The Principles of Exercise Therapy The guiding principle has been to maintain as much of the original text as is compatible with modern practice. It contains a wealth of basic knowledge and the bibliography which points the student to the sources of more advanced knowledge. New and widely varying techniques are constantly being developed and no one of these can claim to be suitable for all patients or all physiotherapists. A sound knowledge of basic principles, an open mind and a spirit of enquiry are essential to progress and the discovery of the methods most suitable to achieve results.