The overall goal of this project is to develop modular, lower-limb, powered orthoses that fit to user-specific weakened joints and control force/torque in a manner that enhances voluntary motion in broad patient populations. This project aims to establish feasibility of assisting different populations with these modular powered orthoses. The investigators hypothesize that assisting lower-limb musculature with modular powered orthoses will improve 1) lifting/lowering posture in able-bodied subjects and 2) functional outcomes in elderly subjects.
The overall goal of this project is to develop modular, lower-limb, powered orthoses that fit to user-specific weakened joints and control force/torque in a manner that enhances voluntary motion in broad patient populations. Conventional orthoses tend to immobilize joints, and emerging powered orthoses constrain voluntary motion by using highly geared electric motors and/or control methods that force the user to follow a specific gait pattern. Consequently, these devices have not seen widespread success across populations with weakened voluntary control due to advanced age, musculoskeletal disorders, etc. These heterogeneous populations require partial, not full, assistance of user-specific muscle groups during daily activities. However, there is a fundamental gap in knowledge about how to design and control powered orthoses to assist the user without constraining their motion. The central hypothesis of this project is that high-torque, low-inertia motor systems controlled with energetic objectives will enable modular powered orthoses to partially assist the joints. High-torque electric motors combined with minimal transmissions can be freely rotated (i.e., backdriven) by human joints, allowing the use of an emerging torque control method called energy shaping to reduce the perceived weight/inertia of the body during any motion. By mounting these modular actuators to commercial orthoses, this technology will be easily prescribed/configured by clinicians. This project aims to establish feasibility of assisting different populations with modular powered orthoses. The investigators hypothesize that assisting lower-limb musculature with modular powered orthoses will improve 1) lifting/lowering posture in able-bodied subjects and 2) functional outcomes in elderly subjects.
Study Type
INTERVENTIONAL
Allocation
NA
Purpose
OTHER
Masking
NONE
Enrollment
33
This study will investigate modular, lower-limb, powered orthoses that fit to user-specific weakened joints and control force/torque in a manner that enhances voluntary motion in broad patient populations. The central hypothesis is that high-torque, low-inertia motor systems controlled with energetic objectives will enable modular powered orthoses to partially assist the joints. High-torque electric motors combined with minimal transmissions can be freely rotated (i.e., backdriven) by human joints, allowing the use of an emerging torque control method called energy shaping to reduce the perceived weight/inertia of the body during any motion. By mounting these modular actuators to commercial orthoses, this technology will be easily prescribed/configured by clinicians.
Rehab Lab, University of Michigan
Ann Arbor, Michigan, United States
RECRUITINGPowered orthosis effect (muscle effort)
For each orthosis module tested, electromyography (EMG) readings will be normalized per-muscle by the peak EMG observed during the no-orthosis condition, and then averaged over the cycle and across repetitions to obtain "normalized exertion" values. Performance will be assessed by the difference between the orthosis condition and no-orthosis condition, averaging across tasks and muscles measured for the joint module.
Time frame: 1 day
Time to complete 10 reps of lifting/lowering
Time to complete 10 reps of L\&L will be measured post-fatigue in healthy subjects.
Time frame: 1 day, assessed per experimental condition (i.e. with orthosis and without orthosis)
Gait speed
Gait speed will be determined by the time to complete a 10-meter walk test. This will be the primary outcome measure for elderly subjects.
Time frame: 1 day, assessed per experimental condition (i.e. with orthosis and without orthosis)
Powered orthosis effect (biological torque)
For each orthosis module tested, peak biological torque (estimated by inverse dynamics) will be averaged across repetitions. Performance will be assessed by the difference between the orthosis condition and no-orthosis condition, averaging across tasks.
Time frame: 1 day, assessed per experimental condition (i.e. with orthosis and without orthosis)
Minimum chair height for successful sit-to-stand
We will evaluate the minimum chair height from which elderly participants can successfully rise with and without the knee exoskeleton.
Time frame: 1 day, assessed per experimental condition (i.e. with orthosis and without orthosis)
Joint power
For elderly participants, we will evaluate the peak values of biological and total (exo+biological) joint power with and without the exoskeleton.
Time frame: 1 day, assessed per experimental condition (i.e. with orthosis and without orthosis)
User satisfaction
User satisfaction / perception of device effectiveness over an ambulation circuit (sit-to-stand, walk up and down a ramp, walk up and down a staircase) will be measured post-fatigue in healthy subjects using a modified Quebec User Evaluation of Satisfaction with Assistive Technology (QUEST 2.0) survey. The purpose of the scale is to evaluate user device satisfaction and consists of 12 items asking the user to rate their satisfaction on a scale of 1 to 5, where 1 = "not satisfied at all" and 5 = "very satisfied".
Time frame: 1 day, assessed per experimental condition (i.e. with orthosis and without orthosis)
Thorax angle
This is the global thorax angle (with respect to vertical) during a lifting/lowering cycle. This will be a secondary outcome measure for able-bodied subjects.
Time frame: 1 day, assessed per experimental condition (i.e. with orthosis and without orthosis)
Stair ascent gait style
Step-to-step vs. step-over-step gait style will be evaluated for the exo condition vs no exo condition for elderly participants.
Time frame: 1 day, assessed per experimental condition (i.e. with orthosis and without orthosis)
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