Simulated Development of Assistive Devices to Aid Older Adults in Ascending Stairs
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Date
2018-05
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The Ohio State University
Abstract
Stair climbing is an important part of daily life. However, for older adults, stair climbing is one of the top five most difficult tasks, and the inability to climb stairs leads to a decreased quality of life. Assistive devices provide a way for people who cannot climb stairs to regain their mobility and improve their lives. While there are several assistive devices for climbing stairs on the market, assistive devices that use inexpensive elements like springs and assist joints like the knee and ankle have not been investigated. Simulations allow us to understand how assistive devices affect muscles during stair climbing and to test several variations of assistive devices before creating physical prototypes. In this study, I used OpenSim, software that models the human musculoskeletal system, to add ideal, massless torsional springs to simulations of individuals ascending stairs. Four healthy participants (4 female, age = 65.00 ± 4.76 years, height = 1.61 ± 0.02 m, weight = 58.59 ± 6.11 kg) provided IRB-approved written consent. Motion capture and electromyography data were previously collected and used to create individual models in OpenSim. Static Optimization (SO) was used to resolve the kinematics of the individuals into forces and activations. Metabolic cost was estimated from the SO activations and compared to an individual with no assistance. In addition, maximum forces produced by certain muscles while ascending stairs were compared with and without varying assistive devices. Overall metabolic cost increased for all spring stifffnesses and locations. The simulation of the unassisted individuals was the least metabolically expensive on average. However, two individuals had a decrease in overall metabolic cost when assisted at the ankle with a k =1 Nm/deg spring at the ankle, and one individual saw a decrease in metabolic cost when a k = 1 Nm/ deg spring was located at the hip. The vastus lateralis, vastus intermedius, vastus medialis, gluteus maximus, and soleus decreased in metabolic cost for all spring stiffnesses and for all joints. Overall, a spring with stiffness k = 1 Nm/deg located at the ankle was the least metabolically expensive spring simulated in this study, increasing the cost by 3 ± 11%. A spring with stiffness k = 5 Nm/deg located at the knee was the most metabolically expensive device, increasing overall cost by 1421 ± 421%. The results of this study can be used to further develop assistive devices to help older adults climb stairs and ultimately improve their quality of life.
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Keywords
Assistive devices, Biomechanics, Stair climbing, Older adults