Impingement pain affects kinematics of breast cancer survivors in work-related functional tasks

BackgroundBreast cancer survivors may encounter upper limb morbidities post-surgery. It is currently unclear how these impairments affect arm kinematics, particularly during functional task performance. This investigation examined upper body kinematics during functional tasks for breast cancer survivors and an age-matched control group.MethodsFifty women (aged 35–65) participated: 25 breast cancer survivors who had undergone mastectomy and 25 age-range matched controls. Following basic clinical evaluation, including shoulder impingement tests, motion of the torso and upper limbs were tracked during six upper limb-focused functional tasks from which torso, scapular, and thoracohumeral angles were calculated. Between-group differences were evaluated with independent t-tests (p < .05). The breast cancer group was then divided based upon impingement tests and differences between the three new groups were tested with one-way ANOVAs (p < .05).FindingsBreast cancer survivors had higher disability scores, lower range of motion, and lower performance scores. The largest kinematic differences existed between the breast cancer survivors with impingement pain and the two non-pain groups. During overhead tasks, right peak scapular upward rotation was significantly reduced (d = 0.80–1.11) in the breast cancer survivors with impingement pain. This group also demonstrated trends of decreased peak humeral abduction and internal rotation at extreme postures (d = 0.54–0.78). These alterations are consistent with kinematics considered high risk for rotator cuff injury development.InterpretationImpingement pain in breast cancer survivors influences functional task performance and may be more important to consider than self-reported disability when evaluating pain and potential injury development.     

Comparison of scapular kinematics and muscle strength between those with a positive and a negative Scapular Assistance Test

BackgroundThe Scapular Assistance Test was suggested to directly assess the influence of scapular motion on pain and indirectly measure the function of the scapular rotators. However, it is still not clear if individuals with a positive Scapular Assistance Test actually present changes in scapular motion and muscle strength. This study compared scapular kinematics and muscle strength between those with a positive Scapular Assistance Test and those with a negative Scapular Assistance Test.MethodsFifty individuals with shoulder pain were randomly allocated to: positive (n = 25) or negative Scapular Assistance Test (n = 25) group. Scapular kinematics was measured during elevation and lowering of the arm. Strength of the serratus anterior and lower trapezius was also measured. Two-way analysis of variance was used to compare kinematics between groups. Unpaired Student's t-test and Mann-Whitney test were used to compare strength of serratus anterior and lower trapezius, respectively.FindingsThere were no differences (P > 0.05) in scapular internal rotation and upward rotation between both groups. For scapular tilt, there was group main effect (P < 0.05) during elevation and lowering of the arm, whereas the positive Scapular Assistance Test group presented greater scapular anterior tilt. There was no difference (P > 0.05) in strength between groups.InterpretationIndividuals with a positive Scapular Assistance Test are more likely to present decreased scapular posterior tilt in those with shoulder pain. Strength of the scapular muscles seems to be same in those with a positive and a negative Scapular Assistance Test.     

Shoulder Kinematics of Axillary Web Syndrome in Women Treated for Breast Cancer

ObjectiveTo better understand how the shoulder moves in breast cancer survivors with axillary web syndrome (AWS), we compared 3-dimensional (3D) shoulder kinematics during shoulder elevation among breast cancer survivors with and without AWS 5 years postoperatively. Although research consistently shows decreased shoulder range of motion with AWS, we do not understand the underlying biomechanics.DesignNested case control study.SettingUniversity Academic Breast Center.ParticipantsTwenty-five women who had surgery 5 years previously for unilateral breast cancer with the removal of at least 1 lymph node participated in this study (N=25). Twelve participants had AWS; 13 women did not have AWS.InterventionsNot applicable.Main Outcome MeasuresThree-dimensional shoulder kinematic data during shoulder forward flexion, scapular plane abduction, and coronal plane abduction were collected using 3D electromagnetic motion tracking. Kinematic data were extracted at 30°, 60°, 90°, and 120° of arm elevation for scapular upward rotation, internal rotation, and posterior tilt as well as for glenohumeral external rotation.ResultsWomen with AWS demonstrated 15.2° less scapular upward rotation at 120° humerothoracic elevation (95% confidence interval [-25.2, -5.2], P=.005), regardless of plane. No significant between-group differences were found for any other angle of scapular upward rotation, nor for scapular internal rotation, scapular posterior tilt, or glenohumeral axial rotation at any angle.ConclusionsFive years after surgery for breast cancer, women diagnosed with AWS have altered scapulohumeral kinematics that may place them at an increased risk of shoulder pain based on existing kinematic literature in healthy cohorts. This information can help guide rehabilitation programs for breast cancer survivors to facilitate pain-free upper extremity function after treatment.     

Interaction of scapular dyskinesis with hand dominance on three-dimensional scapular kinematics

IntroductionThis study aimed to evaluate the effect of scapular dyskinesis and its interaction with hand dominance and humerothoracic angles on three-dimensional scapular kinematics in asymptomatic individuals in all planes of arm motion.MethodsForty-five asymptomatic participants, seventeen men and twenty-eight women, were separated into two groups: with (n = 22) and without scapular dyskinesis (n = 23) according to the Yes/No classification. Scapular kinematic data of dominant and non-dominant sides in both groups were measured with an electromagnetic tracking device during arm elevation and lowering phases in scapular, frontal and sagittal planes. A linear mixed model of covariance adjusted for age and BMI was used, which included hand dominance (dominant and non-dominant), group (with and without scapular dyskinesis), angles (30°, 60°, 90°, and 120°), and the interaction effect (group × hand dominance × humerothoracic angle).ResultsThere was a significant interaction effect on scapular anterior tilt and upward rotation in the sagittal plane, and for internal rotation and anterior tilt in the frontal and scapular planes. The effects of hand dominance on three-dimensional scapular kinematics, as increased anterior tilt, internal rotation and upward rotation, were greater in individuals without scapular dyskinesis.ConclusionThe effects of dominant side as increased upward rotation, internal rotation, and anterior tilt at higher humerothoracic angles for all planes of arm motion, were greater in individuals without scapular dyskinesis. Our findings may assist the scapular assessment which in individuals without scapular dyskinesis, bilaterally, possible between side differences in the scapular motions may be related to a dominance effect.     

Scapular asymmetry in participants with and without shoulder impingement syndrome; a three-dimensional motion analysis

BackgroundThis study analyzed the dynamic three-dimensional scapular kinematics and scapular asymmetry in participants with and without shoulder impingement syndrome.MethodsTwenty-nine participants with shoulder impingement syndrome, have been suffering from unilateral shoulder pain at the dominant arm lasting more than six weeks and thirty-seven healthy controls participated in the study. Scapular kinematics was measured with an electromagnetic tracking device during shoulder elevation in the sagittal plane. Data for bilateral scapular orientation were analyzed at 30°, 60°, 90°, and 120° of humerothoracic elevation and lowering. The symmetry angle was calculated to quantify scapular asymmetry throughout shoulder elevation.FindingsStatistical comparisons indicated that the scapula was more downwardly rotated (p < 0.001) and anteriorly tilted (p = 0.005) in participants with shoulder impingement syndrome compared to healthy controls. Side-to-side comparisons revealed that the scapula was more anteriorly tilted on the involved side of participants with shoulder impingement syndrome (p = 0.01), and the scapula was rotated more internally (p = 0.02) and downwardly (p = 0.01) on the dominant side of healthy controls. Although there were side-to-side differences in both groups, symmetry angle calculation revealed that the scapular movement was more asymmetrical for scapular internal and upward rotation in individuals with shoulder impingement syndrome when compared with healthy controls (p < 0.05).InterpretationThe findings of the study increase our knowledge and understanding of scapular alterations in symptomatic and asymptomatic populations, which creates biomechanical considerations for shoulder assessment and rehabilitation.     

Shoulder dysfunction assessment: self-report and impaired scapular movements

BACKGROUND AND PURPOSE: Shoulder dysfunction is common in various patient populations. This investigation was performed to assess shoulder dysfunction with self-report and performance-based functional measures. SUBJECTS: Fifty men (25 with shoulder dysfunction and 25 without shoulder dysfunction) participated in this study. METHODS: Self-report functional disabilities were assessed with the Flexilevel Scale of Shoulder Function (FLEX-SF), and electromagnetic tracking sensors were used to monitor 3-dimensional scapular movements during 4 functional tasks. RESULTS: Relative to the control group, the group with shoulder dysfunction showed significant alterations in scapular movements (averages of 6.9 degrees less posterior tipping, 5.7 degrees less upward rotation, and 2.3 cm more elevation). Scapular kinematics correlated significantly (r) with the Self-report FLEX-SF measure during functional tasks (posterior tipping = .454 to .712, upward rotation = .296 and .317, and elevation = -.310). DISCUSSION AND CONCLUSION: Functional disabilities were identified with self-report and performance-based functional measures. The inadequate scapular posterior tipping and scapular upward rotation as well as the excessive elevation may have implications in planning intervention strategies for people with shoulder dysfunction.     

Scapular kinematics and impairment features for classifying patients with subacromial impingement syndrome

Subacromial impingement syndrome (SAIS), which is associated with pain and a loss of function, has a high occurrence in the physically active population. Not all patients respond positively to treatment. Classifying patients can improve decision-making. The scapular kinematic and clinical impairments can aid in classifying the patients who are more likely to respond to physical therapy treatment. Thirty-three subjects (males, 20–33 years) presenting SAIS were studied to determine altered scapular kinematics and clinical impairments. Three measurements were collected: (1) three-dimensional scapular kinematics during performing functional tasks; (2) impairment outcomes of range of motion and muscle force; and (3) self-reported measurements of pain, satisfaction, and function. All patients received 6-week (2 times per week) physical therapy treatment. Improvement with treatment was determined using the Global Rating of Change Scale. Scapular kinematics and clinical impairments were first identified by t-test in predicting improvement and then combined into a multivariate prediction method. A prediction method with three variables (Flexilevel Scale of Shoulder Function score < 41, muscle power of serratus anterior < 27.4% body weight, degree of scapular internal rotation at 30° shoulder elevation during descending arm phase in unloaded condition < 0.7°) were identified. It appears that scapular kinematics and impairment features can be used to classify subjects with SAIS in addition to self-report. Prospective validation of the proposed prediction method requires further investigation.     

Effect of shoulder pain on shoulder kinematics during weight-bearing tasks in persons with spinal cord injury

Nawoczenski DA, Riek LM, Greco L, Staiti K, Ludewig PM. Effect of shoulder pain on shoulder kinematics during weight-bearing tasks in persons with spinal cord injury.ObjectiveTo assess 3-dimensional scapulothoracic and glenohumeral kinematics between subjects with spinal cord injury and disease (SCI/D) with and without shoulder pain during a weight-relief raise and transfer task.DesignCase-control, repeated-measures analysis of variance.SettingMovement analysis laboratory.ParticipantsSubjects (N=43; 23 with clinical signs of impingement and 20 without) between 21 and 65 years of age, at least 1 year after SCI/D (range, 1–43y) resulting in American Spinal Injury Association Impairment Scale T2 motor neurologic level or below, and requiring the full-time use of a manual wheelchair.InterventionsWeight-relief raises and transfer tasks.Main Outcome MeasuresAn electromagnetic tracking system acquired 3-dimensional position and orientation of the thorax, scapula, and humerus. Dependent variables included angular values for scapular upward and downward rotation, posterior and anterior tilt, and internal and external rotation relative to the thorax, and glenohumeral internal and external rotation relative to the scapula. The mean of 3 trials was collected, and angular values were compared at 3 distinct phases of the weight-relief raise and transfer activity. Comparisons were also made between transfer direction (lead vs trail arm) and across groups.ResultsKey findings include significantly increased scapular upward rotation for the pain group during transfer (P=.03). Significant group differences were found for the trailing arm at the lift pivot (phase 2) of the transfer, with the pain group having greater anterior tilt (mean difference ± SE, 5.7°±2.8°). The direction of transfer also influenced kinematics at the different phases of the activity.ConclusionsPotentially detrimental magnitude and direction of scapular and glenohumeral kinematics during weight-bearing tasks may pose increased risk for shoulder pain or injury in persons with SCI/D. Consideration should be given to rehabilitation strategies that promote favorable scapular kinematics and glenohumeral external rotation.     

Three-dimensional scapular motion during arm elevation is altered in women with fibromyalgia

Background

The core feature of fibromyalgia is pain, which may play a role in various mechanisms that might lead to alterations in shoulder kinematics. Alterations in muscle activity and presence of tender points in the shoulder girdle have already been described in this population; however there is lack of evidence on three-dimensional scapular motion in women with fibromyalgia.

Methods

Forty women with fibromyalgia and 25 healthy women (control group) matched in terms of age, weight and height, took part in this study. Three-dimensional scapular kinematics of the dominant arm were collected during elevation and lowering of the arm in the sagittal and scapular planes. Pain was evaluated by the Visual Analogue Scale and the Numerical Pain Rating Scale. Group comparisons were performed with one-way ANOVA for pain and two-way ANOVA for the kinematic variables (scapular internal/external rotation, upward/downward rotation and anterior/posterior tilt), with group and humeral elevation angle as categorical factors. Significance level was set at P < 0.05.

Findings

Fibromyalgia women presented higher pain scores (P < 0.001) than the control group. Fibromyalgia women also presented greater scapular upward rotation (P < 0.001, both planes) and greater scapular posterior tilt (P < 0.001, both planes) than the control group.

Interpretation

Women with fibromyalgia present greater scapular upward rotation and posterior tilt in the resting position and during arm elevation and lowering of the arm in sagittal and scapular planes. These alterations may be a compensatory mechanism to reduce pain during arm movement.     

Comparison of scapular kinematics between elevation and lowering of the arm in the scapular plane

Objective. To compare scapular orientation during both the concentric (elevation) and eccentric (lowering) phases of scapular plane abduction in subjects with and without shoulder impingement.

Design. Mixed model analysis of variance with one between-subjects factor (group) and within-subjects factors of phase, humeral angle, and trial.

Background. Abnormal scapular kinematics have been identified in shoulder impingement patients during the concentric phase of arm elevation, and under static conditions. Because abnormal scapular motion is observed clinically during the eccentric phase of arm elevation, analysis of this phase of motion is warranted.

Methods. Twenty-six symptomatic and 26 healthy subjects performed five repetitions of humeral scapular plane abduction. An electromagnetic tracking device described three-dimensional scapular kinematics during arm elevation and lowering. Angular values for scapular anterior/posterior tipping in the sagittal plane, upward/downward rotation in the scapular plane, and internal/external rotation in the transverse plane were calculated. Scapular orientation relative to the thorax at humeral angles of 40°, 60°, 80°, 100°, and 120° was statistically tested for effects of phase and trial, or for interactions of phase with group or humeral angle.

Results. Internal rotation was significantly increased in the eccentric phase for both groups at the 100° angle (P<0.05) and for the symptomatic group only at the 120° angle (P<0.05). Scapular anterior tipping was significantly decreased during the eccentric phase in both groups at the 80° (P<0.001), 100° (P<0.0001), and 120° (P<0.0001) angles.

Conclusions. Small but statistically significant differences in scapular tipping and internal rotation during the eccentric phase of arm elevation were identified at higher humeral angles in both subject groups, while no significant phase differences for scapular upward rotation or for scapular variables at lower humeral angles were found. Averaged across phases, the symptomatic group demonstrated significant reductions in upward rotation at lower humeral elevation angles, and significant increases in anterior tipping at higher elevation angles as compared to the healthy group.

Relevance Normal and abnormal scapular kinematics during varying types of motion need to be understood in order to optimally design rehabilitation programs for individuals with impingement syndrome.     

In vivo measurement of distance between scapular neck and polyethylene insert during active external rotation in shoulders with Grammont type reverse prosthesis

BackgroundScapular notching is a frequently observed complication after reverse shoulder arthroplasty. Impingement of the humeral plastic insert against the scapular neck is believed to be the cause of notching. There have been no in vivo studies that analyzed the positional relationship between the scapular neck and humeral insert. The purpose of this study was to measure the distance between the scapular neck and insert in shoulders with Grammont-type prostheses during active external rotation at the side.MethodsEighteen shoulders with Grammont-type prostheses were enrolled in this study. There were 13 males and 5 females, and the mean age at surgery was 74 years (range, 63–91). Fluoroscopic images were recorded during active external rotation at the side from maximum internal to external rotation at an average of 14 months (range, 7–24) after surgery. Implant kinematics were determined with three-dimensional models of the implants and fluoroscopic images using model-image registration techniques. Based on the implant kinematics, the closest distance between the scapular neck and insert was computed at each 5° increment of glenohumeral internal/external rotation.ResultsMean glenohumeral abduction during rotation was 17°–22°. The mean distance between the neck and insert was approximately 1 mm throughout the activity. The separation distance tended to narrow with arm external rotation, but the change was not significant.InterpretationThe small distance between the scapular neck and insert in early post-operative reverse shoulder arthroplasty patients may be associated with the high incidence of scapular notching in Grammont-type prostheses.     

Immediate effect of scapula-focused exercises performed with kinematic biofeedback on scapular kinematics in individuals with subacromial pain syndrome

BackgroundGiven the changes in the patterns of muscular activation and scapular movement in individuals with subacromial pain syndrome, the use of neuromuscular training has been considered in rehabilitation protocols. There is currently no evidence of the effects of the use of three-dimensional (3D) kinematic biofeedback on individuals with subacromial pain syndrome. This study aimed to determine the immediate effect of scapular motor control exercises using 3D kinematic biofeedback on the scapular kinematics, inter-segment coordination and pain of individuals with subacromial pain syndrome.MethodThe kinematics of the scapulothoracic joint of 26 subjects with subacromial pain syndrome were assessed in the movement arm elevation and lowering in the sagittal plane before and after performance of three scapula-focused exercises using kinematic biofeedback. The individuals were familiarized with the selected exercises to acquire a greater scapular posterior tilt, while kinematic biofeedback, with visual and auditory stimuli, was used in real time. Scapular kinematics, pain, and subjective perception of exertion were the pre- and post-test measures.FindingsIn the movement of arm elevation and lowering, no differences were found in scapular tilt and on coordination between the segments pre- and post-test and the effect size was considered small.InterpretationOur results demonstrate that the performance of scapula-focused exercises using kinematic biofeedback does not cause immediate changes in the magnitude of scapular movement. However, inter-segmental coordination showed evidence of changes for scapular tilt in the lowering of the arm and internal rotation in the elevation and the lowering of the arm in individuals with subacromial pain syndrome.     

Scapular-focused exercise treatment protocol for shoulder impingement symptoms: Three-dimensional scapular kinematics analysis

BackgroundThe present study aimed to describe the effects of a periscapular strengthening and neuromuscular training protocol in three-dimensional scapular kinematics and resting positioning in participants with shoulder impingement symptoms. Self-reported function was also evaluated.MethodThe study group comprised 50 subjects with shoulder impingement syndrome (control group, n = 25; treatment group, n = 25). The treatment group underwent 8 weeks of neuromuscular training and periscapular strengthening. Scapular kinematics was measured using an electromagnetic tracking device, and the Brazilian version of the Shoulder Pain and Disability Index (SPADI-Br) questionnaire was carried out before and after the treatment.FindingsIn the resting position, treated subjects had lower (p < 0.01) internal rotation of the scapula compared to the control group, with a large effect size (2.4). On the coronal plane, the treated group had less scapular upward rotation (p < 0.01) and less internal rotation (p < 0.05), with a medium effect size. On the sagittal plane, the treated group had less internal rotation (p < 0.01), less upward rotation (p < 0.05), and less scapular anterior tilt (p < 0.01), with a medium effect size. On the scapular plane, a reduction in upward rotation (p < 0.01) after the intervention was observed, with a large effect size. Moreover, a reduction in the total SPADI-Br score was found, with a mean difference of 32.4 [24.4; 40.4] points (p < 0.01) after the implementation of the protocol and a large effect size (2.0).InterpretationThe results provide biomechanical support for the clinical rationale for indicating therapeutic exercises focused on the periscapular muscles to improve scapular dynamics.     

The specificity of fatiguing protocols affects scapular orientation: Implications for subacromial impingement

Background

Shoulder impairments are often associated with altered scapular kinematics. As muscles control scapular movement, functionally altering muscle performance through fatigue may produce scapular kinematics that mimic those of injured patients. The aim of this study was to examine if changes in scapular tilt, rotation and pro/retraction following two different upper extremity fatiguing protocols have any implications with respect to subacromial impingement.

Methods

Scapular orientation was monitored during posturally constrained static holds (at 0°, 45° and 90° of humeral elevation) before and after two fatiguing protocols, one global and one local. Both protocols are associated with producing changes in shoulder skeletal arrangement.

Findings

Following the global fatiguing protocol, there was significantly more scapular posterior tilt (P < 0.01) and upward rotation (P < 0.02), particularly at 90° humeral elevation. No changes in scapular orientation occurred following the local fatiguing protocol.

Interpretation

Scapular orientation changes following muscle fatigue acted to increase the subacromial space. Thus, the rotator cuff muscles, not the scapular stabilizers, have more influence on actively preventing mechanical subacromial impingement. The lack of evidence of reduction of the subacromial space thus implicates superior humeral head translation as a more likely primary mechanism of the initiation of subacromial impingement.     

Examining upper limb kinematics and dysfunction of breast cancer survivors in functional dynamic tasks

BackgroundComorbidities within the breast cancer population can reduce quality of life. Current breast cancer survivor upper limb kinematic strategies unfortunately lack robust connection with performing important activities of daily living.MethodsAccordingly, fifty breast cancer survivors performed 88 dynamic tasks (divided into range of motion-reach, range of motion-rotate, activity of daily living, and work tasks). Humerothoracic and scapulothoracic angles were extracted from motion capture data. Bilateral differences existed for range of motion, and maximal and minimal scapulothoracic and humerothoracic angles.FindingsGenerally, the affected side used less range of motion across task types. Humerothoracic angles on the affected side experienced 6.7° less range of motion in plane of elevation in range of motion-reach (p < 0.01), 2.3° less elevation angle range of motion in range of motion-rotate (p = 0.01), and 7.1° more internal rotation range of motion in range of motion-rotate (p < 0.01). Scapulothoracic angles on the affected side had 2° more anterior/posterior tilt range of motion in work tasks (p = 0.03), 3.4° less maximal protraction in activity of daily living tasks (p = 0.01), and 3.5° less minimum downward rotation in range of motion-rotate (p < 0.01).InterpretationA reduced range of motion on the affected side suggests the breast cancer population had less varied movement strategies, keeping movements in narrower ranges to avoid disability, pain, or subacromial impingement. This investigation produced an unprecedentedly diverse collection of three-dimensional humerothoracic and scapulothoracic kinematics for a breast cancer population. Documentation of physical capability, dysfunction, and adaptive strategies is a crucial step towards developing targeted strategies for enhancing functional recovery in breast cancer survivors.     

Between-Day Reliability of Scapular Locator for Measuring Scapular Position During Arm Elevation in Asymptomatic Participants

ObjectiveThe aim of this study was to assess the between-day reliability of the scapular locator for measuring scapular rotations during arm elevation in patients without shoulder pain/conditions/disorders.MethodsTwenty-three asymptomatic individuals were measured during 2 sessions separated by 24 hours. One observer measured scapular position with a scapular locator while participants held their arms at 30°, 60°, 90°, and 120° elevation in the scapular plane. Three trials were performed for each arm position.ResultsAt 30°, between-day intraclass correlation coefficients (ICCs) for all scapular rotations were poor (ICC 0.10-0.40). At higher arm elevations (60°, 90°, and 120°), ICCs ranged from 0.73 to 0.93 for scapular upward rotation, 0.80 to 0.87 for posterior tilt, and 0.37 to 0.62 for scapular internal rotation. For all scapular rotations, the standard error of measurement was less than 6°, and the smallest detectable difference ranged from 11° to 18°.ConclusionThe findings indicate good to excellent reliability for measuring scapular upward/downward rotation and anterior/posterior tilt between 60° and 120° of shoulder elevation in the scapular plane. However, low reliability was found for all scapular rotations at 30° elevation, and for scapular internal rotation at higher arm elevation.     

Effects of muscle fatigue on 3-dimensional scapular kinematics

OBJECTIVE: To determine the effects of fatigue during an external rotation task on 3-dimensional scapular kinematics. DESIGN: A single-group, pretest-posttest measurement design. SETTING: Research laboratory. PARTICIPANTS: Thirty healthy subjects. INTERVENTIONS: Not applicable.Main Outcome Measures: Three-dimensional scapular kinematics were recorded with a Polhemus magnetic tracking device during arm elevation in the scapular plane. RESULTS: There was a significant fatigue effect for all scapular rotations in the early to middle phases of humeral elevation. Significantly less posterior tilting (up to 90 degrees of elevation), external rotation (up to 120 degrees of elevation), and upward rotation (up to 60 degrees of elevation) were observed. Additionally, there were fair to good correlations (r range,.39-.60) between the changes in scapular posterior tilting and the amount of muscle fatigue. CONCLUSIONS: Fatigue in shoulder external rotation altered the scapular resting position and the movement of posterior tilting in the early range during arm elevation in the scapular plane. Observed changes in scapular kinematics may affect the amount of area in the subacromial space and facilitate impingement. Data regarding changes produced by fatigue of the external rotators may also help with the development of a model of diminished rotator cuff function.     

Functional activities characteristics of shoulder complex movements: Exploration with a 3-D electromagnetic measurement system

The high prevalence of shoulder-related dysfunction has focused increased attention on functional activity assessment. This study (1) tested the reliability of three-dimensional shoulder complex movements during four functional tasks representing different levels of task difficulty, (2) characterized the four functional tasks, and (3) examined the relationships between age and shoulder movements. Twenty-five asymptomatic subjects, all veterans aged 30-82, performed the four functional tasks. Good within-session reliability was found (movement pattern: similarity index = 0.81 to 0.97, peak values: intraclass correlation coefficients = 0.88 to 0.99). The raising arm to overhead height task (hard task) placed the greatest demand on scapular motions and humeral elevation (p < 0.005). During the functional tasks, significant correlations existed between age and scapular tipping, humeral elevation, and scapular upward rotation (r = -0.62 to 0.50, p < 0.05). Correlation results indicated that elderly subjects have a greater potential for serratus anterior muscle weakness and shoulder capsule tightness.