Human Growth hormone is a powerful substance produced in the body. It tends to be produced and released in a pulsatile manner, often revolving along our circadian rhythm.
Its primary role is the growth of bodily tissues and is often at its highest peak younger in age while we are growing rapidly and begins to slowly decrease as we grow older. Gender also plays a role in how much growth hormone we release, with females surprisingly releasing more than males.
Growth hormone is involved in the turnover of muscle tissue, which is particularly important for those of us who are looking to add lean muscle mass, as well as the remodeling of bone and collagen tissues (Godfrey, R., et al., 2003).
It also helps with the regulation of our metabolisms, which are essentially all the reactions that occur within the human body.
Two of the biggest factors that play a role in the release of this hormone are sleep and exercise.
1 / Sleep
Generally, our growth hormone release is highest during the first part of the night, which is why getting to bed at a decent time for a good nights rest is so important.
When we cut our sleep short, we blunt the effect of growth hormone, thus also limiting our recovery and muscle growth ability.
2 / Exercise
Exercise is probably the largest contributor to growth hormone release. Exercise appears as though it effects the growth hormone release through numerous different mechanisms such as:
- Neural Input
- Direct stimulation by catecholamines
- Lactic & nitric oxide
- Changes in acid-base balance (Godfrey, R, et al, 2003)
Different types of exercises impact the HGH in different ways however.
Resistance training offers one of the most influential environments for exercise induced growth hormone release (EIGR). The major factors that determine how much an increase is produced are load and frequency.
When we lift heavier loads at a greater frequency (less rest time) we cause our bodies to release greater amounts of growth hormone.
It should be noted however that in regards to protein synthesis, insulin-like growth factor-1 plays a larger role than growth hormone does.
Resistance training programs that utilize many large muscle groups at once tend to elicit the greatest growth hormone release as more total muscle fibers are called into play. Also, growth hormone release tends to depend upon how much of a demand on anaerobic glycolysis there is during an exercise training bout.
With endurance training, the release of growth factor depends on intensity, duration, frequency as well as the type of exercise performed. Exercise performed above the lactate threshold for at least 10 minutes will create the greatest growth hormone release both during exercise and for the 24 hour period afterwards (Godfrey, R, et al, 2003).
Due to the pulsatile release of growth hormone, the optimal environment for the release are shorter bouts of exercise performed for 10 minutes several times daily at an intensity greater than lactate threshold.
Endurance training however, when taken too far, can actually cause a decreased effect on growth hormone release. When it lasts for longer periods of time, and is performed for a long duration, growth hormone decreases while cortisol (the hormone responsible for breaking down the body's tissues) increases.
So it is essential to push your body hard enough during your cardio training to increase the release of the hormone, however care has to be taken not to over due it (overtraining) where your body can no longer recover and you move towards a catabolic state.
Aging & Growth Hormone
Another thing growth hormone is known for is its effect on the aging athlete. As we age, we tend to lose muscle mass and increase our fat mass. This means a change in body composition resulting in a higher body fat percentage, which sets up for risks of many different types of disease such as high cholesterol levels and blood pressure.
Growth hormone however, tends to produce changes in the body that are exactly opposite of this, increasing lean muscle tissue and decreasing body fat. For this reason, some aging people decide to start injecting growth hormone into their bodies to reap its benefits.
While these individuals do report an increase in lean mass and decreased fat mass, there are also other negative consequences such as impaired glucose tolerance that may provide enough reason to avoid this practice.
Rather, a better way to get the rewards of this hormone, are for the aging athlete to perform exercise at a higher intensity than what is normally prescribed for someone of this age level.
It has been demonstrated that while older athletes do not see quite the acute increase in growth hormone following a resistance training protocol that younger athletes do, their chronic growth hormone levels do increase the same way and they will still see the benefits of this hormone (Godfrey, R., et al, 2003).
Take Home Message
So what is the take home message from these studies? How can you use this knowledge to help benefit your training?
The first thing is to evaluate your workouts and determine whether you are more of a resistance athlete or an endurance athlete.
If you are a resistance athlete, then you need to look at your workouts and ensure that you are lifting the correct loads and utilizing the right rest periods to elicit a greater release of growth hormone from your training.
On the other hand, if you are an endurance athlete, you may want to consider adding some high intensity interval work into your training so you too can benefit from growth hormone, and also may want to take proper nutritional steps to ensure that on your longer sessions you minimize the catabolic properties of these types of workouts (since they tend to produce a decline in growth hormone).
- Godfrey, R., Madgwick, Z., & Gregory, P.W. (2003). The Exercise-Induced Growth Hormone Release in Athletes. Sports Medicine: 33 (8).