Identify which age–sex groups are represented by widely used OpenSim lower-limb models

Identify which specific sex and age groups are adequately represented by the commonly used open-source OpenSim lower-limb musculoskeletal models—Delp 1990 (Model D), Gait2392/2354 (Model G), Arnold 2010 (Model A), London Lower Limb (Model L), and Rajagopal 2016 (Model R)—in terms of physiological cross-sectional area and muscle mass distributions that determine maximum isometric force parameters.

Background

The paper reviews experimentally derived lower-limb muscle parameters (PCSA, muscle mass, and relative muscle mass) across sex and age groups and compares them to parameters used in the most frequently downloaded open-source OpenSim models. Because many studies scale models without adjusting PCSA-derived maximum isometric forces for demographics, there is a risk of misrepresenting muscle force distributions in specific populations.

Although the paper provides evidence of sex- and age-related differences in relative muscle mass and highlights inconsistencies across popular OpenSim models (Delp 1990, Gait2392/2354, Arnold 2010, London Lower Limb, Rajagopal 2016), the authors explicitly state that it remains unclear which demographic groups these models adequately represent. Resolving this is necessary for demographically appropriate model selection and scaling.