Presentation description

The energy required to complete activities of daily living can increase due to age, muscular disorders, and neurological conditions, potentially leading to fatigue, injury risk, and higher healthcare costs. Numerous assistive devices have been developed to address this increased energy demand, but the muscular mechanisms underlying their influence is yet to be fully elucidated. Musculoskeletal modeling and simulation provide an approach by which insights into these muscle-specific mechanisms can be examined. The aim of this study was to examine the effects of increased footwear stiffness via a low-cost assistive device on lower-limb muscle energy expenditure using computational musculoskeletal simulations. Previously captured experimental motion capture measurements during treadmill walking were used to inform these simulations. A torsional spring was added about the OpenSim 'gait2354' lower-extremity model's metatarsophalangeal joint to model the stiffening effect of the carbon fiber insoles. Footwear stiffness values for each condition (low, medium, and high stiffness) were obtained from 3-point bending tests. To conduct simulations, the model was anthropometrically scaled, then muscle actuator control values to produce dynamically consistent kinematic and kinetic data were generated using a residual reduction algorithm and computed muscle control. The power fluctuations and net work performed by the distal foot in vivo and simulated MTP joint showed similar trends during the stance phase. The stance phase averaged soleus fascicle shortening velocity decreased with increasing stiffness in both the experimental and simulated data. Additionally, the variation in experimental and simulated whole-body metabolic cost of transport matched well. In the simulation, muscles crossing the ankle joint consumed less energy with increasing footwear stiffness. This initial modelling framework has the potential to understand individual muscle contributions to whole-body metabolic cost, thereby improving future assistive devices aimed at reducing energy requirements.