What’s Your Potential? The Influence of Joint Kinematics on a Muscle’s Ability to Contribute to the Sit-to-Stand Transfer
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Date
2017-03
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Abstract
Induced Acceleration Analysis (IAA) estimates how muscles facilitate movement by supporting the center of mass (COM) against the force of gravity and contributing to the progression of the COM in the direction of movement. Prior IAA studies provide a baseline of how muscles facilitate activities of daily living; however, the underlying elements of IAA describing the mechanisms by which muscle forces contribute to movement are complex and not fully understood. While muscle force greatly impacts IAA, kinematics influence these forces, as well as muscle moment arms and contributions to movement. This kinematic component of IAA is important, as it has been suggested that for patients to utilize strength gains from rehabilitation, kinematic retraining may be necessary to reprogram the motor pattern. However, existing methods for estimating muscle contributions to movement require extensive time and experimental resources, making patient specific-IAA impractical in a clinical setting. Therefore, the purpose of this study is to develop an efficient method for determining how changes to lower extremity joint kinematics affect the potential of individual muscles to contribute to support during the sit-to-stand (STS) transfer. A 4 link 2-dimensional sagittal plane model with 4 rotational joints was used to assess the effect of changes to kinematics on the function of 23 lower extremity muscles during each task. Kinematics were varied at each joint throughout ranges that are commonly observed during the momentum transfer phase of the STS. For each kinematic position, a muscle’s potential to contribute to support was estimated. Our new method predicted that positioning the feet more posteriorly (under the COM) during the STS increases the potential of the gluteus maximus, biceps femoris long head, vasti, and gastrocnemius to contribute to support. Additionally, a more anteriorly tilted pelvis increased the potential of the quadriceps muscles, but decreased the potential of posterior muscles. These results were verified by muscle potentials calculated using traditional experimental and simulation methods. This research represents the first effort to systematically evaluate how changes in joint kinematics affect muscle contributions to acceleration. The methods presented in this study demonstrate a mechanism for determining the cause of abnormal movement and for identifying potential rehabilitation techniques that leverage both kinematics and muscle strength to improve mobility.
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Engineering: 3rd Place (The Ohio State University Edward F. Hayes Graduate Research Forum)
Keywords
induced accelerations, musculoskeletal model, muscle function, kinematics