Phi in physiology, psychology and biomechanics: The golden ratio between myth and science

In recent years, there has been a renewed interest in the use of the so-called golden ratio (Phi, ϕ), an irrational number with fractal properties, used in artworks since V century BC. and now for modelling complex biological structures and functions. This number, in fact, recursively pops-up in human history, from Ancient Greeks to Renaissance, and to contemporary scientific studies. Nevertheless, recent scientific results often fall between two extremes: those of a priori sceptic researchers accusing the artificial emergence of ϕ in many studies, and those of researchers that find a mystic meaning in the presence of ϕ in human physiology. This review moves between these two extremes to provide a scientifically based discussion about the possible presence of Phi in human physiology, psychology, and biomechanics of heart and locomotion. We provide scientific evidence, analysing reasons for the presence of Phi, reporting the weakness of some studies overstating the potential meaning of this number, and reporting the reasons for which it could be actually found in some biological structures and functions.