Conjoint Associate Lecturer, UNSW Graduate School of Biomedical Engineering
+612 9399 1832
Dr Bart Bolsterlee is a mechanical engineer (BSc) and biomedical engineer (MSc, PhD) who studies the generation of force and movement in humans. His specialty is the use of imaging technologies such as MRI and ultrasound to study human movement biomechanics. In 2014 he completed his PhD in biomechanical modelling of the human upper limb at Delft University of Technology (The Netherlands). His current work at NeuRA focuses on the use of diffusion tensor imaging (DTI; an MRI technique) to measure muscle structure. He has recently developed novel algorithms to obtain quantitative measurements of muscle architecture by combining information from anatomical MRI and DTI scans. He applies these techniques to study mechanisms of muscle contracture (stiffening of muscles) in patients with stroke and cerebral palsy. He also performs studies in basic muscle physiology and biomechanics to elucidate the mechanical role of active and passive structures in muscles, and to study how muscles change shape following exercise.
Dr Bart Bolsterlee’s work has been published in high-quality journals such as Journal of Biomechanics, Journal of Applied Physiology and PlosONE. He is the secretary/treasurer of the Australian and New Zealand Society of Biomechanics.
DR MARTIN HEROUX Research Officer
DR PETER STUBBS Research Officer
Determination of skeletal muscle architecture is important for accurately modeling muscle behavior. Current methods for 3D muscle architecture determination can be costly and time-consuming, making them prohibitive for clinical or modeling applications. Computational approaches such as Laplacian flow simulations can estimate muscle fascicle orientation based on muscle shape and aponeurosis location. The accuracy of this approach is unknown, however, since it has not been validated against other standards for muscle architecture determination. In this study, muscle architectures from the Laplacian approach were compared to those determined from diffusion tensor imaging in eight adult medial gastrocnemius muscles. The datasets were subdivided into training and validation sets, and computational fluid dynamics software was used to conduct Laplacian simulations. In training sets, inputs of muscle geometry, aponeurosis location, and geometric flow guides resulted in good agreement between methods. Application of the method to validation sets showed no significant differences in pennation angle (mean difference [Formula: see text] or fascicle length (mean difference 0.9 mm). Laplacian simulation was thus effective at predicting gastrocnemius muscle architectures in healthy volunteers using imaging-derived muscle shape and aponeurosis locations. This method may serve as a tool for determining muscle architecture in silico and as a complement to other approaches.
There are few comprehensive investigations of the changes in muscle architecture that accompany muscle contraction or change in muscle length in vivo. For this study, we measured changes in the three-dimensional architecture of the human medial gastrocnemius at the whole muscle level, the fascicle level and the fiber level using anatomical MRI and diffusion tensor imaging (DTI). Data were obtained from eight subjects under relaxed conditions at three muscle lengths. At the whole muscle level, a 5.1% increase in muscle belly length resulted in a reduction in both muscle width (mean change -2.5%) and depth (-4.8%). At the fascicle level, muscle architecture measurements obtained at 3,000 locations per muscle showed that for every millimeter increase in muscle-tendon length above the slack length, average fascicle length increased by 0.46 mm, pennation angle decreased by 0.27° (0.17° in the superficial part and 0.37° in the deep part), and fascicle curvature decreased by 0.18 m(-1) There was no evidence of systematic variation in architecture along the muscle's long axis at any muscle length. At the fiber level, analysis of the diffusion signal showed that passive lengthening of the muscle increased diffusion along fibers and decreased diffusion across fibers. Using these measurements across scales, we show that the complex shape changes that muscle fibers, whole muscles, and aponeuroses of the medial gastrocnemius undergo in vivo cannot be captured by simple geometrical models. This justifies the need for more complex models that link microstructural changes in muscle fibers to macroscopic changes in architecture.NEW & NOTEWORTHY Novel MRI and DTI techniques revealed changes in three-dimensional architecture of the human medial gastrocnemius during passive lengthening. Whole muscle belly width and depth decreased when the muscle lengthened. Fascicle length, pennation, and curvature changed uniformly or near uniformly along the muscle during passive lengthening. Diffusion of water molecules in muscle changes in the same direction as fascicle strains.