Sureshkumar, H. | Search bioRxiv

bioRxiv2026

Estimating Body Segment Properties for Adults AcrossDiverse Body Morphologies: A Data-Driven GeometricFramework

Accurate estimation of body segment inertial properties is essential for biomechanical analyses, yet commonly used scaling methods rely on limited datasets and do not generalize well across diverse adult body morphologies. We developed a data-driven framework that estimates segment lengths, masses, centers of mass, and moments of inertia using regression models trained on large anthropometric datasets (ANSUR II and NHANES) combined with a geometric representation of 16 body segments. The framework uses height, weight, and sex as primary inputs and incorporates waist and hip circumferences or other length and cross-sectional measurements when available to refine body-shape predictions. For individuals with obesity, additional geometric rules redistribute excess mass based on segment-specific volume changes. The resulting models reproduced segment lengths, cross-sectional dimensions, and lumped segment masses within the ranges observed in the training datasets and outperformed published regression equations, particularly at higher body mass index (BMI) values. To promote broad adoption, we provide an open-source API in Python that performs the full parameter estimation using the trained models. This framework offers an accurate and accessible method for estimating adult body segment properties across a wide range of body sizes and shapes, supporting improved motion analysis, musculoskeletal simulation, and clinical biomechanics.

bioengineering↗

bioRxiv2024

Signatures of glassy dynamics in highly ordered lipid bilayers with emergence of soft dynamic channels

Over the last few decades, extensive investigations on spatial and dynamic heterogeneity have been performed on carefully reconstituted biological lipid membranes. Characterising the molecular features in heterogeneous membranes is extremely challenging due to experimentally inaccessible time- and length-scales of these emergent systems. In this context, simulations can provide important insights into molecular-level interactions leading to membrane heterogeneity and associated functions. To that end, we use the non-affine displacement (NAD) framework (a concept borrowed from Physics of granular material) to faithfully capture molecular-scale local membrane order in simulated heterogeneous bilayers. In our latest application of NAD, we investigate the temperature-dependent spatial and temporal organisation on microseconds trajectories of liquid-ordered bilayer systems at all-atom resolution (DPPC/DOPC/CHOL: 0.55:0.15:0.30; 40 nm x 40 nm with a total of 5600 lipids and 2 million atoms). Lateral organisation in these large bilayer patches show noticeable dynamic heterogeneity despite their liquid-ordered nature. Moreover, our NAD analyses reveal soft fluid channels within the tightly packed membrane reminiscent of the classical two-component Kob-Andersen glass-forming binary mixture. Hence, we characterised these systems using classical glass physics markers for dynamic heterogeneities such as Overlap, Four-point Susceptibility, van Hove, and Intermediate Scattering functions to quantify the multiple time scales underlying the lipid dynamics. Our analyses reveal that highly ordered membrane systems can have glass-like dynamics with distinct soft fluid channels inside them. Biologically, these dynamic channels could act as conduits for facilitating molecular encounters for biological functions even in highly ordered phases such as lipid nanodomains and rafts. SignificanceLiquid-ordered lipid membrane offers a reliable representation of the cholesterolrich outer leaflet of the plasma membrane. We show that dynamic heterogeneity is present even in highly ordered phases of lipid membrane, which arise at equilibrium merely from thermal fluctuations. Membranes in this state act as strong glass formers, and are hence less susceptible to temperature fluctuations. The dynamics is faster than actin or proteinmediated reorganisation and presence of passive but dynamic "soft channels" amidst the highly ordered lipid environment suggests a new exciting possibility that these channels could act as fast conduits for molecular encounters on the robust membrane surface.

biophysics↗