Maximal blood flow and power output of dog muscle in situ

The two goals of this study were: 1) to establish a stimulation pattern which would drive the gastrocnemius-plantaris muscle of the dog, in situ, to maximal work rate, W, and 2) to determine whether the surgical isolation of the circulation of this muscle, necessary to measure the muscle flow, Q, reduced the muscle's performance. The first goal was achieved in a preparation with minimal surgery, MS, to isolate the nerve and the tendon. The nerve was cut and connected to a stimulator, and the tendon was cut and connected to a pneumatic lever system. Wmax during 1.s-1 contractions occurred with a load of 270 g.g-1 and 200-ms trains of impulses at a frequency of 60.s-1. At 50 imp.s-1, the accepted maximal frequency which would occur in vivo, the Wmax which was maintained for 4 min was 19 mW.g-1. The second goal was met in a second series of experiments in which the venous circulation was isolated, FS. During a 20-min series of 30-s work periods with 2 min rest each, maximal W was 11.9 mW.g-1 at 50 imp.s-1. Following a 10-min additional rest, the muscle was stimulated for 10 min. The W, Q, and VO2 at 2-4 min were 10.0 mW.g-1, 1.73 ml.g-1.min-1 and 194 microliters.g-1.min-1, respectively. Q and VO2 were linearly related to W. Assuming a linear extrapolation, the FS early maximum in the brief tests as W = 11.9 mW.g-1, Q would be 2.06 ml.g-1.min-1 and VO2 would be 231 microliters.g-1.min-1.(ABSTRACT TRUNCATED AT 250 WORDS)