The role of physical arm function and demographic disparities in breast cancer survivors' ability to return to work.

PURPOSE: Ability to return to work (RTW) is an important aspect of breast cancer that is limited for many survivors. With 90% survivorship in the USA, it is imperative that focus shifts toward the improvement of physical arm function to improve survivors' ability to RTW. This narrative review discusses the role of physical arm function and demographic disparities in breast cancer survivor RTW. METHODS: Literature on physical function, arm function, and demographic disparities following breast cancer treatment and their implications for RTW is discussed. RESULTS: The ability to RTW is a key component of recovery for breast cancer survivors, but challenges and inequalities persist. Treatment effects can induce and prolong functional disability, affecting survivors' ability to RTW. These effects may be compounded for survivors whose occupation requires physical arm function. The RTW landscape, including the occupations survivors have, the physical function required for job tasks, and availability of workplace accommodations, is also unclear. Additional demographic disparities (e.g., income, live in rural area) exist, but the extent to which these factors influence RTW is not well understood. More work is needed to understand the compounded impact of treatment effects, demographic disparities, and occupational factors on RTW. Multidisciplinary rehabilitation that includes occupational counseling and exercise is a promising approach, but widespread adoption in the US healthcare model presents an ongoing challenge. Areas for further research are highlighted. CONCLUSION: There is an incomplete understanding of the effects of treatment on physical arm function and the role of demographic disparities on breast cancer survivor RTW.

The influence of mastectomy and reconstruction on residual upper limb function in breast cancer survivors.

PURPOSE: Breast cancer survivorship is common (90% of women survive 5 or more years), but many women are not able to return to full function and well-being after treatment due to functional limitations, persistent pain, and inability to perform daily activities. Since each surgical reconstructive option (e.g., autologous tissue flaps versus implants) can impact shoulder and arm function differently, it is important to understand how shoulder and upper limb strength, mobility, and function are influenced by the type of surgical intervention. Efforts can then focus on prehabiliation strategies to prevent the onset of limitations and on developing rehabilitation protocols that directly target shortcomings. METHODS: The current paper presents a review summarizing how shoulder and upper limb function may be affected by surgical mastectomy and breast reconstruction. RESULTS: Mastectomy and breast reconstruction with implants or autologous tissues present different functional outcomes for patients. Each surgical procedure is associated with unique sequelae derived from the tissues and procedures associated with each surgery. Characterizing the specific functional outcomes associated with each surgical approach will promote the development of targeted rehabilitation strategies that can be implemented into a multidisciplinary treatment planning pathway for breast cancer patients. CONCLUSIONS: Surgical treatments for breast cancer, including mastectomy and breast reconstruction, can have negative effects. Focused efforts are needed to better understand treatment-specific effects so that targeted rehabilitation can be developed to improve patient function, QoL, and ability to return to work and life activities post-breast cancer.

Scapular Kinematics by Sex Across Elevation Planes.

Scapular kinematics are important indicators of dyskinesis, often suggesting underlying shoulder pathology, but the influence of sex is unknown. This study's objective was to examine scapular kinematics in healthy males and females. Positions of surface-mounted reflective markers were tracked during arm elevation movements in 0°/30°/40°/60°/90°/120° planes. Scapulothoracic rotations (protraction/retraction, medial/lateral rotation, posterior/anterior tilt) were calculated. ANOVA analysis evaluated main and interaction effects of sex, plane, phase, and elevation angle. Males and females had similar protraction/retraction and medial/lateral rotation kinematics; mean sex-related peak angle differences were 2.5°, 1.8° (raise [concentric]), respectively, and 2.9°, 2.7° (lower [eccentric]), respectively. Largest sex differences for mean peak angle occurred for posterior/anterior tilt at higher elevation angles (raise, 8.4°; lower, 8.5°). Elevation, plane, and phase were main effects for all scapular rotations (P < .001). Sex was not a main effect for any rotations. Sex × elevation interactions influenced protraction/retraction (P < .001) and posterior/anterior tilt (P < .001). Sex × plane (P ≤ .01) and sex × phase (P ≤ .002) interactions influenced all rotations. Lower posterior tilt for females compared to males at higher elevation angles could relate to higher female shoulder pathology incidence. Sex, plane, and phase are necessary components of uninjured scapular kinematics. Sex-specific differences provide insight into potential shoulder pathology etiology. These data provide a benchmark to assess pathological populations.

Shoulder Strength Requirements for Upper Limb Functional Tasks: Do Age and Rotator Cuff Tear Status Matter?

Understanding upper limb strength requirements for daily tasks is imperative for early detection of strength loss that may progress to disability due to age or rotator cuff tear. We quantified shoulder strength requirements for 5 upper limb tasks performed by 3 groups: uninjured young adults and older adults, and older adults with a degenerative supraspinatus tear prior to repair. Musculoskeletal models were developed for each group representing age, sex, and tear-related strength losses. Percentage of available strength used was quantified for the subset of tasks requiring the largest amount of shoulder strength. Significant differences in strength requirements existed across tasks: upward reach 105° required the largest average strength; axilla wash required the largest peak strength. However, there were limited differences across participant groups. Older adults with and without a tear used a larger percentage of their shoulder elevation (p < .001, p < .001) and external rotation (p < .001, p = .017) strength than the young adults, respectively. Presence of a tear significantly increased percentage of internal rotation strength compared to young (p < .001) and uninjured older adults (p = .008). Marked differences in strength demand across tasks indicate the need for evaluating a diversity of functional tasks to effectively detect early strength loss, which may lead to disability.

Assessments of Fatty Infiltration and Muscle Atrophy From a Single Magnetic Resonance Image Slice Are Not Predictive of 3-Dimensional Measurements.

PURPOSE: To (1) determine whether standard clinical muscle fatty infiltration and atrophy assessment techniques using a single image slice for patients with a rotator cuff tear (RCT) are correlated with 3-dimensional measures in older individuals (60+ years) and (2) to determine whether age-associated changes to muscle morphology and strength are compounded by an RCT. METHODS: Twenty older individuals were studied: 10 with an RCT of the supraspinatus (5 men and 5 women) and 10 matched controls. Clinical imaging assessments (Goutallier and Fuchs scores and cross-sectional area ratio) were performed for participants with RCTs. Three-dimensional measurements of rotator cuff muscle and fat tissues were obtained for all participants using magnetic resonance imaging (MRI). Isometric joint moment was measured at the shoulder. RESULTS: There were no significant associations between single-image assessments and 3-dimensional measurements of fatty infiltration for the supraspinatus and infraspinatus muscles. Compared with controls, participants with RCTs had significantly increased percentages of fatty infiltration for each rotator cuff muscle (all P ≤ .023); reduced whole muscle volume for the supraspinatus, infraspinatus, and subscapularis muscles (all P ≤ .038); and reduced fat-free muscle volume for the supraspinatus, infraspinatus, and subscapularis muscles (all P ≤ .027). Only the teres minor (P = .017) fatty infiltration volume was significantly greater for participants with RCTs. Adduction, flexion, and external rotation strength (all P ≤ .021) were significantly reduced for participants with RCTs, and muscle volume was a significant predictor of strength for all comparisons. CONCLUSIONS: Clinical scores using a single image slice do not represent 3-dimensional muscle measurements. Efficient methods are needed to more effectively capture 3-dimensional information for clinical applications. Participants with RCTs had increased fatty infiltration percentages that were likely driven by muscle atrophy rather than increased fat volume. The significant association of muscle volume with strength production suggests that treatments to preserve muscle volume should be pursued for older patients with RCTs. LEVEL OF EVIDENCE: Level II, diagnostic study, with development of diagnostic criteria on the basis of consecutive patients with universally applied reference gold standard.

The spatial dependency of shoulder muscular demands during upward and downward exertions.

Lifting and lowering are common occupational tasks contributing to shoulder injury risk. Quantifying task interaction with physical demand can precipitate better workstation designs. Nineteen university-aged males performed one-handed, submaximal upward/downward manual force exertions at 70 hand locations; unilateral electromyography (EMG) of 14 muscles was recorded. EMG across planes was evaluated with ANOVA. Predictive equations for muscle activity throughout the reach envelope were developed with stepwise regression. Total muscle activity (sum of individual muscle activity) was most sensitive to vertical hand location for upward exertions, where activation at superior locations was 192% of values for inferior locations. For upward exertions, activation differences for hand location occurred along all anatomical axes, and along anterior/posterior and superior/inferior axes for downward exertions. Predictive equations were non-linear, reflecting complex muscular demand with three-dimensional hand location. This work details foundational exposure data for lifting/lowering exertions. Results are applicable to workstation design to minimise occupational shoulder muscular demands. Practitioner Summary: Lifting and lowering in the workplace contribute to shoulder injury risk. Shoulder muscle activity magnitudes revealed a dependence on three-dimensional hand location in the reach envelope for a defined hand force. This information can inform evidence-based workstation designs that reduce shoulder muscular demands for numerous materials handling scenarios.

Upper Limb Strength and Muscle Volume in Healthy Middle-Aged Adults.

Our purpose was to characterize shoulder muscle volume and isometric moment, as well as their relationship, for healthy middle- aged adults. Muscle volume and maximum isometric joint moment were assessed for 6 functional muscle groups of the shoulder, elbow, and wrist in 10 middle-aged adults (46–60 y, 5M, 5F). Compared with young adults, shoulder abductors composed a smaller percentage of total muscle volume (P = .0009) and there was a reduction in shoulder adductor strength relative to elbow flexors (P = .012). We observed a consistent ordering of moment-generating capacity among functional groups across subjects. Although total muscle volume spanned a 2.3-fold range, muscle volume was distributed among functional groups in a consistent manner across subjects. On average, 72% of the variation in joint moment could be explained by the corresponding functional group muscle volume. These data are useful for improved modeling of upper limb musculoskeletal performance in middle-aged subjects, and may improve computational predictions of function for this group.

Focused ultrasound as an alternative to dry needling for the treatment of tendinopathies: A murine model.

Tendinopathies account for 30% of 102 million annual musculoskeletal injuries occurring annually in the United States. Current treatments, like dry needling, induce microdamage to promote healing but produce mixed success rates. Previously, we showed focused ultrasound can noninvasively create microdamage while preserving mechanical properties in ex vivo murine tendons. This present study compared growth factor, histological, and mechanical effects after focused ultrasound or dry needling treatments in an in vivo murine tendon injury model. Partial Achilles tenotomy was performed in 26 rats. One-week postsurgery, tendons were treated with focused ultrasound (1.5 MHz, 1-ms pulses at 10 Hz for 106 s, p+ = 49 MPa, p- = 19 MPa) or dry needling (30 G needle, 5 fenestrations over 20 s) and survived for 1 additional week. Blood was collected immediately before and after treatment and before euthanasia; plasma was assayed for growth factors. Treated tendons and contralateral controls were harvested for histology or mechanical testing. No differences were found between treatments in release of insulin growth factor 1 and transforming growth factor beta; vascular endothelial growth factor A concentrations were too low for detection. Histologically, focused ultrasound and dry needling tendons displayed localized fibroblast infiltration without collagen proliferation with no detectable differences between treatments. Mechanically, stiffness and percent relaxation of dry needling tendons were lower than controls (p = 0.0041, p = 0.0441, respectively), whereas stiffness and percent relaxation of focused ultrasound tendons were not different from controls. These results suggest focused ultrasound should be studied further to determine how this modality can be leveraged as a therapy for tendinopathies.

Risk Reduction of Concussion in Athletes: Do Neck Size or Neck Strength Make a Difference?

ABSTRACT: Medical provider's ability to detect, diagnose, and treat sport-related concussion has greatly improved in recent years. Although more is known about the biomechanical forces involved in concussion, it is still uncertain whether there are preventative measures athletes can take to prevent a sport-related concussion from occurring. The objective of this review was to determine if either neck size or neck strength is related to a decreased risk of sustaining a sport-related concussion. A literature review was conducted on Google Scholar and Ovid MEDLINE for pertinent articles. Findings indicate that isometric neck strength, but not neck size, has been shown to be a predictor for sport-related concussion prevention. Formal neck strengthening programs are feasible and lead to decreased sport-related concussion risk. Additionally, there may be greater opportunity to increase neck strength in amateur athletes compared to professional. In conclusion, cervical strengthening programs have been shown to be feasible and beneficial for athletes to decrease their risk of sustaining a sport-related concussion, though the optimal duration, intensity, and frequency has yet to be determined.

Use of a factor analysis to assess biomechanical factors of American Sign Language in native and non-native signers.

Prior studies suggest that native (born to at least one deaf or signing parent) and non-native signers have different musculoskeletal health outcomes from signing, but the individual and combined biomechanical factors driving these differences are not fully understood. Such group differences in signing may be explained by the five biomechanical factors of American Sign Language that have been previously identified: ballistic signing, hand and wrist deviations, work envelope, muscle tension, and "micro" rests. Prior work used motion capture and surface electromyography to collect joint kinematics and muscle activations, respectively, from ten native and thirteen non-native signers as they signed for 7.5 min. Each factor was individually compared between groups. A factor analysis was used to determine the relative contributions of each biomechanical factor between signing groups. No significant differences were found between groups for ballistic signing, hand and wrist deviations, work envelope volume, excursions from recommended work envelope, muscle tension, or "micro" rests. Factor analysis revealed that "micro" rests had the strongest contribution for both groups, while hand and wrist deviations had the weakest contribution. Muscle tension and work envelope had stronger contributions for native compared to non-native signers, while ballistic signing had a stronger contribution for non-native compared to native signers. Using a factor analysis enabled discernment of relative contributions of biomechanical variables across native and non-native signers that could not be detected through isolated analysis of individual measures. Differences in the contributions of these factors may help explain the differences in signing across native and non-native signers.

Upper extremity muscle volumes and functional strength after resistance training in older adults.

Aging leads to a decline in strength and an associated loss of independence. The authors examined changes in muscle volume, maximum isometric joint moment, functional strength, and 1-repetition maximum (1RM) after resistance training (RT) in the upper extremity of older adults. They evaluated isometric joint moment and muscle volume as predictors of functional strength. Sixteen healthy older adults (average age 75 ± 4.3 yr) were randomized to a 6-wk upper extremity RT program or control group. The RT group increased 1RM significantly (p < .01 for all exercises). Compared with controls, randomization to RT led to greater functional pulling strength (p = .003), isometric shoulder-adduction moment (p = .041), elbow-flexor volume (p = .017), and shoulder-adductor volume (p = .009). Shoulder-muscle volumes and isometric moments were good predictors of functional strength. The authors conclude that shoulder strength is an important factor for performing functional reaching and pulling tasks and a key target for upper extremity RT interventions.

Development of a more biofidelic musculoskeletal model with humeral head translation and glenohumeral ligaments.

Computational musculoskeletal modeling is useful for understanding upper extremity biomechanics, especially when in vivo tests are unfeasible. A musculoskeletal model of the upper limb with increased biofidelity was developed by including humeral head translation (HHT) and ligaments. The model was validated and ligament contribution and effect of shoulder (thoracohumeral) elevation on HHT was evaluated. Humerus translated superiorly with increased elevation, with translations closely matching (avg. difference 2.83 mm) previous in vitro studies. HHT and ligament inclusion in the model will improve biomechanical predictions of upper extremity movements and study of conditions, like subacromial impingement, rotator cuff tear, or shoulder instability.

Treatment and Management of Work-Related Mild Traumatic Brain Injury in Physical Medicine and Rehabilitation.

ABSTRACT: The purpose of this narrative review was to assess work-related mild traumatic brain injury treatment approaches and outcomes. Literature indicates that incidence of work-related mild traumatic brain injury is high. Ability to return to work after injury is variable, with differences identified across industry sector, mechanisms of injury, sex, and timely treatment and referral. Additional challenges exist in the context of secondary gains (e.g., financial) and the potential for symptom exaggeration. Emerging evidence from studies outside the United States demonstrate the benefits of proactive assessment and treatment at the time of injury. These benefits can be further augmented by early referral to multidisciplinary treatment teams led by physical medicine and rehabilitation physicians. Opportunities for ongoing research and development of strategies to improve treatment, management, and more timely return to work for patients with occupational mild traumatic brain injury are discussed. It is concluded that challenges persist in treatment and management of patients with work-related mild traumatic brain injury as they present unique challenges not seen in those with nonwork-related mild traumatic brain injuries. The unique position of physical medicine and rehabilitation and the skills of physiatrists render them poised to lead multidisciplinary treatment teams for these patients and contribute to the development of a new guideline for return to work, with an emphasis on functional recovery.

Muscle compensation strategies to maintain glenohumeral joint stability with increased rotator cuff tear severity: A simulation study.

Rotator cuff tear (RCT) in older adults may cause decreased muscle forces and disrupt the force balance at the glenohumeral joint, compromising joint stability. Our objective was to identify how increased RCT severity affects glenohumeral joint loading and muscle activation patterns using a computational model. Muscle volume measurements were used to scale a nominal upper limb model's peak isometric muscle forces to represent force-generating characteristics of an average older adult male. Increased RCT severity was represented by systematically decreasing peak isometric muscle forces of supraspinatus, infraspinatus, and subscapularis. Five static postures in both scapular and frontal planes were evaluated. Results revealed that in both scapular and frontal planes, the peak glenohumeral joint contact force magnitude remained relatively consistent across increased RCT severity (average 1.5% and -4.2% change, respectively), and a relative balance of the transverse force couple is maintained even in massive RCT models. Predicted muscle activations of intact muscles, like teres minor, increased (average 5-30% and 4-17% in scapular and frontal planes, respectively) with greater RCT severity. This suggests that the system is prioritizing glenohumeral joint stability, even with severe RCT, and that unaffected muscles play a compensatory role to help stabilize the joint.

Trends and advancements in shoulder biomechanics research.

The 12th International Shoulder Group (ISG) Conference was held at Mayo Clinic in Rochester, Minnesota, USA, from August 12-13, 2018, and was hosted by Dr. Melissa (Missy) Morrow of Mayo Clinic and Dr. Meghan Vidt of Pennsylvania State University. This conference was held as a satellite conference to the annual 2018 American Society of Biomechanics Conference. This Editorial accompanies the Special Issue of the Journal of Electromyography and Kinesiology, and contains a selection of the work presented during the 12th Meeting of the ISG. Fourteen full-length articles describe advancements in shoulder research relevant to both basic science and clinical outlets. The work presented herein spans the research areas of methodology, mechanistic understanding, and clinical management. These areas are synergistic and equally important to propel the field forward and enhance impact. These manuscripts reinforce the dedication of the ISG and its members and showcase the ongoing drive toward translational application of these concepts across the common themes of rotator cuff, muscle, wheelchair & ergonomics, and methods & modeling. Highlights of each of the special issue publications are described within the context of the current trends in shoulder research and areas for further advancement.

Therapeutic Ultrasound and Shockwave Therapy for Tendinopathy: A Narrative Review.

ABSTRACT: Tendon injury is prevalent and costly in the United States, comprising 45% of the 66 million musculoskeletal injuries and costing $114 billion annually. Surgical and therapeutic methods, such as arthroscopic surgery, dry needling, and physical therapy, produce mixed success in reintroducing a healing response in tendinopathy due in part to inconsistent dosing and monitoring. Ultrasound is one therapeutic modality that has been shown to noninvasively induce bioeffects in tendon that may help promote healing. However, results from this modality have also been mixed. This review compares the current state of the field in therapeutic ultrasound and shockwave therapy, including low-intensity therapeutic ultrasound, extracorporeal shockwave therapy, and radial shockwave therapy, and evaluates the efficacy in treating tendinopathies with ultrasound. We found that the mixed successes may be attributed to the wide variety of achievable parameters within each broader treatment type and the lack of standardization in measurements and reporting. Despite mixed outcomes, all three therapies show potential as an alternative therapy with lower-risk adverse effects than more invasive methods like surgery. There is currently insufficient evidence to conclude which ultrasound modality or settings are most effective. More research is needed to understand the healing effects of these different therapeutic ultrasound and shockwave modalities.

Automated Tissue Strain Calculations Using Harris Corner Detection.

The elastic modulus, or slope of the stress-strain curve, is an important metric for evaluating tissue functionality, particularly for load-bearing tissues such as tendon. The applied force can be tracked directly from a mechanical testing system and converted to stress using the tissue cross-sectional area; however, strain can only be calculated in post-processing by tracking tissue displacement from video collected during mechanical testing. Manual tracking of Verhoeff stain lines pre-marked on the tissue is time-consuming and highly dependent upon the user. This paper details the development and testing of an automated processing method for strain calculations using Harris corner detection. The automated and manual methods were compared in a dataset consisting of 97 rat tendons (48 Achilles tendons, 49 supraspinatus tendons), divided into ten subgroups for evaluating the effects of different therapies on tendon mechanical properties. The comparison showed that average percent differences between the approaches were 0.89% and -2.10% for Achilles and supraspinatus tendons, respectively. The automated approach reduced processing time by 83% and produced similar results to the manual method when comparing the different subgroups. This automated approach to track tissue displacements and calculate elastic modulus improves post-processing time while simultaneously minimizing user dependency.

Effects of focused ultrasound and dry needling on tendon mechanical properties.

Tendon injuries are extremely common, resulting in mechanically weaker tendons that could lead to tendon rupture. Dry needling (DN) is widely used to manage pain and function after injury. However, DN is invasive and high inter-practitioner variability has led to mixed success rates. Focused ultrasound (fUS) is a non-invasive medical technology that directs ultrasound energy into a well-defined focal volume. fUS can induce thermal ablation or mechanical fractionation, with bioeffect type controlled through ultrasound parameters. Tendons must withstand high physiological loads, thus treatments maintaining tendon mechanical properties while promoting healing are needed. Our objective was to evaluate mechanical effects of DN and 3 fUS parameter sets, chosen to prioritize mechanical fractionation, on Achilles and supraspinatus tendons. Ex vivo rat Achilles and supraspinatus tendons (50 each) were divided into sham, DN, fUS-1, fUS-2, and fUS-3 (n = 10/group). Following treatment, tendons were mechanically tested. Elastic modulus of supraspinatus tendons treated with DN (126.64 ± 28.1 MPa) was lower than sham (153.02 ± 29.3 MPa; p = 0.0280). Stiffness and percent relaxation of tendons treated with DN (Achilles: 114.40 ± 31.6 N/mm; 49.10 ± 6.1%; supraspinatus: 109.53 ± 30.8 N/mm; 50.17 ± 7.6%) were lower (all p < 0.0334) than sham (Achilles: 141.34 ± 20.9 N/mm; 60.30 ± 7.7%; supraspinatus: 135.14 ± 30.2 N/mm; 60.85 ± 15.4%). Modulus of Achilles and supraspinatus tendons treated with fUS-1 (159.88 ± 25.7 MPa; 150.12 ± 22.0 MPa, respectively) were similar to sham (156.35 ± 23.0 MPa; 153.02 ± 29.3 MPa, respectively). These results suggest that fUS preserves mechanical properties better than DN, with fUS-1 performing better than fUS-2 and fUS-3. fUS should be studied further to fully understand its mechanical and healing effects to help evaluate fUS as an alternative, non-invasive treatment for tendon injuries.

Movement compensation is driven by the deltoid and teres minor muscles following severe rotator cuff tear.

BACKGROUND: Rotator cuff tears are common in older adults, negatively affecting function. Previous simulation-based studies reported more posterior and superior oriented glenohumeral loading with increased cuff tear severity and task performance, although corresponding muscle compensation strategies are unclear. Our objective is to determine how shoulder muscle forces change with increased rotator cuff tear severity during functional task performance. METHODS: Eight musculoskeletal models of increasing tear severity were developed to represent no rotator cuff tear to massive three-tendon tears. Simulations were performed using each combination of model and kinematics for five functional tasks. Individual muscle forces were averaged for each task and tear severity, then normalized by the sum of the muscle forces across the shoulder. Forces were compared across tear severity and muscle. FINDINGS: For muscle force contribution, interactions between tear severity and muscle and a main effect of muscle were seen for all tasks (P < 0.0001). Middle deltoid increased force contribution by >10% in the greatest tear severity model compared to no cuff tear model for all tasks (all P < 0.0001). Teres minor contribution increased by 7.7%, 5.6%, and 11% in the greatest tear severity model compared to the no cuff tear model for forward reach, axilla wash, and upward reach 105° tasks, respectively (all P < 0.0001). INTERPRETATION: Functional tasks elicit compensatory responses from uninjured muscles following severe cuff tears, notably in middle deltoid and teres minor, leading to posterior-superior glenohumeral loading. The muscles are potential targets for strengthening to avoid injury from sustained increased muscle force.

Upper extremity biomechanics in native and non-native signers.

BACKGROUND: Individuals fluent in sign language (signers) born to non-signing, non-deaf parents (non-natives) may have a greater injury risk than signers born to signing, deaf parents (natives). A comprehensive analysis of movement while signing in natives and non-natives has not been completed and could provide insight into the greater injury prevalence of non-natives. OBJECTIVE: The objective of this study was to determine differences in upper extremity biomechanics between non-natives and natives. METHODS: Strength, 'micro' rests, muscle activation, ballistic signing, joint angle, and work envelope were captured across groups. RESULTS: Non-natives had fewer rests (p = 0.002) and greater activation (p = 0.008) in non-dominant upper trapezius. For ballistic signing, natives had greater anterior-posterior jerk (p = 0.033) and for joint angle, natives demonstrated greater wrist flexion-extension range of motion (p = 0.040). Natives also demonstrated greater maximum medial-lateral (p = 0.015), and greater minimum medial-lateral (p = 0.019) and superior-inferior (p = 0.027) positions. CONCLUSIONS: We observed that natives presented with more rests and less activation, but greater ballistic tendencies, joint angle, and envelope compared to non-natives. Additional work should explore potential links between these outcomes and injury risk in signers.