Exercise induced endogenous hormone levels have been studied extensively. Researchers have examined how the different components of training including sets, repetitions, load and rest intervals affect serum levels of hormones such as testosterone, growth hormone and cortisol. Many studies have demonstrated there is an acute increase in serum levels of anabolic hormones after intense resistance exercise.

To be more specific, high intensity exercise coupled with short rest intervals that is performed with large muscle groups are associated with large rises in these hormones when compared to other training methods. Conversely, training small muscle groups like the biceps has been shown to have no effect on serum hormone levels. Because of the findings in many studies, training programs have been constructed to maximize the post-exercise rise in these hormones based on the assertion that exercise-induced increases in hormones like testosterone and GH will enhance muscle size and strength. But, considering the fact that these increases in hormone levels are very small and of short duration, will they produce muscular gains.

A study from the Kinesiology Dept. of McMaster University in Canada found that exercise induced hormone levels had no effect on muscle size or strength after 15 weeks of resistance training.

There is evidence that a minimal basal level of testosterone is required to support strength and hypertrophy gains, which are otherwise attenuated. Therefore, the hormone-sensitive processes that underpin muscle anabolism at hypo- and supra-physiological hormone levels are not being activated appreciably by exercise-induced increases in hormone availability or at least do not result in any measurable enhancement of strength or hypertrophy.

(J Appl Physiol 108(1); 2010)

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.