Article
Biophysics
James L. Williamson, Glen A. Lichtwark, Taylor J. M. Dick
Summary: This study explored the effects of passive ankle exoskeletons on neuromuscular control and muscle fascicle dynamics during vertical perturbations. The results demonstrated that exoskeleton assistance led to a reduction in muscle activation, an increase in fascicle length change, and a decrease in muscle forces. These changes have competing effects on the mechanics and energetics of lower limb muscles.
JOURNAL OF BIOMECHANICS
(2023)
Article
Biotechnology & Applied Microbiology
Benjamin A. Shafer, Sasha A. Philius, Richard W. Nuckols, James McCall, Aaron J. Young, Gregory S. Sawicki
Summary: Powered ankle exoskeletons can reduce metabolic cost by applying assistive torques with optimized timing and magnitude. Continuous adaptation of torque assistance is necessary for exoskeleton controllers. Using a neuromuscular model can help optimize the parameters of exoskeleton controllers for improved performance.
FRONTIERS IN BIOENGINEERING AND BIOTECHNOLOGY
(2021)
Article
Multidisciplinary Sciences
Paul S. Pridham, Leia Stirling
Summary: This paper presents two potential controllers for ankle exoskeletons based on soleus fascicles and Achilles tendon models. The methods use an estimate of the adenosine triphosphate hydrolysis rate of the soleus based on fascicle velocity. The controllers can generate distinct profiles for walking and running with speed variations.
Article
Engineering, Biomedical
William H. Clark, Richard E. Pimentel, Jason R. Franz
Summary: The study found that the biarticular gastrocnemius muscles play a more significant role than the uniarticular soleus in governing changes in forward propulsion during the mid to late stance phase of walking.
ANNALS OF BIOMEDICAL ENGINEERING
(2021)
Article
Engineering, Biomedical
Xiangyu Peng, Yadrianna Acosta-Sojo, Man Wu, Leia Stirling
Summary: This study aimed to evaluate people's sensitivity to changes in exoskeleton actuation timing and its associated ankle angle changes. Participants wore an active ankle exoskeleton and compared pairs of torque profiles with different actuation timings while walking on a treadmill. The results showed individual differences in sensitivity towards actuation timing and associated ankle angle changes, providing insights into how people perceive changes in exoskeleton control parameters.
IEEE TRANSACTIONS ON NEURAL SYSTEMS AND REHABILITATION ENGINEERING
(2022)
Article
Engineering, Biomedical
Santiago Canete, Elizabeth B. Wilson, Daniel A. Jacobs
Summary: Exoskeleton assistance can reduce metabolic cost and increase preferred walking speed, with individual outcomes varying. This study investigates the effects of a powered ankle exoskeleton on step regulation and its relationship to gait parameters. The results show that the response to assistance is closely related to the stepping strategy, especially in the initial learning stages.
IEEE TRANSACTIONS ON NEURAL SYSTEMS AND REHABILITATION ENGINEERING
(2023)
Article
Robotics
Woo-Seok Jang, Do-Yun Kim, Yun-Seok Choi, Yong-Jae Kim
Summary: The letter introduces a 2-DOF ankle-foot prosthesis with a compact size and low inertia, designed to provide comfortable walking with little effort for amputees. Using a parallel linkage mechanism and a unique spring mechanism, the prosthesis enhances walking propulsion without increasing foot mass. Placing heavy elements at the proximal part reduces inertia and metabolic cost, while capacitive type force sensors enable precise force measurement without adding mass to the foot. Overall, the effectiveness of the proposed prosthesis is verified through force sensor tests and preliminary walking tests on uneven ground.
IEEE ROBOTICS AND AUTOMATION LETTERS
(2021)
Article
Physiology
Eduardo Martinez-Valdes, Francesco Negro, Alberto Botter, Patricio A. Pincheira, Giacinto Luigi Cerone, Deborah Falla, Glen A. Lichtwark, Andrew G. Cresswell
Summary: The integration of electromyography (EMG) and ultrasound imaging has provided important insights into muscle activation and contraction mechanisms. This study demonstrates the relationship between tibialis anterior muscle (TA) motor unit discharge, fascicle length, and dorsiflexion torque using ultrasound-transparent high-density EMG electrodes. The findings highlight the interplay between neural drive, muscle contraction, and torque during sustained isometric contractions.
JOURNAL OF APPLIED PHYSIOLOGY
(2022)
Article
Engineering, Biomedical
Taimoor Afzal, Fangshi Zhu, Shih-Chiao Tseng, John A. Lincoln, Gerard E. Francisco, Hao Su, Shuo-Hsiu Chang
Summary: Exoskeleton-assistance does not alter the existing synergy modules, but could induce a new module to emerge, and alters the control of these modules, i.e., modifies the neural commands indicated by the reduced amplitude of the activation profiles.
IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING
(2022)
Article
Engineering, Biomedical
Di Hu, Caihua Xiong, Tao Wang, Tiancheng Zhou, Jiejunyi Liang, Yuhao Li
Summary: The human musculoskeletal system has evolved and developed to perform cushioning and impulsive functions during walking. However, the efficiency of energy interaction between foot structure and ankle joint in the human body is lacking, limiting economical walking potential. A study has shown that an unpowered exoskeleton robot can reduce metabolic expenditure by modulating energy in the foot-ankle complex, improving energy efficiency of walking.
IEEE TRANSACTIONS ON NEURAL SYSTEMS AND REHABILITATION ENGINEERING
(2022)
Article
Engineering, Biomedical
Ying Fang, Zachary F. Lerner
Summary: The study developed a real-time biofeedback mechanism and set step length as the target to effectively improve gait mechanics in individuals with CP when using wearable ankle assistance.
IEEE TRANSACTIONS ON NEURAL SYSTEMS AND REHABILITATION ENGINEERING
(2021)
Article
Chemistry, Analytical
Dmitry S. Zhvansky, Francesca Sylos-Labini, Arthur Dewolf, Germana Cappellini, Andrea d'Avella, Francesco Lacquaniti, Yury Ivanenko
Summary: This article introduces the PEPATO software, which is a benchmarking solution for assessing changes in the spinal locomotor output during walking in exoskeletons. The software maps functional and structural changes at the spinal cord level into muscle synergies and spinal maps of motoneuron activity, and provides a set of performance indicators as output. By analyzing the EMG activity from lower limb muscles, the software can detect specific muscle activation modules and spinal motor pools, as well as demonstrate differential adaptation in walking with an unloading exoskeleton.
Article
Biology
Kirsty A. McDonald, Joseph P. Cusumano, Andrew Hieronymi, Jonas Rubenson
Summary: This study found that humans are more inclined to avoid excessive muscle activation and fatigue during walking rather than minimizing energy expenditure. Muscle activation costs are more closely related to metabolic energy use, and people also minimize muscle activation when choosing walking patterns. This research provides empirical evidence of non-energetic optimization in human walking behavior.
PROCEEDINGS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES
(2022)
Article
Engineering, Biomedical
Cunjin Wang, Lei Dai, Donghua Shen, Jiyuan Wu, Xingsong Wang, Mengqian Tian, Yunde Shi, Chun Su
Summary: This study presents the design and functionality of a quasi-passive ankle exoskeleton that captures heel-strike energy loss and recycles it into propulsion. The prototype showed good functionality on level ground but had limitations on inclined surfaces.
IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING
(2022)
Article
Biotechnology & Applied Microbiology
Kaifan Xie, Yueling Lyu, Xianyi Zhang, Rong Song
Summary: Increasing surface compliance affects both ankle moment and stiffness regulations during walking. The ankle moment increases to prevent lower limb collapse, while ankle stiffness increases to maintain stability during the mid-stance phase of gait.
FRONTIERS IN BIOENGINEERING AND BIOTECHNOLOGY
(2021)
Article
Engineering, Biomedical
Richard W. Nuckols, Gregory S. Sawicki
JOURNAL OF NEUROENGINEERING AND REHABILITATION
(2020)
Article
Multidisciplinary Sciences
Richard W. Nuckols, Kota Z. Takahashi, Dominic J. Farris, Sarai Mizrachi, Raziel Riemer, Gregory S. Sawicki
Article
Robotics
R. W. Nuckols, S. Lee, K. Swaminathan, D. Orzel, R. D. Howe, C. J. Walsh
Summary: Variability in human walking is influenced by individual physiology, environment, and task requirements. A muscle-based assistance strategy utilizing direct measurements of muscle dynamics during specific tasks can significantly reduce metabolic demand and potentially support the adoption of wearable robotics in real-world applications.
Article
Robotics
Dylan G. Schmitz, Richard W. Nuckols, Sangjun Lee, Tunc Akbas, Krithika Swaminathan, Conor J. Walsh, Darryl G. Thelen
Summary: Exosuits have the potential to assist locomotion in both healthy and pathological populations, but their effect on muscle-tendon loading is not yet fully understood. This study used shear wave tensiometers to measure Achilles tendon force and found that ankle exosuit assistance reduced peak Achilles tendon force. The relationship between tendon force and ankle torque was no longer significant when ankle plantarflexor assistance was applied.
Article
Chemistry, Analytical
Letizia Gionfrida, Richard W. Nuckols, Conor J. Walsh, Robert D. Howe
Summary: In the field of wearable robotics, personalized assistance is important for maximizing benefits. This study introduces and validates a model for extracting muscle fascicle lengths in young and older adults using ultrasound imaging. Despite the impact of age-related muscle loss, the small variation in individual fascicle error suggests that it may be acceptable for generating assistive force profiles.
Article
Multidisciplinary Sciences
Richard W. Nuckols, Chih-Kang Chang, Daekyum Kim, Asa Eckert-Erdheim, Dorothy Orzel, Lauren Baker, Teresa Baker, Nicholas C. Wendel, Brendan Quinlivan, Patrick Murphy, Jesse Grupper, Jacqueline Villalobos, Louis N. Awad, Terry D. Ellis, Conor J. Walsh
Summary: Chronic impairment in the paretic ankle following stroke often requires the use of compensatory patterns, such as asymmetric propulsion, for effective walking. Ankle exosuit assistance can provide biomechanical benefits, but practice in lab settings is limited. This study combines community training with exosuit assistance to improve gait training and rehabilitation.
ANNALS OF THE NEW YORK ACADEMY OF SCIENCES
(2023)
Article
Engineering, Biomedical
Evelyn J. Park, Tunc Akbas, Asa Eckert-Erdheim, Lizeth H. Sloot, Richard W. Nuckols, Dorothy Orzel, Lexine Schumm, Terry D. Ellis, Louis N. Awad, Conor J. Walsh
IEEE TRANSACTIONS ON MEDICAL ROBOTICS AND BIONICS
(2020)