9514383 Rome It has been empirically shown that small animals (e.g. mice and rats) move their limbs at higher frequencies than large animals (man or horses) and that it costs more energy per gram for a small animal to move a given distance than for a large one. In this proposal, the principal investigator (PI) will ask "how is the muscular system designed to permit much faster movements in small animals and why does it cost much more energy for small animals to run than large ones?" It has been hypothesized that the difference lies in the properties of the muscle fibers. The muscle fibers of the small animals are thought to be much faster--a necessity for the high frequencies at which these animals run. But there is a price: very fast muscle fibers use far more energy to generate force, thus potentially explaining why it is more costly for small animals to run. The PI will test the above hypothesis by measuring how speed and the energetic cost of generating force of different fiber types scales with body size in animals ranging from rats to horses. The long-term goal of the PI's research is to understand the design of muscular systems. This involves performing specific experiments that facilitate the integration of information from molecular, cellular and whole animal studies. This approach is crucial because there are large gaps in our knowledge of the principles by which animals use their muscles. Further, elucidation of the principles of how healthy motor systems work may have far-reaching application in terms of health and athletic performance of humans and other animals. For instance, the information obtained from these studies may be useful in 1) understanding disease/injuries of the motor/cardiovascular systems; 2) designing computer systems for aiding movement in the handicapped; 3) designing pharmacological and genetic interventions for muscle disease states; 4) understanding the functional basis of training/rehabilitation; and 5) choosing appropriate skeletal muscle fo r heart pumping assist. With recent attempts to use tissue from non-human species in man, these studies would be particularly important as they will provide a data base of muscle speeds from which physicians might be able to choose a good match for a particular function in humans. This information will also be important for veterinary medicine. ***
