THE RELATIONSHIP OF GROWTH HORMONE TO ISOKINETIC EXERCISE: CONCENTRIC VS. ECCENTRIC.

Abstract

1089 The goal of this study was to compare the hormonal response of concentric and eccentric leg extension to determine which mode of exercise provides the greatest stimulus. Nine healthy untrained male subjects preformed a concentric (CON) trial at 75% of a CON IRM using sets of 10 repetition until they were unable to maintain the workload. Eccentric (ECC) trials (75% of an ECC 1 RM) using the same protocol and total work were performed one week later. An integrated EMG (IEMG) of the rectus femoris and vastus lateralis muscles were recorded on the active leg during each exercise trial. Blood samples were drawn before and at post-exercise and analyzed for growth hormone (hGH), creatine kinase (CK), and lactic acid (Lct). The results from this study indicate that the CON trial produced a significantly higher post-exercise hGH response than the ECC trial. The peak hGH for the CON was 8.32 ± 3.21, while the peak for the ECC was 3.8 ± 1.2. The CON trial produced a 21/2 fold higher Lct response than the ECC trial. Muscle soreness was ranked higher in the ECC trial but the CK response suggests that the CON exercise was more damaging. The IEMG data indicates that electrical activity was similar for the two forms of exercise. The results from this study suggest that muscle damage is a more important stimulant for hGH release that the form of exercise. (Funded by Korean Association of Samuel Research)