Human growth hormone (hGH) is no doubt a potent stimulus for the formation of muscle mass and development of strength. As such, athletes who have done their homework seem to possess an advantage when it comes to resistance training. They have figured out not only the enormous benefit to eliciting elevated growth hormone levels during and following training, but also how to maximize this response by following a few simple training rules. This article will attempt to educate the reader to the role of hGH, and how to tailor training methods to naturally maximize the effectiveness of this powerful hormone. It will focus on the athlete interested in gaining lean body mass, and less on the athlete interested in strength gains exclusively.

Growth hormone is an anabolic hormone secreted by the anterior pituitary gland. For a reason that is not clearly understood, women have higher levels of growth hormone than men do. Levels of growth hormone in the body stay fairly level throughout the day and from day to day *, but seem to spike dramatically during and following heavy resistance training. As we will see, this "spike" has enormous significance to strength trainers and muscle builders. Growth hormone has the following effects in the body (2):

• Increases protein synthesis
  
  
• Increases utilization of fatty acids
  
  
• Increases availability of glucose and amino acids
  
  
• Increases collagen synthesis
  
  
• Stimulates cartilage growth
  

It is important to recognize that hGH does not work directly on muscle without help. In fact, growth hormone has few direct effects on muscle. Perhaps the most important role of growth hormone for muscle development is its stimulation of insulinlike growth factor (IGF). (2,3) Human growth hormone is critical in stimulating the production of IGF from liver sources. Although IGF spikes to some degree on it's own following resistance training, there is an even larger IGF response between 8 to 29 hours following heavy resistance training. This delayed response is from liver IGF sources and stimulated solely by growth hormone. In general, the greater the workout growth hormone response, the greater the IGF response during the next 8 to 29 hours. (2) IGF is one of the most potent anabolic hormones in the body.

Now that we have begun to understand the role of hGH in muscle development, lets look at what the resistance trainer needs to know to get the greatest possible growth hormone response from their training. First, Keep your repetitions around 10. (3) That is, choose a resistance load at or very near you 10 rep max for each set performed. Using higher or lower repetitions produces a far lower growth hormone response during and following training. One of the reasons for this is that growth hormone seems to be stimulated by lactic acid. Training at the 10 RM resistance load is highly glycolytic and produces the most lactic acid for the work performed. (2) It should be noted that although heavier loads produce a smaller growth hormone response, the athlete with exclusively strength goals, and no need for increased lean body mass or endurance (ex. the powerlifter) would still want to train with heavier loads and lower reps in accordance with the specificity principle.

Second, use short rest periods between sets. Rest periods of 30 to 60 seconds create very high lactic acid concentrations in the muscles, and accordingly create a larger growth hormone response than training with longer rest periods. (2) It is a common practice for resistance trainers to wait 2 to 3 minutes between sets of exercise, but it is not a smart practice for those who want to gain lean body mass and/or muscular endurance. For more see Pro Trainer back issues under the article "Rest Periods between Sets: everything you ever needed to know".

Third, use a variety of exercises to train each muscle. Using only one exercise will use only one set of motor units and muscle fibers. It is virtually impossible to train every muscle fiber in a muscle with only one exercise. It is proven that anabolic hormones have little to no effect on muscle fibers that are not stressed. Only a muscle fiber under stress will alter its sensitivity to an anabolic hormone. For this reason, if the muscle fiber is not being trained, it will not respond well to IGF. Incorporating as many different exercises as possible into each workout will aid your efforts to train as many muscle fibers as possible for maximum muscular response to IGF. (2)

Do not attempt to take hGH as an ergogenic aid. Its effectiveness is still very much under question. Early studies showed possible gains in fat-free mass, bone density, and reduced body fat. (4) Most recent studies have not been able to reproduce these results. If there is indeed an anabolic effect, it is most likely to effect older-age individuals. (1) The problem lies in the risks involved with taking supplemental hGH. Acromegaly, a thickening of the skin and bones resulting in broadening of the face, hands and feet is a possible side effect. In addition, muscle and joint weakness and heart disease are often associated with taking hGH. (4)

There are many things you can do with a resistance training program to naturally maximize the hGH, and thus the IGF response. Keeping these things in mind will help you design and implement highly effective lean body mass building programs. Please feel free to contact me with questions or comments at parsons@issaonline.com


* The level of hGH in women is much more unstable then that of men because of fluctuations in the menstrual cycle.

1) Eichner, Randy E. Ergogenic aids: what athletes are using - and why. Phys. Sportsmed. 25(4) 1997.

2) National Strength and Conditioning Association, Essentials of Strength Training and Conditioning. Champaign, IL: Human Kinetics. 1994.

3) Schoenfeld, B. Repetitions and muscle hypertrophy. Strength and Conditioning Journal. 22(6) 67-68.

4) Wilmore, J.H. Costill, D.L. Physiology of sport and exercise. Champaign, IL: Human Kinetics. 1994.