Abstract
We used a lower limb robotic exoskeleton controlled by the wearer's muscle activity to study human locomotor adaptation to disrupted muscular coordination. Ten healthy subjects walked while wearing a pneumatically powered ankle exoskeleton on one limb that effectively increased plantar flexor strength of the soleus muscle. Soleus electromyography amplitude controlled plantar flexion assistance from the exoskeleton in real time. We hypothesized that subjects' gait kinematics would be initially distorted by the added exoskeleton power, but that subjects would reduce soleus muscle recruitment with practice to return to gait kinematics more similar to normal. We also examined the ability of subjects to recall their adapted motor pattern for exoskeleton walking by testing subjects on two separate sessions, 3 days apart. The mechanical power added by the exoskeleton greatly perturbed ankle joint movements at first, causing subjects to walk with significantly increased plantar flexion during stance. With practice, subjects reduced soleus recruitment by ∼35% and learned to use the exoskeleton to perform almost exclusively positive work about the ankle. Subjects demonstrated the ability to retain the adapted locomotor pattern between testing sessions as evidenced by similar muscle activity, kinematic and kinetic patterns between the end of the first test day and the beginning of the second. These results demonstrate that robotic exoskeletons controlled by muscle activity could be useful tools for testing neural mechanisms of human locomotor adaptation.
Original language | English (US) |
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Pages (from-to) | 2636-2644 |
Number of pages | 9 |
Journal | Journal of Biomechanics |
Volume | 40 |
Issue number | 12 |
DOIs | |
State | Published - 2007 |
Funding
The authors thank Catherine Kinnaird and members of the Human Neuromechanics Laboratory for assistance in collecting and analyzing data. We also thank Ammanath Peethambaran, C.O., and the staff of the University of Michigan Orthotics and Prosthetics Center for help with designing and fabricating parts of the exoskeleton. Supported by NIH R01 NS045486.
Keywords
- Biomechanics
- EMG
- Gait
- Locomotion
- Motor learning
- Powered orthosis
ASJC Scopus subject areas
- Biophysics
- Rehabilitation
- Biomedical Engineering
- Orthopedics and Sports Medicine