TY - JOUR

T1 - Neuromuscular characterisation in Cerebral Palsy using hybrid Hill-type models on isometric contractions

AU - Wiedemann, L. G.

AU - Jayaneththi, V. R.

AU - Kimpton, J.

AU - Müller, Matthias A.

AU - Wilson, N. C.

AU - Mcdaid, A. J.

AU - Chan, A.

AU - Hogan, A.

AU - Lim, E.

N1 - Funding information: This research was supported by the Marsden Fund (reference number: 3706165 ), managed by the Royal Society of New Zealand. The funding source did not have any involvement in the study design, data collection, analysis, interpretation of the data, writing of the report and in the decision to submit the work for publication.

PY - 2018/12/1

Y1 - 2018/12/1

N2 - Background: Muscles of individuals with Cerebral Palsy (CP) undergo structural changes over their lifespan including an increase in muscle stiffness, decreased strength and coordination. Being able to identify these changes non-invasively would be beneficial to improve understanding of CP and assess therapy effectiveness over time. This study aims to adapt an existing EMG-driven Hill-type muscle model for neuromuscular characterisation during isometric contractions of the elbow joint. Methods: Participants with (n = 2) and without CP (n = 8) performed isometric force ramps with contraction levels ranging between 15 and 70% of their maximum torque. During these contractions, high-density EMG data were collected from the M. Biceps and Triceps brachii with 64 electrodes on each muscle. The EMG-driven Hill-type muscle model was used to predict torques around the elbow joint, and muscle characterisation was performed by applying a genetic algorithm that tuned individuals’ parameters to reduce the RMS error between observed and predicted torque data. Results: Observed torques could be predicted accurately with an overall mean error of 1.24Nm ± 0.53Nm when modelling individual force ramps. The first four parameters of the model could be identified relatively reliably across different experimental protocols with a full-scale variation of below 20%. Conclusion: An HD-EMG muscle modelling approach to evaluating neuromuscular properties in participants with and without CP has been presented. This pilot study confirms the feasibility of the experimental protocol and demonstrates some parameters can be identified robustly using the isometric contraction force ramps.

AB - Background: Muscles of individuals with Cerebral Palsy (CP) undergo structural changes over their lifespan including an increase in muscle stiffness, decreased strength and coordination. Being able to identify these changes non-invasively would be beneficial to improve understanding of CP and assess therapy effectiveness over time. This study aims to adapt an existing EMG-driven Hill-type muscle model for neuromuscular characterisation during isometric contractions of the elbow joint. Methods: Participants with (n = 2) and without CP (n = 8) performed isometric force ramps with contraction levels ranging between 15 and 70% of their maximum torque. During these contractions, high-density EMG data were collected from the M. Biceps and Triceps brachii with 64 electrodes on each muscle. The EMG-driven Hill-type muscle model was used to predict torques around the elbow joint, and muscle characterisation was performed by applying a genetic algorithm that tuned individuals’ parameters to reduce the RMS error between observed and predicted torque data. Results: Observed torques could be predicted accurately with an overall mean error of 1.24Nm ± 0.53Nm when modelling individual force ramps. The first four parameters of the model could be identified relatively reliably across different experimental protocols with a full-scale variation of below 20%. Conclusion: An HD-EMG muscle modelling approach to evaluating neuromuscular properties in participants with and without CP has been presented. This pilot study confirms the feasibility of the experimental protocol and demonstrates some parameters can be identified robustly using the isometric contraction force ramps.

KW - Cerebral palsy

KW - Electromyography

KW - Force ramp

KW - HD-EMG

KW - Hill-type muscle model

KW - Isometric contraction

KW - Musculoskeletal modelling

KW - Neuromuscular characterisation

UR - http://www.scopus.com/inward/record.url?scp=85056205303&partnerID=8YFLogxK

U2 - 10.1016/j.compbiomed.2018.10.027

DO - 10.1016/j.compbiomed.2018.10.027

M3 - Article

VL - 103

SP - 269

EP - 276

JO - Computers in Biology and Medicine

JF - Computers in Biology and Medicine

SN - 0010-4825

ER -