Acute metabolic, hormonal, and psychological responses to different endurance training protocols

In the last years, mainly 2 high-intensity-training (HIT) protocols became common: first, a Wingate-based "all-out" protocol and second, a 4×4 min protocol. However, no direct comparison between these protocols exists, and also a comparison with high-volume-training (HVT) is missing. Therefore, the aim of the present study was to compare these 3 endurance training protocols on metabolic, hormonal, and psychological responses. Twelve subjects performed: 1) HVT [130 min at 55% peak power output (PPO)]; 2) 4×4 min at 95% PPO; 3) 4×30 s all-out. Human growth hormone (hGH), testosterone, and cortisol were determined before (pre) and 0', 30', 60', 180' after each intervention. Metabolic stimuli and perturbations were characterized by lactate, blood gas (pH, BE, HCO₃⁻, pO₂, PCO₂), and spirometric analysis. Furthermore, changes of the person's perceived physical state were determined. The 4×30 s training caused the highest increases in cortisol and hGH, followed by 4 × 4 min and HVT. Testosterone levels were significantly increased by all 3 exercise protocols. Metabolic stress was highest during and after 4×30 s, followed by 4×4 min and HVT. The 4×30 s training was also the most demanding intervention from an athlete's point of view. In conclusion, the results suggest that 4×30 s and 4×4 min promote anabolic processes more than HVT, due to higher increases of hGH, testosterone, and the T/C ratio. It can be speculated that the acute hormonal increase and the metabolic perturbations might play a positive role in optimizing training adaptation and in eliciting health benefits as it has been shown by previous long term training studies using similar exercise protocols.