This release is related to the recent study by Akhavanfar et al. (2023), in which we improved the fully articulated thoracolumbar spine (FATLS) model originally proposed by Bruno et al. (2015). Our enhancements involve incorporating passive stiffness considerations and adding kinematic constraints to make the model suitable for dynamic tasks. We validated the spinal forces estimated by our model for nine dynamic lifting and lowering tasks, expanding beyond the validation scope of previous spine musculoskeletal models. Furthermore, we conducted an investigation to determine which external hand forces and moments (EHF&M) modeling approach (referencing our first release) provides the most accurate spinal load estimates when utilizing our enhanced OpenSim FATLS model. The first "download link" below (NewFATLSModelValidation.rar) includes the newly developed spine model for OpenSim, along with sample setup files and MATLAB scripts designed to automatically generate the necessary models and motion files required for kinematic and dynamic analysis of EHF&M Approaches 3–5. Please note that the model was created in OpenSim 3.3, and as a result, the scripts are designed to use the API for OpenSim 3.3. However, the model can be used in more recent versions, such as OpenSim 4.4. The methods required for utilizing the EHF&M approaches within any models are fully described in our previous paper (Akhavanfar et al., 2022), thus users can employ these methods with the model in recent OpenSim versions. The second "download link" below (NewFATLSModelValidation-OpenSim4_4.rar) includes all the same files as above, but the scripts were updated for use with OpenSim 4.4 and were translated into Python. We strongly recommend carefully reading the README.pdf document before using the files provided in this release.  View License