Sports science is a discipline that studies how the healthy human body works during exercise, and how sport and physical activity promote health and performance from cellular to whole body perspectives. The study of sports science traditionally incorporates areas of physiology (exercise physiology), psychology (sport psychology), anatomy, biomechanics (sports biomechanics), biochemistry, and kinesiology. Sports scientists and performance consultants are growing in demand and employment numbers, with the ever-increasing focus within the sporting world on achieving the best results possible. Through the scientific study of sports, researchers have developed a greater understanding of how the human body reacts to exercise, training, different environments, and many other stimuli. Origins of exercise physiology Sports science can trace its origins to ancient Greece. The noted ancient Greek physician Galen (131–201) wrote 87 detailed essays about improving health (proper nutrition), aerobic fitness, and strengthening muscles. New ideas upon the working and functioning of the human body emerged during the Renaissance as anatomists and physicians challenged the previously known theories. These spread with the implementation of the printed word, the result of Gutenberg's printing press in the 15th century. Allied with this was a large increase in academia in general, universities were forming all around the world. Importantly these new scholars went beyond the simplistic notions of the early Greek physicians, and shed light upon the complexities of the circulatory, and digestive systems. Furthermore, by the middle of the 19th century, early medical schools (such as the Harvard Medical School, formed 1782) began appearing in the United States, whose graduates went on to assume positions of importance in academia and allied medical research. Medical journal publications increased significantly in number during this period. In 1898, three articles on physical activity appeared in the first volume of the American Journal of Physiology. Other articles and reviews subsequently appeared in prestigious journals. The German applied physiology publication, Internationale Zeitschrift fur Physiologie einschliesslich Arbeitphysiologie (1929–1940; now known as the European Journal of Applied Physiology and Occupational Physiology), became a significant journal in the field of research. A number of key figures have made significant contributions to the study of sports science: Austin Flint, Jr., (1836–1915) One of the first American pioneer physicians, studied physiological responses to exercise in his influential medical textbooks. Edward Hitchcock, Jr., (1828–1911) Amherst College Professor of Hygiene and Physical Education, devoted his academic career to the scientific study of physical exercise, training and the body.