The endocrine system is made up of endocrine glands, which include the pituitary, thyroid, parathyroids, adrenals, and pineal glands. Additionally, other organs of the body contain endocrine tissue, these being the hypothalamus, thymus, pancreas, ovaries, testes, kidneys, stomach, liver, small intestine, skin, and heart. The products of endocrine glands secrete into the space around secretory cells, then are diffused into capillaries and carried in the bloodstream.
The endocrine system, along with the nervous system, coordinate the functions of body systems. The nervous system prompts contraction of muscles, which causes secretion from glands. When the endocrine system releases hormones into the bloodstream, they are then carried to cells where they elicit responses. These responses may occur within seconds, or they may take hours to peak.
With regards to resistance training, the style of training being performed can help dictate the effects of the body’s systems. For example, heavy, low rep weightlifting with long rest periods works mainly by increasing the density of myofibrils within muscle cells and conditioning the nervous system to make impulses sent through neural pathways to muscles more efficient. More practice with movements results in more muscular force generation with that particular movement pattern. An example of this style of training would be barbell snatches for 3 sets of 3 repetitions with 5 minute rest periods between sets. By contrast, lighter loading parameters, more sets, and higher repetitions lean more towards sarcoplasmic hypertrophy, filling muscle cells with fluid — typical bodybuilding style workouts are geared more towards this purpose. As I’ll discuss in a minute though, higher volume routines can elicit heightened hormonal responses. Obviously, there is neuroendocrine overlap regardless of training style, but my point is that the volume and intensity of effort can be manipulated to achieve varying physique and performance goals.
I’ll cover myofibrillar and sarcoplasmic hypertrophy in more detail in a future article, but for the moment do me a favor and visualize an overly vague (and potentially unfair) generalization: Primarily myofibrillar hypertrophy = olympic weightlifter. Primarily sarcoplasmic hypertrophy = “pumped up” Jersey Shore nightclub attendee.
Ah, I digress. Back to hormones… for now, let’s focus on the most buzz-worthy glandular secretions in the gym:
Testosterone is a steroid hormone, having both androgenic and anabolic effects. It is produced primarily by the testes in males, and to a lesser extent, the adrenal glands. The metabolic effects of testosterone include muscle mass, strength, and energy. The anabolic effects of testosterone include muscle tissue growth and bone density.
Growth Hormone is a protein based peptide hormone. It is secreted by the pituitary gland for the purpose of cell regeneration. The primary action of GH is the growth of body cells. It also has multiple metabolic effects, most notably the stimulation of protein synthesis, inhibition of protein breakdown, and elevating blood glucose concentration.
The difference between a peptide hormone and a steroid hormone is a steroid hormone binds directly to cells, where peptide hormones use secondary messengers. GH, being a peptide, uses assistance from Insulin-like Growth Factor-1 for cellular response. IGF-1 is produced mostly by the liver, with GH being the primary stimulator.
GH causes cellular growth by increasing the speed of amino acids as they enter into cells. This increases protein synthesis. GH also decreases the breakdown of proteins used to generate ATP, instead using fat oxidation for energy. This means that increased levels of GH in the body cause fat to burn as fuel instead of muscle. Additionally, GH affects carbohydrate metabolism, causing the liver to convert glycogen into glucose.
If you’re wondering why our beloved professional athletes are so infatuated with synthetic Testosterone, GH and IGF-1 supplementation, wonder no more. Simply put: optimized hormonal release = enhanced muscle hypertrophy, less stored fat, and more efficient metabolic processes.
Resistance exercise has long been known to elicit a hormonal response to stimulus. As long as the volume (sets and repetitions) and intensity (percentage of 1-rep maximum) of resistance exercise is sufficient, Testosterone and Growth Hormone are elevated following a lifting session. Levels generally peak about 15-30 minutes after lifting.
A study conducted by Kraemer and Ratamess at The University of Connecticut states:
“Protocols high in volume, moderate to high in intensity, using short rest intervals and stressing a large muscle mass, tend to produce the greatest acute hormonal elevations (e.g. testosterone, GH and the catabolic hormone cortisol) compared with low-volume, high-intensity protocols using long rest intervals.”
The full abstract can be found here: http://www.ncbi.nlm.nih.gov/pubmed/15831061
The above findings suggest that a greater volume of training has a larger effect on hormonal release, provided that the training isn’t so debilitating that excess amounts of cortisol begin to circulate.
The highly successful Bulgarian olympic weightlifting teams of the 1970’s coached by Ivan Abadjiev kept heavy training sessions limited to 45 minutes each because they believed that testosterone production leveled off after that point. While there isn’t much scientific evidence to support the 45 minute theory, it’s hard to argue with the Bulgarian methods. Bulgarians have won 36 olympic weightlifting medals even though their country has a population of approximately 7,364,570. To put that accomplishment into perspective, the United States has won 43 olympic weightlifting medals, with an approximate population of 316,123,000. Yes, the Bulgarian teams have, in the past, occasionally been caught doping, but so has every other nation that has succeeded in international athletic competition. Their steroids aren’t better than everyone else’s steroids.
Some bullet points to, uh… synthesize this information…
To maximize testosterone and GH levels with resistance exercise:
- Use lifts that recruit a large amount of muscle mass (Example: Squat, Bench Press, Row).
- Perform a sufficient volume (sets x reps x load) of resistance training (Example: 3-6 sets x 6-8 repetitions per lift).
- Utilize compressed rest periods between sets, ideally between 30-90 seconds.
- Keep total training session times long enough to maximize Testosterone and GH levels, but minimize Cortisol. Though there is a dearth of scientific study on the topic, the anecdotal evidence supporting 45-60 minutes of intense exercise is strong.
- In addition to exercise and nutritional choices, lifestyle factors play a huge part in maintaining hormonal balance. The most notable of these elements are getting adequate sleep and lowering stress levels.
Though these general tips can prove useful, keep in mind that each human body in unique. Use scientific processes to experiment for your own purposes: hypothesis, controlled variables, observation, testing, analysis, and modification. Accordingly, if you’re not already keeping a detailed training journal to track your progress, start one immediately.
More detail on these topics will be included future articles…
Faigin, Rob. “Hormonally Intelligent Exercise.” Extique. 2004.
Karp, Hannah. “Heavy Lifting, No Rest, Candy: the Bulgarian Method.” The Wall Street Journal. June 21, 2011. http://online.wsj.com/article/SB10001424052702304070104576397543601842556.html
Kraemer WJ. “Endocrine responses to resistance exercise.” Med Sci Sports Exerc. 1988 Oct;20(5 Suppl):S152-7. Exercise Physiology Division, U.S. Army Research Institute of Environmental Medicine, Natick, MA 01760-5007.
Kraemer WJ, Ratamess NA. “Hormonal Responses and Adaptations to Resistance Exercise and Training.” Sports Med. 2005;35(4):339-61. Human Performance Laboratory, Department of Kinesiology, University of Connecticut, Storrs, 06269, USA.
Poliquin, Charles. “Five Lessons I Learned from Ivan Abadjiev.” November 11, 2010. http://www.charlespoliquin.com/ArticlesMultimedia/Articles/Article/491/Five_Lessons_I_Learned_from_Ivan_Abadjiev.aspx
The Medical Biochemistry Page. http://themedicalbiochemistrypage.org/growth-factors.php#igf1
Tsatsouline, Pavel. “Power To The People.” Dragon Door Publications. 1999.
Verkhoshansky, Yuri. “Supertraining, 6th edition.” 2009.
Wikipedia. “Bulgaria.” http://en.wikipedia.org/wiki/Bulgaria
Wikipedia. “United States.” http://en.wikipedia.org/wiki/United_States
Zatsiorsky, Vladimir. “Intensity of Strength Training Fact and Theory: Russian and Eastern European Approach.” Biomechanics Lab The Pennsylvania State University, University Park, Pennsylvania and Central Institute of Physical Culture – Moscow, Russia