# Development of a Simplified Human Body Model for Movement Simulations
## 3 Results  
The numerical model in Adams moved according to the implemented motions based on the biomechanical angles calculated using the software of the IMU system's manufacturer. The progress of the simulation can be observed in Figure 5a-d, where the sequence of movements is presented. According to the assumptions and observations, at the end of the simulation, the model's lower limbs, trunk, and head almost returned to the initial position (straight position), while the upper limbs changed their orientation and final positions due to the box being held in front of the person. The entire experiment, which lasted for about 14 s, was reproduced in Adams, starting with nearly a 10 s preparation and calibration in the T-stance (as visible in Figure 4a). For this reason, the first 9 s were omitted in the graphs, and the analysis of the results focused on the actual studied movement--in the range of 9.5 s to 14 s. Moreover, only some of the obtained results, focusing mainly on the upper and lower limbs, are presented in the plots (Figures 6-12), with the most important outcomes summarized as numerical values. The following plots present, for each particular joint, the angular displacement or moment of force as three waveforms for the joint movement, where F/E stands for flexion/extension, A/A stands for abduction/adduction, and Rot stands for internal/external rotation. As previously mentioned, the presented results follow ISB standards for human motion. Joint angles are measured using coordinate systems based on defined anatomical planes (sagittal, frontal, and transverse) and axes, as well as by applying the right-hand rule for the definition of coordinate systems. For the hip joints, the F/E movements achieve similar waveform shapes and values for the left and right limbs, with min. and max. values of \(-\)5.84\({}^{\circ}\) and 93.90\({}^{\circ}\) for the left side (Figure 6a); and \(-\)3.84\({}^{\circ}\) and 93.86\({}^{\circ}\) for the right side (Figure 6b). The A/A and Rot achieved minor values when compared to the main motion F/E. In the case of the knee joint (Figure 7a), a large increase in the F/E angle from about 10 s to 13 s was observed. It corresponds to the tested movement of lifting an object from the ground. A negative value at the end of the simulation indicates a small hyperextension of the knee. The minimum and maximum values of the achieved angle were 0.06\({}^{\circ}\) and 51.62\({}^{\circ}\) for F/E at the left joint, \(-\)1.69\({}^{\circ}\) and 54.29\({}^{\circ}\) at the right joint, \(-\)2.20 \({}^{\circ}\)and 0.46\({}^{\circ}\) for A/A at the left knee, and \(-\)8.04\({}^{\circ}\) and 1.48\({}^{\circ}\) at the right knee, respectively. For the ankle joint, the maximum and minimum achieved values were: F/E at the left ankle \(-\)7.17\({}^{\circ}\) and  
Figure 5: Sequence of pictures presenting the simulated movement with the indicated time: (**a**) bending forward (10.5 s); (**b**) full bending down and gripping the box (11.52 s); (**c**) straightening up and lifting the box (12.54 s); and (**d**) final position with the box kept in the hands (14.0 s). In the case of the shoulders, both graphs are similar to each other for all three movements in terms of the characteristics of the waveforms and the achieved values of the angle. The largest change in the angle can be observed for the A/A movement, where the extreme values are \(-8.91\)d\({}^{\circ}\) and \(93.39^{\circ}\) for the left side and \(-7.54^{\circ}\) and \(84.94^{\circ}\) for the right side. The results correspond to the simulated movements of a person grabbing an object and straightening up while still holding the arms straight in the front. The minimums and maximums obtained were \(-5.02^{\circ}\) and \(44.66^{\circ}\) at the left shoulder for F/E, and \(-17.28^{\circ}\) and \(35.64^{\circ}\) at the right shoulder. An important fact is that in the case of shoulder joints, corrections were applied to the F/E and A/A movements obtained from the IMU sensor system.