Jacobson, B. H. (1990). Effect of amino acid on growth hormone release. The Physician and Sportsmedicine, 18, 63-69.

This review analyzed the effect of amino acid supplementation on the rate of human growth hormone release.

"Current anecdotal information from the athletic, weight lifting, and bodybuilding communities is that dietary supplementation with amino acids will result in increased muscle mass (hypertrophy), strength, and endurance, and will reduce recovery time." (p. 63)

1. Some evidence suggests that human growth hormone (hGH) is linked to muscle hypertrophy and its secretion is known to increase with exercise. Exercising athletes require a greater daily intake of protein than sedentary individuals. Some amino acids, specifically the branched-chain amino acids (BCAA), are oxidized not only by the liver but by active skeletal muscles as well. (p. 64)
2. The mechanism for exercise-induced hGH release has not been fully defined, but it has been suggested that resistance weight training within a specific percentage of an individual's maximum limit may promote hGH response. The magnitude of hGH release is not only guided by exercise intensity and duration, but also by fitness level and type of exercise, with intermittent exercise resulting in greater secretion than continuous exercise. "Endurance exercise elicits a greater elevation in serum growth hormone than does strength training." (p. 64)
3. No contemporary evidence supports the notion that amino acid supplementation combined with strength training augments muscle hypertrophy or functional strength over that which could be obtained by strength training alone.
4. Work and hormone-induced muscle growth have been determined to be the result of two independent biochemical processes. Both produce increase in muscle mass (hypertrophy) but only exercise-induced growth stimulates the contractile properties of muscle. Hormone-induced growth does not produce such stimulation and thus, strength does not increase. Hypertrophy in the hormone-induced growth condition only occurs because of increase in noncontractile protein. Few realize the difference in effects of these two processes.
5. HGH-induced growth mimics many anomalous growth diseases (e.g., acromegaly) which result in unusual size but with no corresponding increase in performance.

Implication. Artificially induced hGH increases are likely to result in increased physical size but without an accompanying performance benefit. Only when exercise stimulates increased hGH secretion do performance-benefiting changes occur. The introduction of hGH or catalysts that produce excessive hGH secretion should not be considered to be ergogenic aids in light of current knowledge. Indiscriminate use and stimulation of hGH could lead to growth-related diseases.

"When exercise stimulates increased hGH secretion, some of that increase is used in a performance-enhancing manner. However, when hGH is elevated artificially, although size increases, there is no accompanying performance benefit. Apparently, a training stimulus is required to produce a specific sporting improvement." So what is new?

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