Altering gait variability with an ankle exoskeleton

Prokopios Antonellis, Samuel Galle, Dirk De Clercq, Philippe Malcolm

Research output: Contribution to journalArticle

Abstract

Exoskeletons can influence human gait. A healthy gait is characterized by a certain amount of variability compared to a non-healthy gait that has more inherent variability; however which exoskeleton assistance parameters are necessary to avoid increasing gait variability or to potentially lower gait variability below that of unassisted walking are unknown. This study investigated the interaction effects of exoskeleton timing and power on gait variability. Ten healthy participants walked on a treadmill with bilateral ankle-foot exoskeletons under ten conditions with different timing (varied from 36% to 54% of the stride) and power (varied from 0.2 to 0.5 Wkg -1 ) combinations. We used the largest Lyapunov exponent (LyE) and maximum Floquet multiplier (FM) to evaluate the stride-to-stride fluctuations of the kinematic time series. We found the lowest LyE at the ankle and a significant reduction versus powered-off with exoskeleton power (summed for both legs) of 0.45 Wkg -1 and actuation timing at 48% of the stride cycle. at the knee, a significant positive effect of power and a negative interaction effect of power and timing were found for LyE. We found significant positive interaction effects of the square of timing and power for LyE at the knee and hip joints. In contrast, the FM at the ankle increased with increasing power and later timing. We found a significant negative effect of power and a positive interaction effect of power and timing for FM at the knee and no significant effects of any of the exoskeleton parameters for FM at the hip. The ability of the exoskeleton to reduce the LyE at the ankle joint offers new possibilities in terms of altering gait variability, which could have applications for using exoskeletons as rehabilitation devices. Further efforts could examine if it is possible to simultaneously reduce the LyE and FM at one or more lower limb joints.

Original languageEnglish (US)
Article numbere0205088
JournalPloS one
Volume13
Issue number10
DOIs
StatePublished - Oct 2018

Fingerprint

Exercise equipment
exoskeleton
gait
Gait
Ankle
Patient rehabilitation
Time series
Kinematics
multipliers
knees
joints (animal)
hips
Knee
Ankle Joint
Hip Joint
Knee Joint
Exoskeleton (Robotics)
Biomechanical Phenomena
exercise equipment
Walking

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)
  • Agricultural and Biological Sciences(all)

Cite this

Altering gait variability with an ankle exoskeleton. / Antonellis, Prokopios; Galle, Samuel; De Clercq, Dirk; Malcolm, Philippe.

In: PloS one, Vol. 13, No. 10, e0205088, 10.2018.

Research output: Contribution to journalArticle

Antonellis, Prokopios ; Galle, Samuel ; De Clercq, Dirk ; Malcolm, Philippe. / Altering gait variability with an ankle exoskeleton. In: PloS one. 2018 ; Vol. 13, No. 10.
@article{13e9d7d6882e4e94b837d32d40fc314d,
title = "Altering gait variability with an ankle exoskeleton",
abstract = "Exoskeletons can influence human gait. A healthy gait is characterized by a certain amount of variability compared to a non-healthy gait that has more inherent variability; however which exoskeleton assistance parameters are necessary to avoid increasing gait variability or to potentially lower gait variability below that of unassisted walking are unknown. This study investigated the interaction effects of exoskeleton timing and power on gait variability. Ten healthy participants walked on a treadmill with bilateral ankle-foot exoskeletons under ten conditions with different timing (varied from 36{\%} to 54{\%} of the stride) and power (varied from 0.2 to 0.5 Wkg -1 ) combinations. We used the largest Lyapunov exponent (LyE) and maximum Floquet multiplier (FM) to evaluate the stride-to-stride fluctuations of the kinematic time series. We found the lowest LyE at the ankle and a significant reduction versus powered-off with exoskeleton power (summed for both legs) of 0.45 Wkg -1 and actuation timing at 48{\%} of the stride cycle. at the knee, a significant positive effect of power and a negative interaction effect of power and timing were found for LyE. We found significant positive interaction effects of the square of timing and power for LyE at the knee and hip joints. In contrast, the FM at the ankle increased with increasing power and later timing. We found a significant negative effect of power and a positive interaction effect of power and timing for FM at the knee and no significant effects of any of the exoskeleton parameters for FM at the hip. The ability of the exoskeleton to reduce the LyE at the ankle joint offers new possibilities in terms of altering gait variability, which could have applications for using exoskeletons as rehabilitation devices. Further efforts could examine if it is possible to simultaneously reduce the LyE and FM at one or more lower limb joints.",
author = "Prokopios Antonellis and Samuel Galle and {De Clercq}, Dirk and Philippe Malcolm",
year = "2018",
month = "10",
doi = "10.1371/journal.pone.0205088",
language = "English (US)",
volume = "13",
journal = "PLoS One",
issn = "1932-6203",
publisher = "Public Library of Science",
number = "10",

}

TY - JOUR

T1 - Altering gait variability with an ankle exoskeleton

AU - Antonellis, Prokopios

AU - Galle, Samuel

AU - De Clercq, Dirk

AU - Malcolm, Philippe

PY - 2018/10

Y1 - 2018/10

N2 - Exoskeletons can influence human gait. A healthy gait is characterized by a certain amount of variability compared to a non-healthy gait that has more inherent variability; however which exoskeleton assistance parameters are necessary to avoid increasing gait variability or to potentially lower gait variability below that of unassisted walking are unknown. This study investigated the interaction effects of exoskeleton timing and power on gait variability. Ten healthy participants walked on a treadmill with bilateral ankle-foot exoskeletons under ten conditions with different timing (varied from 36% to 54% of the stride) and power (varied from 0.2 to 0.5 Wkg -1 ) combinations. We used the largest Lyapunov exponent (LyE) and maximum Floquet multiplier (FM) to evaluate the stride-to-stride fluctuations of the kinematic time series. We found the lowest LyE at the ankle and a significant reduction versus powered-off with exoskeleton power (summed for both legs) of 0.45 Wkg -1 and actuation timing at 48% of the stride cycle. at the knee, a significant positive effect of power and a negative interaction effect of power and timing were found for LyE. We found significant positive interaction effects of the square of timing and power for LyE at the knee and hip joints. In contrast, the FM at the ankle increased with increasing power and later timing. We found a significant negative effect of power and a positive interaction effect of power and timing for FM at the knee and no significant effects of any of the exoskeleton parameters for FM at the hip. The ability of the exoskeleton to reduce the LyE at the ankle joint offers new possibilities in terms of altering gait variability, which could have applications for using exoskeletons as rehabilitation devices. Further efforts could examine if it is possible to simultaneously reduce the LyE and FM at one or more lower limb joints.

AB - Exoskeletons can influence human gait. A healthy gait is characterized by a certain amount of variability compared to a non-healthy gait that has more inherent variability; however which exoskeleton assistance parameters are necessary to avoid increasing gait variability or to potentially lower gait variability below that of unassisted walking are unknown. This study investigated the interaction effects of exoskeleton timing and power on gait variability. Ten healthy participants walked on a treadmill with bilateral ankle-foot exoskeletons under ten conditions with different timing (varied from 36% to 54% of the stride) and power (varied from 0.2 to 0.5 Wkg -1 ) combinations. We used the largest Lyapunov exponent (LyE) and maximum Floquet multiplier (FM) to evaluate the stride-to-stride fluctuations of the kinematic time series. We found the lowest LyE at the ankle and a significant reduction versus powered-off with exoskeleton power (summed for both legs) of 0.45 Wkg -1 and actuation timing at 48% of the stride cycle. at the knee, a significant positive effect of power and a negative interaction effect of power and timing were found for LyE. We found significant positive interaction effects of the square of timing and power for LyE at the knee and hip joints. In contrast, the FM at the ankle increased with increasing power and later timing. We found a significant negative effect of power and a positive interaction effect of power and timing for FM at the knee and no significant effects of any of the exoskeleton parameters for FM at the hip. The ability of the exoskeleton to reduce the LyE at the ankle joint offers new possibilities in terms of altering gait variability, which could have applications for using exoskeletons as rehabilitation devices. Further efforts could examine if it is possible to simultaneously reduce the LyE and FM at one or more lower limb joints.

UR - http://www.scopus.com/inward/record.url?scp=85055604564&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85055604564&partnerID=8YFLogxK

U2 - 10.1371/journal.pone.0205088

DO - 10.1371/journal.pone.0205088

M3 - Article

C2 - 30356309

AN - SCOPUS:85055604564

VL - 13

JO - PLoS One

JF - PLoS One

SN - 1932-6203

IS - 10

M1 - e0205088

ER -