The idea of assessment in the fields of physical exercise and health refers to a process of attributing values or concepts. This attribution is certainly key for the prescription of physical exercise but it is not its most important role. This book presents and discusses research which shows physical exercise and health professionals the importance of a program of measurement and assessment which enables to safely prescribe physical exercise to elderly people, since this prescription must be supported by a scientific basis in order to be considered a credible and responsible piece of work.