The Effects of a Concurrent Task on Walking Over Firm and Foam Surfaces in Persons with Transfemoral Amputation
Morgan, Sara Janelle
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People with lower limb loss (LLL) experience profound mobility challenges, including a high incidence of falls, low balance confidence, and diminished walking activity. In addition to these mobility restrictions, many people with LLL report the need to concentrate on every step. This need to concentrate on walking may reflect increased reliance on cognitive control to compensate for loss of peripheral afferent feedback and efferent control. Reliance on cognitive control can be inferred using dual-task paradigms, where walking is performed with and without a concurrent task. This aims of this dissertation were to (1) review dual-task stance and walking research in persons with LLL, (2) quantify changes in walking associated with addition of a concurrent task in persons with transfemoral amputation (TFA) using microprocessor knees compared to controls without limb loss, and (3) use a dual-task paradigm to infer the need for cognitive control to walk over simple and challenging surfaces in participants with TFA using microprocessor knees and controls. Quantitative motion analysis was used to assess walking performance while walking with and without a concurrent cognitive task. People with TFA walked more slowly, with wider steps, and with reduced gait quality compared to controls across all task and surface conditions. However, people with TFA were not differentially affected by addition of a concurrent task in either surface condition. These results may suggest that participants with TFA adopt conservative walking patterns to reduce reliance on cognitive control for mobility. Future work will assess whole body movements and biomechanical measures of postural stability using estimated center of mass (COM) position. Link-segment models based on markers and participant mass distributions are used to estimate whole-body COM position. However, modeling guidelines are not established for people with LLL who use prostheses. Thus, the following aim was also examined: (4) assess the equivalency of two modeling approaches used to estimate COM position- an anatomical approach, based on the mass distribution properties of the intact side; and a prosthetic-specific approach, based on prosthetic component masses. The anatomical and prosthetic-specific models from two participants with TFA produced small, but potentially meaningful differences in calculated COM parameters.