Article

While level walking with a pneumatic ankle-foot exoskeleton is studied
extensively, less is known on uphill walking.
The goals of this study were to get
a better understanding of the biomechanical adaptations and the influence of
actuation timing on metabolic cost during uphill walking with a plantarflexion
assisting exoskeleton. Seven female subjects walked on a treadmill with 15%
inclination at 1.36 ms(-1) in five conditions (4 min): one condition with an
unpowered exoskeleton and four with a powered exoskeleton with onset of pneumatic
muscle actuation at 19, 26, 34 and 41% of stride. During uphill walking the
metabolic cost was more than 10% lower for all powered conditions compared to the
unpowered condition. When actuation onset was in between 26 and 34% of the
stride, metabolic cost was suggested to be minimal. While it was expected that
exoskeleton assistance would reduce muscular activity of the plantarflexors
during push-off, subjects used the additional power to raise the body centre of
mass in the beginning of each step to a higher point compared to unpowered
walking. This reduced the muscular activity in the m. vastus lateralis and the m.
biceps femoris as less effort was necessary to reach the highest body centre of
mass position in the single support phase. In conclusion, subjects can use
plantarflexion assistance during the push-off to reduce muscular activity in more
proximal joints in order to minimize energy cost during uphill locomotion.
Kinetic data seem necessary to fully understand this mechanism, which highlights
the complexity of human-exoskeleton interaction.
CI - Copyright (c) 2014 Elsevier B.V. All rights reserved.

Langue : ANGLAIS