High-intensity dynamic human muscle performance enhanced by a metabolic intervention

Purpose: The purpose of this study was to quantify the effects of a metabol ic treatment on human muscle dynamic performance (strength, work, and fatig ue) measured under conditions of acute, exhaustive high-intensity anaerobic isokinetic exercise. Methods: Unilateral prefatigue and postfatigue peak t orque and work values were measured in the quadriceps femoris of 13 subject s using a computer-controlled isokinetic dynamometer, over a 23-d interval. The two experimental treatments were: 1) a glycine and L-arginine salt of alpha -ketoisocaproic acid calcium ("GAKIC"); and 2) isocaloric sucrose (co ntrol). Based on a randomized double-blind cross-over repeated measures des ign, measurements were made before and during an exhaustive anaerobic fatig ue protocol to calculate a Fatigue Resistance Index (FRI = [peri-exhaustion torque] + [baseline peak torque]), as well as total work. Results: The FRI and total work for each of the exhaustion sets measured at 0, 5, and 15 mi n after oral GAKIC treatment were greater than values obtained for isocalor ic control treatment (P <0.02). GAKIC treatment increased the mean resistan ce to fatigue (FRI) up to 28% over isocaloric control. Overall gain in tota l muscle work attributable to GAKIC was 10.5 +/- 0.8% greater than control, sustained for at least 15 min. After 24 h, both GAKIC and control concentr ic forces returned to the same absolute values (P > 0.05): mean FRI = 0.42 +/- 0.05 and mean total work = 4600 +/- 280 J. There were no significant di fferences attributable to random order of testing. Conclusions: Compared wi th isocaloric carbohydrate, oral GAKIC treatment increased muscle torque an d work sustained during intense acute anaerobic dynamic exercise; additiona lly, it increased overall muscle performance by delaying muscle fatigue dur ing the early phases of anaerobic dynamic exercise.