These lecture notes were prepared in order to help psychologists participating in the course gain a closer understanding of several key processes which occur in the world of sports, so that they can get a more complete picture of the psychological processes involved. Since psychologists have considerable previous experience of biology, we will not go through the knowledge acquired during the semesters dealing with studies on cell biology, anatomy and physiology again, but we assume a background knowledge of these fields. Naturally, this does not mean that it is expected that students know everything they studied during the biology subjects; however, from time to time it is advisable to look back and go over them again when the need arises. Over the course of the subject, we attempt to understand what the conditions of the mechanical and dynamic loadability of the locomotor system are, and why and how one goes beyond its limits during sporting activity. This leads to the complex topic of injuries, in which we become acquainted with the more detailed structure of the joints and their injury types, as well as with the fundamental characteristics of the methods used to treat them. Understanding the biological side of injuries is important because it enables us to better comprehend the psychological processes provoked by these frequently occurring events, and to allow us to provide more effective sports psychological assistance to both athletes and coaches. Those parts of the text appearing in small case do not form part of the compulsory material, but it is advisable to know them, because to achieve a high level of cooperation with sports medical doctors it is desirable for a professional psychologist to also understand the technical language used to describe sports injuries. This encourages efficient communication, and with the help of our increased competence we will be able to effectively fit our support work to the complex processes which lie behind sports performance.