MECHANICAL-PROPERTIES OF RABBIT LATISSIMUS-DORSI MUSCLE AFTER STRETCHAND OR ELECTRICAL-STIMULATION/

The work loop technique was used to measure the mechanical performance in situ of the latissimus dorsi (LD) muscles of rabbits maintained un der fentanyl anesthesia. After 3 wk of incrementally applied stretch t he LD muscles were 36% heavier, but absolute power output (195 mW/musc le) was not significantly changed relative to that of external control muscle (206 mW). In contrast, continuous 10-Hz electrical stimulation reduced power output per kilogram of muscle >75% after 3 or 6 wk and muscle mass by 32% after 6 wk. When combined, stretch and 10-Hz electr ical stimulation preserved or increased the mass of the treated muscle s but failed to prevent an 80% loss in maximum muscle power. However, this combined treatment increased fatigue resistance to a greater degr ee than electrical stimulation alone. These stretched/stimulated muscl es. therefore, are more suitable for cardiomyoplasty. Nonetheless, fur ther work will be necessary to find an ideal training program for this surgical procedure.