BackgroundSkeletal muscle can be used for cardiac assistance after electrical stimulation over a period of several weeks. This will adapt it to do chronic work with no resulting fatigue. The result of this procedure, however, is a reduction of 80% in muscle power, >60% in muscle mass, and;≈ 85% in contractile speed. To minimize these disadvantages, the following study was done to develop and test a method to dynamically train skeletal muscle ventricles (SMVs).Methods and ResultsBarrel-shaped SMVs were tested in 15 Jersey calves. They were made from the latissimus dorsi muscle, which was wrapped around an elastic silicone training device. Six SMVs were used extrathoracically in a single layer and nine intrathoracically in a double layer. With dynamic training preserving contractile speed, the output increased to ≈5 L/min, the systolic pressure increased to >200 mm Hg, and power developed to ≈10 W after 3 months of dynamic training. The contractile speed of dynamically trained SMVs was between 250 and 700 mm/s. The diameter of the latissimus dorsi muscle increased to three times that of the corresponding contralateral muscle.ConclusionsThe combination of electrical conditioning with dynamic training of the SMVs resulted in a strong muscle pump that did not develop fatigue. Dynamic training for skeletal muscle represents a new and promising method for providing powerful autologous cardiac assist.