From Charles Poliquin
How important is the hormone response to training? The widely accepted view is that testosterone, growth hormone, and IGF-1 are critical to muscle building, fat loss, and performance. However, a closer look shows that even though there are numerous associations between these hormones and hypertrophy, fat loss, and strength development, contradictions abound.
A new review in the Journal of Strength and Conditioning Research considers the hormone hypothesis that suggests that acute post-workout increases in hormone levels play a primary role in building muscle. Heres what we do know with my take aways:
1) Resistance training can result in a post-workout increase in the anabolic hormones, testosterone, growth hormone, and insulin-like growth factor-1. However controlled studies show contradictory results as to the magnitude of increase and the relation with muscle or strength gains.
Therefore, the question is not whether there is a hormone response to exercisethis is well establishedbut how much it differs based on gender, age, training status, and training program. In addition, the physiological effect of this response and the mechanism via which that effect occurs is what remains unknown.
Take Away: Theres a hormone response to training. Is it relevant to body composition? Probably, but we dont definitively know why or how.
2) Testosterone has an anabolic effect. Suppressing testosterone (T) release in young men who are resistance training leads to less muscle development. The same thing happens to older women with lower testosteronethey build less muscle with resistance training with lack of T.
The muscle-growth related effects of testosterone are believed to occur due to an increase in muscle protein synthesis and a decrease in muscle breakdown. T may also enhance the release of growth hormone (GH) and IGF-1, while decreasing levels of hormones that inhibit IGF-1s action. T has also been shown to increase satellite cell growth, which are dormant cells that can lead to greater hypertrophy when activated.
Testosterone response appears to be very individualized: Some studies show T was elevated to a greater extent following hypertrophy-style training compared with strength-type training, but this is not conclusive.
Take Away: Testosterone has a muscle-building effect and its correlation with performance cant be ignored. Still, much is unknown and further investigation is needed to identify the effect of training variables and T response. Supporting the bodys ability to produce testosterone with lifestyle and dietary behaviors may be most important.
3) Growth hormone is critical for body composition because it has both a muscle building effect and it inhibits muscle breakdown. It acts to enhance fat metabolism and stimulates cellular uptake and the incorporation of amino acids into various proteins, including muscle. Its suggested that GHs primary role in building muscle is via its ability to enhance the action of IGF-1, rather than to control it.
Despite being unappreciated for its hypertrophy effects, GH has been associated with muscle gains in recent studies. In one study of untrained young men there was a weak positive association between elevations of GH and increases in Type II fiber sizethe elevations were determined to explain about 8 percent of the adaptations.
Take Away: Growth hormone can help build muscle, burn fat, and has an anti-catabolic effect. The overall muscle building benefits may be small, but the power of this hormone should not be ignored if you want to be lean, cut, and healthy.
4) Insulin-Like Growth Factor-1 enhances muscle gains via various signaling mechanisms in the body, including activation of dormant satellite cellsmuscle cells that wont grow unless activated.
IGF-1 doesnt appear to be necessary to build muscle for the average person, but it may lead to greater gains for the more advanced. A form of IGF-1 called Mechno Growth Factor, helps kick-start the post-workout muscle building process.
For example, one research analysis showed there were extreme hypertrophy responders, moderate responders, and non-responders in a 16-week training study. Mechano Growth Factor was 126 percent greater in the extreme responders compared to the non-responders.
Take Away: Greater IGF-1 and MGF response to training will enhance hypertrophy, especially for more advanced trainees. The ability to elevate these hormones and activate satellite cells is critical for maximal muscle growth and likely plays a role in strength development.
5) The alternative to the hormone hypothesis is that the purpose of post-exercise hormonal elevation is to mobilize fuel stores rather than promote tissue anabolism. The effect of appropriate training overload is still muscle development, but it happens due to enhanced protein synthesis that is not thought to be a direct result of hormone response. Nutrition, such as protein and carbohydrate intake, and availability of specific amino acids plays a role.
Take Away: Theres more going on with muscle and strength development than just the hormone response to training. Nutrition is critical as are other factors not reviewed here. The most important factor at a given time will be unique to the individual.
Schoenfeld, Brad. Post-Exercise Hypertrophic Adaptations: A Re-Examination of the Hormone Hypothesis and its Applicability to Resistance Training Program Design. Journal of Strength and Conditioning Research. 2013. Published Ahead of Print.