It is over 25 years since isokinetic dynamometry was first introduced into clinical practice and exercise science. Physical therapy, in particular, has benefited significantly from this technology, which rapidly became the tool of choice in hundreds of research papers as well as the cornerstone of quantitative muscle performance assessment in the clinical setting. About 1984, the technology behind isokinetic dynamometry made considerable progress when computers were incorporated to control the hardware, that is the integral power sources and the on-line processing of mechanical signals. This enabled users to establish a common basis for carrying out eccentric contractions and to obtain comprehensive information on muscle strength immediately. This book does not pretend to cover all the topics that have been examined under isokinetics. Nor is it intended to be a quick and superficial introduction to clinical applications. Rather, it is aimed at those who have at least some experience and are at a stage where they are beginning to ask some very serious questions and would not necessarily be happy with very simple answers. This book attempts to draw an unbiased picture of isokinetics. The source material used throughout the book is based exclusively on papers which appeared in peer review journals. Published abstracts are referred to in only a few cases. The first four chapters cover relevant biomechanical and physiological issues, aspects of operation, measurement, validity and reproducibility, and isokinetically-based muscle conditioning methods. The other five chapters describe the use of isokinetics on the major joint systems of the body: the hip, knee, ankle, spine and shoulder. The elbow and wrist joints are not dealt with in separate chapters as the database is insufficiently comprehensive. The section on the medicolegal applications of isokinetics is not based exclusively on published material.