Endogenous Hormonal and Growth Factor Responses to Heavy Resistance Exercise Protocols

To examine endogenous anabolic hormone and growth factor responses to various heavy resistance exercise protocols (HREPs), nine male subjects performed each of six randomly assigned HREPs which consisted of identically ordered exercises carefully designed to control for load (5RM vs 10RM), rest period length (1 min vs 3 min) and total work (J) effects. Serum human growth hormone (hGH), tesosterone (T), somatomedin-C (SM-C), serum glucose and whole blood lactate (HLa) concentrations were determined pre-exercise, mid-exercise and at 0, 5, 15, 20, 60, 90, and 120 min post-exercise. All HREPs produced significant increases in serum T concentrations although the magnitude and frequency above resting values varied across HREPs. The highest hGH concentrations were observed consequent to high total work, 1 min rest periods and 10RM load. All HREPs did not produce increases in serum hGH. The pattern of SM-C increases varied among HREPs and did not follow hGH changes. These data suggest that the release patterns and the magnitude of increases are functions of the type of HREPs utilized. Thus, all HREPs may not effect muscle and connective tissue growth in the same manner due to differences in hormonal and growth factor responses. Keywords: HUman growth hormone, Somatomedins, Insulin- like growth factors, Testosterone, Resistance exercise, Lactate, Males.