Book excerpt: Rider Biomechanics is a collaboration between rider biomechanics coach Mary Wanless and functional anatomist Thomas Myers. Myer's seminal book Anatomy Trains explains how connective tissue joins muscles together into functional chains. Some of these chains extend from head to toe, and they are the 'lines of pull'. Elite riders excel in balancing the tension in their lines, creating a stable balanced structure which can transmit and redirect the forces of the horse's movement. Easy, fluid, sitting eludes less skilled riders - but this book, with its copious photographs and illustrations, provides a route map for reorganising 'lines of pull', sitting, and influence on one's horse. It is through balancing one's own lines that you learn how to balance one's horse, changing his carriage and movement, and discovering the secrets of the few talented riders who naturally possess those skills.