Force-Velocity and Series Elastic Characteristics of Smooth Muscle from the Hog Carotid Artery

The force-velocity and series elastic characteristics of vascular strips from the media of hog carotid arteries were determined using the method of quick release to a known afterload. Shortening velocity was a function of load, and the data could be fitted by a rectangular hyperbola using the Hill equation, (P + a) V = b (Po − P), where P is the load, Po is the maximum isometric force developed at the optimum muscle length (Lo), V is velocity, and a and b are constants. The following dynamic constants were obtained for the electrically stimulated strips: estimated maximum shortening velocity for the unloaded muscle (Vmax) = 0.12 Lo/sec, b = 0.02 Lo/sec, Po = 1.80 kg-wt/cm2 = 1.76 × 106 dynes/cm2, and a/Po = 0.18. Maximum power output occurred at a load of 0.28 Po. The stress-strain curve for the series elastic component could be approximated by the simple exponential equation, stress = 0.034e058 strain. The extension of the series elastic component at Po was 7.2% of Lo.