Effects of blood pressure on force production in cat and human muscle

on force production in cat and human muscle. J, Appl. Physiol. 63(2): 834-839, 1987.-In anesthetized cats reducing local ar-terial pressure from 125 to 75 Torr decreased blood flow (53 t 5%) and force production (57 * 7%) in soleus and medial gastrocnemius. Force was produced in these muscles by aerobic, slowly fatiguing fibers. Similar reductions in arterial pressure did not affect force production in caudofemoralis, which con-tains mainly fast-fatiguing fibers. In human subjects the elec-tromyogram produced by the ankle extensors during rhythmic constant-force contractions increased as the contracting mus-cles were raised above the heart during legs-up tilt. This sug-gests that force production of active muscle fibers at a given level of activation fell with muscle perfusion pressure, thus requiring augmentation of muscle activity to sustain the stand-ard contractions. Because aerobic fibers contributed to thes