Colloquium announcement

Faculty of Engineering Technology

Department Biomechanical Engineering
Master programme Mechanical Engineering

As part of his / her masterassignment

Noor Ooms

will hold a speech entitled:

The influence of muscle deformation on the muscle moment arm



Models of the human musculoskeletal system are used to better understand the dysfunctions of the system, and to try to improve the diagnosis and treatment for patients. The models are also used for the design of rehabilitation applications, prosthetics and orthoses. The current musculoskeletal model results are not reliable enough for critical personalized applications and surgeries. This can be caused by multiple things, one of which is investigated here; the influence of the muscle deformation during contraction on the muscle moment arm.

Most currently existing models keep the moment arm of the muscle force with respect to the joint as a constant value. However, results extracted from ultrasound and MRI images show that the moment arm does change. By keeping the moment arm as a constant, it will be underestimated while the muscle is contracting. This causes an overestimation of the developed muscle force. This will give deviations in the input values for the rehabilitation applications, prosthetics and orthoses which result in a treatment that is not optimal for the patient.

In this thesis a model is created which models the change in moment arm that occurs when a muscle acts upon a joint. The law of conservation of volume, the effect of the force-length relationship of a muscle and the effect of the activation of the muscle are taken into account. A method to improve the accuracy of the simulations is presented and validated using previous results from literature. It can be concluded that the influence of the changing muscle thickness is not significant.