TY - JOUR
T1 - Adapting to the Mechanical Properties and Active Force of an Exoskeleton by Altering Muscle Synergies in Chronic Stroke Survivors
AU - Rinaldi, Linda
AU - Yeung, Ling Fung
AU - Lam, Patrick Chi Hong
AU - Pang, Marco Y.C.
AU - Tong, Raymond Kai Yu
AU - Cheung, Vincent C.K.
N1 - Funding Information:
Manuscript received December 15, 2019; revised April 9, 2020 and June 14, 2020; accepted July 16, 2020. Date of publication August 17, 2020; date of current version October 8, 2020. The work of Vincent C. K. Cheung was supported in part by the CUHK Faculty of Medicine Faculty Innovation Award under Grant FIA2016/A/04, in part by the CUHK Group Research Scheme under Grant NL/JW/rc/grs1819/0426/19hc, and in part by the Hong Kong Research Grants Council under ECS Grant 24115318 and RIF Grant CUHK-R4022-18. (Corresponding author: Vincent C. K. Cheung.) Linda Rinaldi, Patrick Chi-Hong Lam, and Vincent C. K. Cheung are with the School of Biomedical Sciences, The Chinese University of Hong Kong, Hong Kong, and also the Gerald Choa Neuroscience Centre, The Chinese University of Hong Kong, Hong Kong (e-mail: Rinaldi.Linda@link.cuhk.edu.hk; patzzz@hotmail.com; vckc@ cuhk.edu.hk).
Publisher Copyright:
© 2020 IEEE.
PY - 2020/10
Y1 - 2020/10
N2 - Chronic stroke survivors often suffer from gait impairment resistant to intervention. Recent rehabilitation strategies based on gait training with powered exoskeletons appear promising, but whether chronic survivors may benefit from them remains controversial. We evaluated the potential of exoskeletal gait training in restoring normal motor outputs in chronic survivors (N = 10) by recording electromyographic signals (EMGs, 28 muscles both legs) as they adapted to exoskeletal perturbations, and examined whether any EMG alterations after adaptation were underpinned by closer-to-normal muscle synergies. A unilateral ankle-foot orthosis that produced dorsiflexor torque on the paretic leg during swing was tested. Over a single session, subjects walked overground without exoskeleton (FREE), then with the unpowered exoskeleton (OFF), and finally with the powered exoskeleton (ON). Muscle synergies were identified from EMGs using non-negative matrix factorization. During adaptation to OFF, some paretic-side synergies became more dissimilar to their nonparetic-side counterparts. During adaptation to ON, in half of the subjects some paretic-side synergies became closer to their nonparetic references relative to their similarity at FREE as these paretic-side synergies became sparser in muscle components. Across subjects, level of inter-side similarity increase correlated negatively with the degree of gait temporal asymmetry at FREE. Our results demonstrate the possibility that for some survivors, exoskeletal training may promote closer-to-normal muscle synergies. But to fully achieve this, the active force must trigger adaptive processes that offset any undesired synergy changes arising from adaptation to the device's mechanical properties while also fostering the reemergence of the normal synergies.
AB - Chronic stroke survivors often suffer from gait impairment resistant to intervention. Recent rehabilitation strategies based on gait training with powered exoskeletons appear promising, but whether chronic survivors may benefit from them remains controversial. We evaluated the potential of exoskeletal gait training in restoring normal motor outputs in chronic survivors (N = 10) by recording electromyographic signals (EMGs, 28 muscles both legs) as they adapted to exoskeletal perturbations, and examined whether any EMG alterations after adaptation were underpinned by closer-to-normal muscle synergies. A unilateral ankle-foot orthosis that produced dorsiflexor torque on the paretic leg during swing was tested. Over a single session, subjects walked overground without exoskeleton (FREE), then with the unpowered exoskeleton (OFF), and finally with the powered exoskeleton (ON). Muscle synergies were identified from EMGs using non-negative matrix factorization. During adaptation to OFF, some paretic-side synergies became more dissimilar to their nonparetic-side counterparts. During adaptation to ON, in half of the subjects some paretic-side synergies became closer to their nonparetic references relative to their similarity at FREE as these paretic-side synergies became sparser in muscle components. Across subjects, level of inter-side similarity increase correlated negatively with the degree of gait temporal asymmetry at FREE. Our results demonstrate the possibility that for some survivors, exoskeletal training may promote closer-to-normal muscle synergies. But to fully achieve this, the active force must trigger adaptive processes that offset any undesired synergy changes arising from adaptation to the device's mechanical properties while also fostering the reemergence of the normal synergies.
KW - Chronic stroke
KW - electromyography
KW - exoskeleton
KW - gait impairment
KW - muscle synergy
UR - http://www.scopus.com/inward/record.url?scp=85092452177&partnerID=8YFLogxK
U2 - 10.1109/TNSRE.2020.3017128
DO - 10.1109/TNSRE.2020.3017128
M3 - Journal article
C2 - 32804652
AN - SCOPUS:85092452177
VL - 28
SP - 2203
EP - 2213
JO - IEEE Transactions on Neural Systems and Rehabilitation Engineering
JF - IEEE Transactions on Neural Systems and Rehabilitation Engineering
SN - 1534-4320
IS - 10
M1 - 9169666
ER -