## 2 Materials and Methods  
MMD-MSD was designed and collected for the needs of the ErgoResearch project (the ErgoResearch project, entitled \"Ergonomic research on work-related health problems by innovative computer models with a focus on the prevention of Musculoskeletal Disorders\", was funded by the Bulgarian National Science Fund under contract KP-06-N37/1 (December 2019-March 2024)), which, among other goals, aims at the creation of resources (datasets, software, models) in support of research and technology development (RTD) that helps prevent MSDs. The data collection was based on photogrammetry, as this provides a nonintrusive way to assess the human body's posture in various scenarios, and a wearable wristband for the acquisition of peripheral physiological signals.  
The focus of the MMD-MSD data collection process aimed at implementing an experimental setup and scenarios that allow for assessing the performance of a person while working in a typical office scenario. This involves a person sitting on an office chair next to an office desk equipped with a desktop computer configuration with standard interface devices, such as a monitor, keyboard, and mouse. The dataset comprises scenarios involving people sitting in a spontaneous posture--the one that a sitting person takes naturally while concentrating on computer-bound tasks--in contrast to the scenario when the body's position is manually adjusted by a medical doctor, who specializes in the field of MSD rehabilitation, to sitting in the recommended ergonomic, health-friendly posture. Moreover, each participant was instructed on how to keep a proper ergonomic posture while working with the specific desktop computer configuration. For capturing the person-specific body structure, the dataset also registered spontaneous and corrected standing positions, which were adjusted with the help of a physiotherapist in en-face and profile perspectives.  
To elicit spontaneous sitting positions, we engaged the volunteers in various computer-based tasks, starting with filling in a questionnaire, completing the Stroop test, and discussing their experiences during the data collection process. Here, we made use of the Stroop test as a low-complexity mental task, which does not induce a high cognitive load but requires concentration and attention. In the Stroop tests, we started with a low-complexity stimulus and subsequently alternated episodes with lower and higher difficulty to motivate the volunteers to pay more attention.  
Each participant completed the Stroop test twice: when the person was sitting on an office chair without and with an air-cushioned stability disk placed on the chair. The air-cushioned disk requires the person to maintain balance, which is feasible only when sitting in a proper working posture. Thus, here, we consider the scenario when people were using the air-cushioned disk to enforce proper sitting posture. When the stability disk was not used, we recorded each volunteer's performance on the Stroop test when sitting in spontaneous and manually corrected body positions.  
Finally, we ought to mention that for the 100 recruited volunteers involved in the database creation, who were mostly students and university staff, we deemed that the observed differences in individual performance were primarily due to differences in their concentration and attention during the Stroop tests and should not be interpreted as linked to their person-specific cognitive capacity.  
In the following subsections, we outline the data collection setup, protocol, types of data and their tagging, and the dataset organization and file formats.