Abstract

At the onset of a rectangular electric stimulation and/or exercise, anaerobic glycolysis sets in with a variable time delay that depends on work intensity and temperature. The adjustment of muscular blood flow (MBF) upon a square wave of exercise is very fast both in the isolated dog gastrocnemius (t 1/2 = 9 s) and in human muscles (t 1/2 = 5 to 10 s). Training increases considerably the speed of adjustment. At work onset, O2 consumption is rate limited by a single first order reaction the kinetics of which, as determined by the half time of the VO2 on response (t 1/2 VO2 on) is approximately 17 s both for isolated dog gastrocnemii stimulated with trains of short tetani and for intact running dogs. The t 1/2 VO2 on varies in man (18 to 90 s) accompanied by a variable transient early lactate accumulation related to the variable depletion of body oxygen stores. t 1/2 VO2 on is shortest (18 s) for trained muscles that are also characterized by lower early lactate release. t 1/2 VO2 on of muscles with artificially depleted PC and O2 stores is 12 to 26 s and reflects the true kinetics of mobilization of oxidative energy. Defects of various steps along the glycolytic pathway can be assessed by measurement of t 1/2 VO2 on and early lactate. Verf.-Referat