The University of Massachusetts Amherst
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Sarah Roelker

Assistant Professor

Academic Background

2017-2020, Post-Doctoral Research Fellow - The University of Texas at Austin, Mechanical Engineering, Austin, TX

2015-2017, PhD - The Ohio State University, Mechanical Engineering, Columbus, Ohio

2012-2015, M.S. - The Ohio State University, Mechanical Engineering, Columbus, Ohio

2008-2012, B.S. - The Ohio State University, Biomedical Engineering, Columbus, Ohio

Current Research 

I am currently studying the mechanisms underlying impaired balance control during walking in individuals with post-stroke hemiparesis in collaboration with Dr. Richard Neptune at the University of Texas Austin. In particular, I am investigating the relationship between specific deficits in the flexibility of their motor control system and muscle contributions to foot placement and ground reaction forces (GRFs) during walking. Together, the foot placement and GRFs determine the momentum of the body segments about an individual's center of mass. The ability to maintain this momentum within a small range is associated with improved dynamic balance control. By identifying the relative importance of these two variables (foot placement and GRFs) to maintaining balance control and determining the motor control and muscle-level contributions to the increased range of momentum observed in patients post-stroke with specific motor control deficits, we can identify patient-specifc gait rehabilitation targets to improve dynamic balance and reduce fall-risk post-stroke. I am also currently studying differences in muscle function and motor control between running and skipping gaits in collaboration with Drs. Paul Devita and John Willson at East Carolina University and Dr. Richard Neptune at UT-Austin. Skipping is typically the last locomotor skill that children develop and is considered to require the most coordination of typical locomotor tasks. In addition, skipping has recently been suggested to have decreased knee contact forces yet increased metabolic cost compared to running. Thus, skipping may be an ideal transition gait between walking and running for individuals recovering from a knee injury looking to return to sport or an alternative aerobic exercise to reduce knee joint loading in older adults. I am currently using musculoskeletal modeling and simulation techniques to identify differences in joint loading at the ankle and hip in addition to the knee between running and skipping to determine if skipping requires universally reduced joint loading across all lower extremity joints and the changes in muscle function and joint mechanics that contribute to that reduced joint loading despite greater metabolic cost. Furthermore, I am investigating differences in neuromuscular control between running and skipping to identify how the nervous system adapts to coordinate more challenging gaits.

Research Interests 

My research leverages musculoskeletal modeling and simulation techniques to gain insights into the neuromusculoskeletal mechanisms underlying typical and impaired locomotion. The overall goal of this work is to identify physical therapy intervention and rehabilitation targets to improve locomotor function and quality of life in individuals with impaired mobility. A primary aim of my research is to identify the biomechanic and neuromuscular mechanisms contributing to impaired dynamic balance in populations with increased fall-risk. In addition, I am interested in characterizing motor control across locomotor tasks of varying levels of difficulty (e.g., walking, stair climbing, running, skipping) and in the presence of increased cognitive load (e.g., walking and talking) to determine how the nervous system alters motor control to adjust to varying task demands and how this control is impaired in the presence of neurological changes due to aging or disease. Ultimately this work will inform more robust models of neuromuscular control that can be incorporated into current musculoskeletal models to improve their ability to predict an individual's locomotor function in response to rehabilitation treatments and thus develop patient-specific treatment plans.

Roelker SA, Kautz SA, Neptune RR. Muscle Contributions to Mediolateral and Anteroposterior Foot Placement During Walking. J Biomech. 95:109310, 2019
Roelker SA, Bowden MG, Kautz SA, Neptune RR. Paretic propulsion as a measure of walking performance and functional motor recovery post-stroke: a review. Gait Posture. 68:6-14 2019.
Schloemer SA, Thompson JA, Siler A, Thelen DG, Siston, RA. Age-Related Differences in Gait Kinematics, Kinetics, and Muscle Function: A Principal Component Analysis. Ann Biomed Eng. 45(3): 695-710, 2017.
Schloemer SA, Cotter JA, Jamison ST, Chaudhari AMW. Time to Contact Measures Demonstrate Modulation of Postural Control during a Dynamic Lower Extremity Task. Gait Posture. 38:658-62, 2013.
Contact Info

Totman 159B
30 Eastman Lane
Amherst, MA 01003-9292

Office: (413) 577-6455