The overall objective of the research program is to develop an implantable artificial muscle which will function similarly to the natural muscle being replaced. To accomplish this objective, various rubbers and plastics are fabricated into artificial muscle systems (muscle bellys and tendons) and then implanted in the sheep. Various modes of attachment, i.e., natural tendon to artificial tendon, bone to articificial tendon, etc., will be investigated. Strain gages are incorporated in the muscle belly and provide a unique tool for gathering fatigue information on the elastic muscle belly during chronic implantation. The artificial muscle system is used to replace the muscle bundle and common tendon of the peroneus tertius, extensor digitorium longus, and extensor digiti tertii proprius in the sheep. Different preloads on the artificial muscle system are used in each experiment to determine which provides the most normal walking pattern in the sheep.