http://www.jneuroengrehab.com/content/12/1/23/abstract
Journal of NeuroEngineering and Rehabilitation 2015, 12:23
doi:10.1186/s12984-015-0015-7
Published: 25 February 2015
Published: 25 February 2015
Abstract
Background
In persons post-stroke, diminished ankle joint function can contribute to inadequate
gait propulsion. To target paretic ankle impairments, we developed a neuromechanics-based
powered ankle exoskeleton. Specifically, this exoskeleton supplies plantarflexion
assistance that is proportional to the user’s paretic soleus electromyography (EMG)
amplitude only during a phase of gait when the stance limb is subjected to an anteriorly
directed ground reaction force (GRF). The purpose of this feasibility study was to
examine the short-term effects of the powered ankle exoskeleton on the mechanics and
energetics of gait.
Methods
Five subjects with stroke walked with a powered ankle exoskeleton on the paretic limb
for three 5 minute sessions. We analyzed the peak paretic ankle plantarflexion moment,
paretic ankle positive work, symmetry of GRF propulsion impulse, and net metabolic
power.
Results
The exoskeleton increased the paretic plantarflexion moment by 16% during the powered
walking trials relative to unassisted walking condition (p < .05). Despite this enhanced
paretic ankle moment, there was no significant increase in paretic ankle positive
work, or changes in any other mechanical variables with the powered assistance. The
exoskeleton assistance appeared to reduce the net metabolic power gradually with each
5 minute repetition, though no statistical significance was found. In three of the
subjects, the paretic soleus activation during the propulsion phase of stance was
reduced during the powered assistance compared to unassisted walking (35% reduction
in the integrated EMG amplitude during the third powered session).
Conclusions
This feasibility study demonstrated that the exoskeleton can enhance paretic ankle
moment. Future studies with greater sample size and prolonged sessions are warranted
to evaluate the effects of the powered ankle exoskeleton on overall gait outcomes
in persons post-stroke.
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