Over 100,000 Americans die yearly of heart failure despite all present treatments. One promising suggested treatment innovation employs multiple skeletal muscles, hydraulically linked to power already-proven mechanical support devices. But the required durable load-bearing muscle-to-prosthetic interface has never succeeded, perhaps because tissue cannot tolerate the pressures generated-ranging to 40,000 mmHg-when necessary forces meet available cross-sectional areas. Dramatically increasing the force-transfer surface, by dispersing ultrafine polymer fibers distally in the muscles, may solve the dilemma, particularly if uninterrupted exiting fibers are integrally organized into a non-extensile cord. That is the MyoCoupler(TM). Effective force-transfer is obtainable with realistic friction coefficients and physiologic tissue pressures. Simple pull-out strength in a pilot 30 day rabbit test was nine times projected need. We will implant devices, and controls (identical cords fixed by buttressed sutures) contralaterally (random side assignment), in the posterior tibial muscle groups of 20 rabbits for 90 days-16 for bond-strength testing; 4 for interface ultrastructure. The hypothesis is that the MyoCoupler(TM) integrates thoroughly with tissue to provide a strong, durable, load-bearing muscle/prosthetic bond adequate for powering circulatory support. Expected findings would strongly support aggressive pursuit of muscle- powered mechanisms for artificial hearts, assist devices, and heart wail actuators. PROPOSED COMMERCIAL APPLICATIONS: The Muscle-to prosthesis coupler could provide circulatory support free of external power. This would reduce the risk and improve quality of life for the majority of those now dying with or disabled by heart failure-a potential market of 50,000 to 100,000 people in the USA alone each year, each utilizing 4 to 6 couplers. The complexity of the device is similar to a heart valve or a joint prosthesis, supporting a unit price of $2,000 to $4,000. This yields a domestic market of $400 million to $2.4 billion annually.