EXPERIMENTAL IN-SITU CONDITIONING OF THE LATISSIMUS-DORSI MUSCLE FOR CIRCULATORY ASSIST BY MULTICHANNEL STIMULATION

This study was undertaken to survey the changes in force and fatigue o f the latissimus dorsi muscle during transformation into a fatigue-res istant muscle by indirect or nervous multichannel stimulation. In shee p, a silicone chamber connected to a pressure-transducing system was i mplanted under the left latissimus dorsi muscle. Muscle conditioning w as performed by multichannel (carousel) stimulation of the thoracodors al nerve. The program was started with active periods of 10 min/h prod ucing 10 tetanic contractions/min. It was increased until 70 contracti ons/min could be performed during 24 h. The changes of muscle force an d fatigue were monitored by the silicone balloon system. After a mean period of 22 weeks, fatigue resistance was reached. The fatigue-resist ant muscle was able to produce a pressure of about 100 mm Hg in the ba lloon. After finishing the conditioning procedure, muscle forces and t he fatigue resistance of the conditioned muscle were evaluated. The co nditioned muscle showed only a minimal decrease of force during 20 min . Under a preload of 20 N, it exhibited a maximum tetanic tension of 9 5 N.