Aim: The purpose of the present study was to compare the acute hormonal response to a short term high intensity training (HIT) versus a high volume endurance training (HVT) and to determine the contribution of the metabolic acidosis as a stimulus for possibly different reactions of circulating hGH, IGF-1 and IGFBP-3 levels. Methods: Eleven subjects participated in three experimental trials. Two times subjects performed four 30 s "all-out" exercise bouts on a cycle ergometer adjusted to an isokinetic mode separated by 5 min rest each (whereas subjects either received NaHCO3 (HIT(B)) or a placebo (HIT(P)) before the exercise). The third exercise trail consisted of a constant load exercise for 1 h at 45 % VO2max (HVT). Venous blood samples were taken under resting conditions, 0h, 1h and 4h after each exercise condition to determine hGH, IGF-1 and IGFBP-3 serum concentrations. Capillary blood samples were taken during and after the interventions to determine lactate concentrations and blood gas parameters. Results: Power output, mean lactate concentrations and mean pH values were significantly higher during HIT(B) compared to HIT(P). Blood gas parameters showed no major changes during HVT. Serum hGH concentration was significantly increased 10 min post-exercise in both HIT interventions, IGFBP-3 levels only after HIT (P). IGF-1 showed no reactions to HIT. HVT showed no effects on hGH, IGFBP-3 and IGF-1 levels. Additionally it could be shown that alterations in the acid base status influence the hGH and IFGBP-3 response to exercise. The diminished acidosis during HIT(B) attenuates the hGH and IGFBP-3 response. Conclusion: These data indicate that an increase in blood hydrogen ion concentration may be partly responsible for the hGH and IGFBP-3 response to acute high-intensity anaerobic exercise. This could be beneficial to individuals who can exercise longer and at a higher intensity in intervals than would be possible using a continuous protocol.