# Development of a Simplified Human Body Model for Movement Simulations
## 4 Discussion  
The main objective of this research was to develop a simplified model of the human body movement system that could be used to simulate movement and to analyze the kinematic and dynamic parameters present during the performance of various activities. The developed model consists of simplified geometric solids that are mostly connected by spherical joints. On the basis of anthropometric data, a comprehensive set of equations was formulated that parameterized each segment's dimensions and mass with regard to only two body measurements (height and mass). Subsequently, for testing and evaluation, the model was built in Adams software as a 3D dynamic numerical model, based on an example height of 187 cm and a body mass of 70 kg. This enabled the simulation of movement and detailed analysis. The movement was reproduced with data obtained from an experiment with a volunteer who was lifting an object from the ground with both hands with a bent spine. The measurement was performed using a set of inertial sensors with software (STT iSen IMU system). Overall, the IMU system worked properly and showed correctly measured movements, but in the case of some body parts with significant rotations in three dimensions, the exported data (joint biomechanical angles) had some inaccuracies caused by the manufacturer's software calculation method. In these few cases, it was necessary to apply a correction to the obtained values so that the final effect would be as close to reality as possible. This solution was chosen because applying a correction to a movement measurement was simpler and provided better results (closer to reality) than the attempts to completely independently reproduce the desired movement. In order to accurately and correctly reproduce human movement, three motions based on the measured biomechanical angles (from the IMU system) were applied to each joint in the model. The implemented movement enabled the analysis of the kinematic and dynamic parameters of the human body, such as displacements, velocities, and angular accelerations, as well as the moments of force occurring in individual joints. The obtained values were consistent with the theoretical expectations and assumptions. Therefore, despite the need for further experimental validation of the findings, this proves that  
* the developed model can be correctly used for the analysis of human movement;
* the built-in Adams exemplary numerical model is suitable for simulating and visualizing motion, thus enabling not only angular displacements in joints but also angular velocities and moments of forces between body parts to be obtained;
* the data from the IMU system can be applied to the model as input data for simulating the desired/measured movement. The ideal model should be characterized by having a structure and shapes of segments as simplified as possible while at the same time maintaining the body element's dimensions, COM positions, and ranges of motion. This would ensure that the simulations are easy to perform and also provide accurate results. The model developed in this work was created based on existing methods of presenting the human musculoskeletal system--it reproduces body parts in a simplified way, focusing mainly on the skeleton and joints while omitting details about muscles and tendons. Therefore, it differs significantly from the complex musculoskeletal models, such as those created in Anybody [19] or Matlab-based BoB Biomechanics software [29], which take into account elements like tissue elasticity and accurate body segment forms. However, the computational demands of these models limit their usability in real-time scenarios or applications, requiring a large amount of processing power and specialist knowledge for simulation and configuration. The developed model follows certain ideas and solutions from the Hanavan model. Both models assume full symmetry of the body segments, which are connected by spherical zero-mass joints. The segments are treated as single rigid bodies with simple shapes and uniform density.