Growth Hormone

Growth hormone (GH) is a hormone made by your pituitary gland (which is located at the base of the brain) that has important roles in training and recovery.  Growth hormone is responsible for increasing glucose uptake in muscle, enhancing protein synthesis in the liver and muscle, and causing the breakdown of fat.  GH is released primarily during sleep and during exercise.  This section will discuss the importance of GH and how to maximize its release.

As the major hormone that your body produces that is responsible for building muscle and recovery, the secretion of GH is critical to every athlete.  GH is anabolic; which means that it helps increase muscle mass.  Additionally, GH increases fat mobilization and decreases fat deposition, leading to an overall decrease in body fat.  So, I think we have established that GH is some good stuff.  So how do we get our body to maximize the production of GH?

Since GH is released when you sleep, it must follow that SLEEP is also critical to every athlete.  Many elite athletes are known to take naps during the day between work-outs.  This not only provides them with additional rest, but it also increases GH secretion.  Of course it is unrealistic for most working athletes to be able to take naps (unless you live and work in a region that practices the siesta), therefore getting adequate sleep must be a major priority.  Sacrificing sleep results in sacrificing release of growth hormone which leads to inadequate recovery.  This becomes important when one consistently deprives the body of adequate sleep in order to wake-up to complete that early morning work-out. 

Additionally, GH release is based on the body's circadian rhythms.  More GH is released during the earlier hours of the night then the later hours.  Thus, sleep schedules are also important as 8 hours of sleep from 10 pm to 6 am causes greater GH release than 8 hours of sleep from midnight to 8 am.  The above diagram shows pulses of growth hormone corresponding to the four sleep cycles that occur during an average good night's sleep.

Exercise and physical stress also increase GH levels, however the majority of GH release occurs during sleep.

Hyperglycemia, as in that which occurs after the Insulin (discuss effects of insulin).  Another effect of insulin is inhibiting secretion of GH.  After eating insulin increases...  Because of the inhibitory effects of insulin on GH, one will not achieve maximum GH secretion if a work-out is done within 2 to 3 hours after eating.  After 2 to 3 hours, insulin levels return to normal.  Therefore, to obtain optimal GH secretion, try to schedule work-outs 2 to 3 hours after eating.

Easier said then done, right?  Often with the busy life-style of the age-group triathlete it is difficult to schedule work-outs around eating and meals.  We all know the feeling of leaving work to go work-out with an intense feeling of hunger.  I have two recommendations: (1) hold off eating until 20 to 30 minutes into the work-out.  After 20 to 30 minutes GH secretion has started, and consuming calories will not jeopardize GH secretion.  (2) Eat something that has a low glycemic index (GI).  Foods that are low in simple sugars will have a low GI (click on the link to learn more about glycemic index), which will cause less insulin secretion, which will have a smaller inhibitory effect on GH secretion.

Hypoglycemia, or low blood sugar, is another problem that can be caused by eating too soon before a work-out.  Consuming food with a high GI will result in a significant amount of insulin secretion.  The actions of the insulin moving glucose from the blood into muscle coupled by the muscles' utilization of glucose can result in low blood glucose that will be noticed 15 to 30 minutes into a work-out.  Symptoms include weakness, lightheadedness, dizziness, and nausea (anymore sx's?).  Examples of high glycemic index foods that should be avoided prior to a work-out include gels, cola, cookies, etc.  A simple solution to this dilemma is to consume some gel or an energy drink, preferrably one with complex carbs (maltodextrin, for example) and a low glycemic index.