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Growth hormone secretion in acid-base alterations at rest and during exercise
Clinical Science and Molecular Medicine
|April 1, 1976
Summary
Exercise stimulates human growth hormone (HGH) secretion, independent of blood acidity or lactate levels. Higher exercise intensity correlates with greater HGH release, with sodium bicarbonate influencing peak levels.
Area of Science:
- Exercise Physiology
- Endocrinology
- Biochemistry
Background:
- Exercise elicits significant physiological changes, including alterations in acid-base balance and substrate metabolism.
- Human growth hormone (HGH) secretion is known to be influenced by various physiological stressors, including exercise.
- The specific roles of blood hydrogen ion ([H+]) concentration and lactate levels in exercise-induced HGH release remain incompletely understood.
Purpose of the Study:
- To investigate the impact of altered acid-base balance and lactate concentrations on exercise-induced human growth hormone (HGH) secretion.
- To determine whether changes in blood [H+] and lactate levels mediate or modulate HGH release during varying exercise intensities.
Main Methods:
- Seven healthy males underwent cycle ergometer exercise at 33%, 66%, and 90% of VO2 max.
- Participants received either ammonium chloride (NH4Cl), sodium bicarbonate (NaHCO3), or calcium carbonate (CaCO3) in a double-blind, randomized manner.
- Plasma HGH, lactic acid, and [H+] were measured at rest, during exercise, and during recovery.
Main Results:
- Ammonium chloride administration resulted in higher blood [H+], while sodium bicarbonate led to lower [H+], effects sustained throughout exercise and recovery.
- Plasma lactate concentrations were highest with sodium bicarbonate and lowest with ammonium chloride at 66% and 90% VO2 max.
- Exercise consistently stimulated HGH secretion, with peak levels at 90% VO2 max. being highest following sodium bicarbonate administration.
Conclusions:
- Exercise is a potent physiological stimulus for HGH secretion, with the magnitude of release proportional to exercise intensity.
- The observed exercise-induced HGH secretion mechanism appears to be independent of significant changes in blood [H+] and lactate concentrations.
- While altered acid-base balance and lactate levels do not appear to mediate HGH release, specific conditions like high lactate may influence peak HGH concentrations at maximal exercise.