TY - JOUR
T1 - Ankle Exoskeleton Assistance Can Improve Over-Ground Walking Economy in Individuals with Cerebral Palsy
AU - Orekhov, Greg
AU - Fang, Ying
AU - Luque, Jason
AU - Lerner, Zachary F.
N1 - Funding Information:
Manuscript received September 13, 2019; revised November 22, 2019 and December 28, 2019; accepted January 3, 2020. Date of publication January 8, 2020; date of current version February 12, 2020. This work was supported in part by the NSF under Grant 1756029 and in part by the NIH under Grant 1R15HD099664. (Corresponding author: Zachary F. Lerner.) Greg Orekhov, Ying Fang, and Jason Luque are with the Mechanical Engineering Department, Northern Arizona University, Flagstaff, AZ 86011 USA.
Publisher Copyright:
© 2001-2011 IEEE.
PY - 2020/2
Y1 - 2020/2
N2 - Individuals with neuromuscular impairment from conditions like cerebral palsy face reduced quality of life due to diminishing mobility and independence. Lower-limb exoskeletons have potential to aid mobility, yet few studies have investigated their use during over-ground walking - an exercise that may contribute to our understanding of potential benefit in free-living settings. The goal of this study was to determine the potential for adaptive plantar-flexor assistance from an untethered ankle exoskeleton to improve over-ground walking economy and speed. Six individuals with cerebral palsy completed three consecutive daily over-ground training sessions to acclimate to, and tune, assistance. During a final assessment visit, metabolic cost, walking speed, and soleus electromyography were collected for baseline, unpowered, low, training-tuned, and high assistance conditions. Compared to each participant's baseline condition, we observed a 3.9 ± 1.9% (p = 0.050) increase in walking speed and a 22.0 ± 4.5% (p = 0.002) reduction in soleus activity with training-tuned assistance; metabolic cost of transport was unchanged (p = 0.130). High assistance resulted in an 8.5 ± 4.0% (p = 0.042) reduction in metabolic cost of transport, a 6.3 ± 2.6% (p = 0.029) increase in walking speed, and a 25.0 ± 4.0% (p < 0.001) reduction in soleus activity. Improvement in exoskeleton-assisted walking economy was related to pre-training baseline walking speed ( $\text{R}^{{2}}={0.94}$ , p = 0.001); the slower and more impaired participants improved the most. Energy cost and preferred walking speed remained generally unchanged for the faster and less impaired participants. These findings demonstrate that powered ankle exoskeletons have the potential to improve mobility-related outcomes for some people with cerebral palsy.
AB - Individuals with neuromuscular impairment from conditions like cerebral palsy face reduced quality of life due to diminishing mobility and independence. Lower-limb exoskeletons have potential to aid mobility, yet few studies have investigated their use during over-ground walking - an exercise that may contribute to our understanding of potential benefit in free-living settings. The goal of this study was to determine the potential for adaptive plantar-flexor assistance from an untethered ankle exoskeleton to improve over-ground walking economy and speed. Six individuals with cerebral palsy completed three consecutive daily over-ground training sessions to acclimate to, and tune, assistance. During a final assessment visit, metabolic cost, walking speed, and soleus electromyography were collected for baseline, unpowered, low, training-tuned, and high assistance conditions. Compared to each participant's baseline condition, we observed a 3.9 ± 1.9% (p = 0.050) increase in walking speed and a 22.0 ± 4.5% (p = 0.002) reduction in soleus activity with training-tuned assistance; metabolic cost of transport was unchanged (p = 0.130). High assistance resulted in an 8.5 ± 4.0% (p = 0.042) reduction in metabolic cost of transport, a 6.3 ± 2.6% (p = 0.029) increase in walking speed, and a 25.0 ± 4.0% (p < 0.001) reduction in soleus activity. Improvement in exoskeleton-assisted walking economy was related to pre-training baseline walking speed ( $\text{R}^{{2}}={0.94}$ , p = 0.001); the slower and more impaired participants improved the most. Energy cost and preferred walking speed remained generally unchanged for the faster and less impaired participants. These findings demonstrate that powered ankle exoskeletons have the potential to improve mobility-related outcomes for some people with cerebral palsy.
KW - Adaptive control
KW - ankle assistance
KW - cerebral palsy
KW - exoskeleton
KW - metabolic cost of transport
KW - over-ground walking
KW - plantarflexion
KW - soleus muscle activity
KW - walking speed
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U2 - 10.1109/TNSRE.2020.2965029
DO - 10.1109/TNSRE.2020.2965029
M3 - Article
C2 - 31940542
AN - SCOPUS:85078040198
SN - 1534-4320
VL - 28
SP - 461
EP - 467
JO - IEEE Transactions on Neural Systems and Rehabilitation Engineering
JF - IEEE Transactions on Neural Systems and Rehabilitation Engineering
IS - 2
M1 - 8952603
ER -