ABSTRACT In this article, Pedro Prado, PhD, brings to the fore the importance of the autonomic nervous system (ANS) for Rolfing theory and practice. The psychobiologic perspective of the work expands its assessment tools by making use of the work of Peter Levine, PhD (Somatic Experiencing®) and Stephen Porges, PhD (polyvagal theory). Prado presents these theories and makes correlations that can be useful for the practical application of SI.