PhD Defence Robbert Middelaar | From impact to action: an inverse dynamics approach for estimating total ankle forces in outdoor running using inertial sensors

From impact to action: an inverse dynamics approach for estimating total ankle forces in outdoor running using inertial sensors

Robbert Middelaar is a PhD student in the department Biomedical Signals and Systems. (Co)promotors are prof.dr.ir. P.H.Veltink and dr. J. Reenalda from the faculty of Electrical Engineering, Mathematics and Computer Science (EEMCS), University of Twente.

Running is one of the most popular sports activities in the world and provides physical and mental health benefits. However, running is also associated with a high incidence of (overuse) injuries. Given its global popularity, monitoring runners and understanding the aetiology of injuries is essential for injure prevention.

To understand the repetitive character of running, impact-related parameters such as peak tibial acceleration (PTA) are commonly used. However, these reflect only external impact forces and not total joint force, which also includes muscle contributions. Because tissue fatigue life is strongly influenced by active (muscle) forces, these may be more relevant than impact measures only. Incorporating active (muscle) forces is therefore important for a comprehensive understanding of running-related injuries, especially in an outdoor, sports-specific setting.

Inverse dynamics is a method for estimating joint forces and moments, which typically requires gold standard measurement systems. However, these systems are impractical in outdoor settings. Inertial measurement units (IMUs) provide a feasible alternative due to their ease of use in real-world scenarios. The aim of this thesis is to advance motion analysis methods in sports-specific settings using IMUs, allowing a more comprehensive analysis of both impact and active (muscle) forces during outdoor running.

Chapter 2 focuses on PTA and tibial impulse, by using a standardised IMU-based method to obtain impact-acceleration only. Chapter 3 demonstrates that a top-down inverse dynamics approach using IMUs can accurately estimate knee moments. Chapter 4 introduces a method to estimate anteroposterior CoP from a single tibial IMU, enabling accurate sagittal ankle moment and total ankle force estimation with only three IMUs. Chapter 5 combines these methods outdoors, showing increases in impact measures during fatigue while active forces remained stable, highlighting their distinct behaviours.

This dissertation contributes to the growing interest in using IMUs in uncontrolled settings. These studies provide a foundation for research into running-related injuries, where the interaction between impact and active (muscle) forces at the ankle joint can be estimated and evaluated using a simple three-IMU setup in an outdoor environment.