It’s no secret, the positive anti-aging effects Human growth hormone and insulin-like growth factor-1 has on the body including increased fat metabolism, increased muscle mass, increased bone density, collagen rejuvenation, and more. Although the exact mechanisms that are most efficacious for stimulating release of these anti-aging hormones remains some-what of a mystery, scientists are getting closer.

Evidence suggests that load and frequency are determining factors in the regulation of hGH secretion. Despite the significant exercise-induced growth hormone response (EIGR) induced by resistance training, much of the stimulus for protein synthesis has been attributed to insulin-like growth factor-1 with modest contributions from the hGH-GH receptor interaction on the cell membrane. The EIGR to endurance exercise is associated with the intensity, duration, frequency and mode of endurance exercise. A number of studies have suggested an intensity ‘threshold’ exists for EIGR. An exercise intensity above lactate threshold and for a minimum of 10 minutes appears to elicit the greatest stimulus to the secretion of hGH. Exercise training above the lactate threshold may amplify the pulsatile release of hGH at rest, increasing 24-hour hGH secretion. The impact of chronic exercise training on the EIGR remains equivocal. Recent evidence suggests that endurance training results in decreased resting hGH and a blunted EIGR, which may be linked to an increased tissue sensitivity to hGH.
Sports Med. 2003;33(8):599-613.