Quantification of trunk muscle forces through multibody models and non-invasive experimental measurements by Simon Hinnekens

In biomechanics, spine modelling allows the calculation of intervertebral efforts. The latter reflect the combined effect of spine geometry, spine kinematics and muscle forces. Although the geometry and kinematics of the spine are well known, the estimation of muscle forces is still one of the major challenges in spine modelling. For their quantification, hybrid approaches may be a good opportunity to consider the individual muscle strategy, thanks to electromyography (EMG) signals from an upfront experiment as input to the model. In this work, a novel hybrid approach is proposed, by focusing on static configurations and consequently neglecting the muscle dynamics. The hybrid approach relies on a well thought experiment and protocol to ensure that the EMG signals are sufficiently reliable to be used. A multibody model associated with the experiment was developed to compute muscle forces and intervertebral efforts.

The hybrid approach was developed in two steps. First, it was proposed to use a relatively simple EMG-based distribution of a global equivalent force, distributed over all the muscle fascicles included in the model. Secondly, it was proposed to embed EMG signals into the optimisation process via constraint functions or by modifying the cost functions. Overall, the hybrid approach showed promising results with intervertebral efforts close to those obtained with purely optimisation-based solutions, while computing muscles forces more representative of the recorded muscle strategies.

This thesis highlights the use of hybrid approaches to quantify trunk muscle forces for static configurations. Hybrid approaches provide a good alternative to mathematical approaches to improve muscle force estimation and account for the diversity of muscle strategies.

Jury members :

• Prof. Paul Fisette (UCLouvain, Belgium), supervisor
• Prof. Christine Detrembleur (UCLouvain, Belgium), supervisor
• Prof. Hervé Jeanmart (UCLouvain, Belgium), chairperson
• Prof. Philippe Mahaudens (UCLouvain, Belgium)
• Prof. Maxime Raison (Polytechnique Montréal, Canada)
• Prof. François Glineur (UCLouvain, Belgium)
• Dr. Raphaël Dumas (Université Gustave Eiffel, Université Claude Bernard Lyon 1, France)

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