PROJECT SUMMARY
Clinicians rely on examination of movement to inform treatment planning for shoulder dysfunction. However, the
links between scapular movement abnormalities, muscle activation, and rotator cuff deformation remain unclear,
limiting the development of precise, individualized treatment of each patient. The long-term goal of this research
is to understand movement-related development and treatment of shoulder dysfunction. The overall objectives
for this project are to identify muscle activation and rotator cuff compression or glenoid obstruction, as proxies
for deformation, in two specific scapular movement groups. The hypotheses are that individuals who
demonstrate an excessive scapular anterior tilt movement pattern will have relatively reduced serratus anterior
muscle activity and relatively increased rotator cuff compression from the coracoacromial (CA) arch. Individuals
who demonstrate a scapular lateralization movement pattern will have relatively reduced lower trapezius muscle
activity and relatively increased rotator cuff obstruction from the glenoid. The hypotheses will be tested through
two specific aims. 1: Determine the extent to which scapulothoracic muscle activation differs during arm
elevation between two specific scapular movement groups. The approach for this aim will be to classify
participants into the two movement patterns based on overhead reaching kinematics derived from biplane video
radiography and optical motion capture. Simultaneously collected electromyography will record muscle activity
of key scapulothoracic muscles which will be compared between groups. 2: Determine the extent to which
two specific scapular movement patterns during arm elevation result in subacromial compression or
glenoid obstruction of the rotator cuff. The approach for this aim will be to recreate each participant’s arm
motion using models of their humerus, scapula, and supraspinatus (rotator cuff) tendon and their specific arm
raising kinematics. In instances when the tendon and the CA arch or glenoid make contact, the volume of
intersection of the models will be quantified as a proxy for tendon deformation. This proposed research will
contribute to science through the elucidation of patterns of muscle activation and rotator cuff tendon deformation
in individuals with two specific scapular movement patterns. These contributions are expected to be significant
because they will provide a framework for clinical treatment planning with regard to specific movement patterns
and muscle activity patterns that should be targeted for individualized treatment. This proposed study is part of
a fellowship training plan including medical imaging and advanced statistical analysis coursework, guided lab
training, and mentored training in research skills needed to become an independent biomechanical researcher.
Research activities and training will take place at the University of Minnesota. The University’s expansive
research infrastructure, the multi-disciplinary Program in Rehabilitation Science, and the Minnesota
Rehabilitation Biomechanics Laboratory create an ideal environment for completing this research and training.