Paediatric biomechanical modelling techniques: Thomas Korff and Florian Fath
When conducting research to understand the mechanisms underlying age-related changes in motor behaviour, the analysis of muscular forces and torques (rotational forces) can give us unique insights into the nervous system’s strategies to achieve the task of interest (Winter and Eng 1995). As the direct measurement of internal muscle forces is invasive and unethical, researchers use musculoskeletal models to estimate them indirectly. In general, two particular modelling techniques (inverse and forward dynamics) are common tools, which help researchers to estimate muscle forces and torques indirectly. The goal of both inverse and forward dynamics is to estimate muscle forces or torques from non-invasive biomechanical measures such as joint kinematics (typically obtained from motion analysis) and ground reaction forces (typically obtained from force platforms or similar devices). Both techniques require a range of input parameters relating to the properties of the musculoskeletal system. These parameters can be broadly divided into those relating to segmental inertia and those relating to muscletendon mechanics. In order to obtain valid outputs from biomechanical models, it is important to use accurate input parameters. In this chapter, we discuss the basic concepts of both inverse and forward dynamics, and we give an overview of the input parameters required for each modelling technique. We will then discuss developmental aspects of these input parameters and their implications relating to developmental research.