Exercise training decreases the growth hormone (GH) response to acute constant-load exercise

Area of Science:

• Exercise Physiology
• Endocrinology
• Sports Science

Background:

• The growth hormone (GH) response to exercise is influenced by training status.
• Understanding how training adaptations affect acute exercise hormonal responses is crucial for optimizing training protocols.

Purpose of the Study:

• To investigate the impact of short-term exercise training on the GH and catecholamine response to a standardized high-intensity exercise bout.
• To determine if adaptations occur within the first 6 weeks of training.

Main Methods:

• Six untrained males underwent a 20-minute high-intensity, constant-load exercise test before and after 3 and 6 weeks of training.
• Measurements included oxygen uptake (VO2), lactate threshold (LT), and integrated GH, plasma epinephrine, and norepinephrine concentrations.
• Absolute power output was kept constant across all tests.

Main Results:

• Training improved VO2 at lactate threshold, VO2 at 2.5 mM blood lactate, VO2peak, and power output at lactate threshold.
• Integrated GH concentration during exercise and recovery was significantly lower after 3 and 6 weeks of training compared to pre-training.
• Plasma epinephrine and norepinephrine responses also showed a significant reduction post-training, mirroring the GH response.

Conclusions:

• Exercise training, even within 3 weeks, attenuates the GH and catecholamine response to a constant-load exercise stimulus.
• These findings support the hypothesis that a specific exercise intensity threshold is required to elicit a significant GH release.