to strengthen the core, which plays an important role in postural maintenance and stability. The purpose of this study was to determine the effects of the 'Solacon' exercise routine using a StretchPole on shoulder joint range of motion. Forty healthy participants performed Solacon exercises using a StretchPole. The specific method of Solacon comprises six movements: (1) chest slide, (2) crescent, (3) cone, (4) twister, (5) shoulder alternating rotation, and (6) chin-in exercise. The joint range of motion of the bilateral shoulder joint flexion, abduction, horizontal abduction, and external rotation (1st and 2nd) were measured before and after the exercises. All measures were significantly higher after exercise compared to before exercise. Solacon exercises improve thoracic spine and scapular mobility and stretch the anterior thoracic muscle groups. The shoulder joint in the broad sense consists of the humerus, scapula, clavicle, sternum, and ribs. These in turn constitute the scapulohumeral joint, acromioclavicular joint, sternoclavicular joint, scapulothoracic joint and functional second shoulder joint. In addition, costovertebral joints and intervertebral joints are also involved because of the added motion of the ribs and the spine. We considered that the ranges of motion of shoulder joint flexion, abduction, horizontal abduction, and external rotation measured in this study were expanded.

Reliability of Dynamic Shoulder Strength Test Battery Using Multi-Joint Isokinetic Device.

This study aimed to determine the absolute and relative reliability of concentric and eccentric flexion, extension, horizontal abduction, and adduction movements of the shoulder using a functional electromechanical dynamometer (FEMD). Forty-three active male university students (23.51 ± 4.72 years) were examined for concentric and eccentric strength of shoulder flexion, extension, horizontal abduction, and horizontal adduction with an isokinetic test at 0.80 m·s-1. Relative reliability was determined by intraclass correlation coefficients (ICCs) with 95% confidence intervals. Absolute reliability was quantified by the standard error of measurement (SEM) and coefficient of variation (CV). Reliability was very high to extremely high for all movements on concentric and eccentric strength measurements (ICC: 0.76-0.94, SEM: 0.63-6.57%, CV: 9.40-19.63%). The results of this study provide compelling evidence for the absolute and relative reliability of concentric and eccentric flexion, extension, horizontal abduction, and horizontal adduction shoulder isokinetic strength tests in asymptomatic adults. The mean concentric force was the most reliable strength value for all tests.