Lower limb joint biomechanics-based identification of gait transitions in between level walking and stair ambulation

Abstract

Lower limb exoskeletons and lower limb prostheses have the potential to reduce gait limitations during stair ambulation. To develop robotic assistance devices, the biomechanics of stair ambulation and the required transitions to level walking have to be understood. This study aimed to identify the timing of these transitions, to determine if transition phases exist and how long they last, and to investigate if there exists a joint-related order and timing for the start and end of the transitions. Therefore, this study analyzed the kinematics and kinetics of both transitions between level walking and stair ascent, and between level walking and stair descent (12 subjects, 25.4 yrs, 74.6 kg). We found that transitions primarily start within the stance phase and end within the swing phase. Transition phases exist for each limb, all joints (hip, knee, ankle), and types of transitions. They have a mean duration of half of one stride and they do not last longer than one stride. The duration of the transition phase for all joints of a single limb in aggregate is less than 35% of one stride in all but one case. The distal joints initialize stair ascent, while the proximal joints primarily initialize the stair descent transitions. In general, the distal joints complete the transitions first. We believe that energy- and balance-related processes are responsible for the joint-specific transition timing. Regarding the existence of a transition phase for all joints and transitions, we believe that lower limb exoskeleton or prosthetic control concepts should account for these transitions in order to improve the smoothness of the transition and to thus increase the user comfort, safety, and user experience. Our gait data and the identified transition timings can provide a reference for the design and the performance of stair ambulation- related control concepts.

Performance of Sonomyographic and Electromyographic Sensing for Continuous Estimation of Joint Torque During Ambulation on Multiple Terrains

“…Current lower-limb powered assistive devices rely on finite-state intrinsic controllers that are capable of mimicking natural locomotion during specific cyclic tasks (e.g., ramp or level ground ambulation) at relatively steadystate speeds [2], [5], [6]. Volitional control techniques could improve upon these capabilities by empowering users to complete a larger variety of known or unknown tasks, as well as perform transitions between tasks and speeds that often have distinct biomechanical signatures, increasing the users ability to adapt to real-world variability [7]- [9]. However, to fully capture the advanced capabilities of volitional control, there remains a need for an intuitive sensing interface to continuously and accurately estimate an appropriate joint-level biomechanical response.…”

Real-Time Adaptation of an Artificial Neural Network for Transfemoral Amputees Using a Powered Prosthesis

“…Error rates were expectedly higher in transitional steps, when compared to steady-state. Due to known additional complexities in the transition kinematics [ 29 ] and because far fewer transition steps were available for classification, transitional estimation errors were often a magnitude higher than steady-state, as seen in Table II . However, because transitional steps comprise only a sub-set of the entire dataset, their higher error rates have a minimal impact on the collective average error.…”

Exploring surface electromyography (EMG) as a feedback variable for the human-in-the-loop optimization of lower limb wearable robotics

“…Literature shows that transitions where the environment forces a transition, such as a transfer from level walking to stair ambulation, are realized within three strides (Grimmer et al, 2020 ). Three strides are also required to return to a steady gait after stumbling perturbations (Cordero et al, 2003 ).…”