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Objective: We examined interactions of overhead work location and direction of force application on shoulder muscular activity. Background: Overhead work tasks are common occupational stressors. Previous research has quantified influences of overhead work spatial placement and different force application directions but typically separately or exclusively for tasks done in the median plane. Method: Twenty female participants exerted 40 N of force in six directions (forward/backward, upward/downward, left/right) 150 cm off the floor while seated. An asymmetric pattern of 14 work locations spaced 15 cm centered directly overhead were evaluated. Results: Force direction and work location strongly influenced mean muscle activity ( F = 559, p < .01). Interaction effects existed between force direction and hand location in the transverse plane ( F = 21, p < .01), with increases as high as 49% in normalized mean muscle activity. Conclusion: Backward exertions produced the highest mean overall muscle activity across hand force directions, exceeding 30% maximum voluntary isometric exertion (MVE) across work locations, with higher activation of anterior deltoid, biceps, infraspinatus, supraspinatus, and upper and lower trapezius. Downward exertions had the lowest mean overall activity, with <10% MVE across work locations. Altered (up to 47%) muscular activity occurred as exertions moved laterally from the origin, and increasingly forward hand positions generally yielded decreased mean overall activity for most force directions. Application: This study provides previously unavailable submaximal shoulder muscular activity data for a wide range of overhead tasks. As such, it enables novel work design considerations that include modifying existing overhead elements to reduce or redistribute associated muscular demands.

Objective The aim was to review the biomechanical origins of occupational shoulder damage, while considering the complexity of shoulder mechanics and musculoskeletal consequences of diverse task demands. Background Accessible measures of physical exposures are the primary focus of occupational shoulder assessments and analyses. This approach has led to guidelines and intervention strategies that are often inadequate for mitigating shoulder disorders amongst the complexity of modern workplace demands. Integration of complex shoulder mechanics into occupational assessments, analyses, and interventions is critical for reducing occupational shoulder injury risk. Method This narrative review describes shoulder biomechanics in the context of common injury mechanisms and consequent injuries, with a particular focus on subacromial impingement syndrome. Several modulators of shoulder injury risk are reviewed, including fatigue, overhead work, office ergonomics considerations, and pushing and pulling task configurations. Results Relationships between work requirements, muscular demands, fatigue, and biomechanical tissue loads exist. This review highlights that consideration of specific workplace factors should be integrated with our knowledge of the intricate arrangement and interpersonal variability of the shoulder complex to proactively evaluate occupational shoulder demands and exposures. Conclusion A standard method for evaluating shoulder muscle exposures during workplace tasks does not exist. An integrated approach is critical for improved work design and prevention of shoulder tissue damage and accompanying disability. Application This review is particularly relevant for researchers and practitioners, providing guidance for work design and evaluation for shoulder injury prevention by understanding the importance of the unique and complex mechanics of the shoulder.

When Haynes and Larsen gathered self-report and official data from burglars, they found the high cost of recidivistic crime causes probation to cost more than prison. Gray and Olson analyzed the data again, arguing that researchers should measure rehabilitation, the difference between priors and recidivism, rather than recidivism alone. They found that prison may generate so much dehabilitation that it costs more than probation. In this study, the four authors analyze their conflicting results and show how cost-benefit analysis can inform policymakers.