Critical to the evaluation of potential therapeutics (pharmacological, gene or cell therapies) in mouse models of muscular dystrophy are sensitive and repeatable physiological assessments of muscle function. Therefore, we are proposing to create a research core which performs ex vivo, in situ, and whole animal assessments of muscle integrity and function. Three of the projects (Projects 1-3) proposed in this grant contain components that require muscle physiological measurements. (Project 4 relies on the outcome of these tests for pre-clinical justification.) The Physiological Assessment Core will meet the needs of the projects within this grant, as well as the needs of the muscular dystrophy research community. In addition, the core will maintain in house colonies of mouse models of DMD, LGMD, and myotonic dystrophy in order to support studies where long-term testing is necessary. The resources of this core are contained within Dr. Sweeney's laboratory, which includes all instrumentation for muscle physiological measurements, as well as specialized equipment for hindlimb suspension experiments, documented free wheel running, and treadmill running. Dr. Barton is a muscle physiologist with extensive experience evaluating muscle function in mice. Monica Zadel is an expert at performing muscle mechanical experiments, while Pedro Acosta maintains our breeding colonies and will monitor hindlimb suspension and free wheel running experiments. We believe that this Core will provide a valuable resource that will enable the entire muscular dystrophy research community to utilize these assays to assess the potential benefits of a large number of approaches to the treatment of different forms of muscular dystrophy