The calculation of the possible load on human joints is of great importance in orthopedics. The magnitude of the force transmitted in the joints during the process of movement, whether in everyday life or in athletics, plays a decisive role. Especially at moments of impact, as in sports, high accelerations are transmitted through the human body. Bones and tissue (muscles, tendons and ligaments) react quite differently in this phase, and their reactions have a large influence on the magnitude and course of the forces working within the body, particularly in the joints. In previously developed methods of load-determination on joints during dynamic movements, these reactions were not considered. In the following paper, however, we will introduce a physical model that takes the various materials of the body's constitution into account. By introducing "wobbling mass", which, elastically damped, is coupled to the bony parts of the body, we can simulate the reaction of the body tissues, and a realistic calculation of the forces and moments transported through the body can be reached. The temporal sequence of these magnitudes for the knee and hip joints will be illustrated using an exemplary selected movement and interpreted using simplified joint structures. The main features of the method of calculation, using simple examples from statics, will be shown in Part One of this paper.