Exercises Done For Strength Not Endurance
Exercises with weights, for example, that are done for strength and not endurance, where the body is pushed to its limit  – these are the kinds of exercises that are the most efficient at raising HGH levels. Similarly, a hard-driving game of tennis is more effective in raising HGH levels than is a more leisurely game over a longer period of time. 
A recent study that points this out involved a number of women divided into three groups:
- 1st group would run a set distance of approximately 40 miles in a week, during a third of this distance on three different days, running it at a flat out rate.
- 2nd group would cover the same distance, but it was spread out over six days and was run at a more moderate pace.
- 3rd group was a control group and it did not run at all.
Surprisingly, only the first group showed strong increases in their HGH pulse levels.
Clearly, the second group would have benefited by strengthening their cardiovascular systems, as well as by gains in muscle tone and by burning off calories. But interestingly enough they didn’t show the solid HGH gains made by the first group that had ran harder and faster.
Of course, as expected the control group showed no change in HGH levels.
Similar studies have arrived at the same results. The take home here is, to raise the levels of HGH significantly with exercise, strenuous exercise works best.
Lower Body Exercises
It is possible that lower body exercises are more effective than upper body workouts when it comes to raising HGH levels.  If so, that may simply demonstrate the fact that the quadriceps and other leg muscles are among the largest in the body, and for that reason are better at raising HGH levels.
An added benefit to extended, strenuous exercise, is the euphoria feeling that often comes with it, brought on by elevated levels of brain beta-endorphins. Additionally, increased levels of endorphins have been shown to promote the increase of HGH. 
To what degree this represents the mechanism by which exercise raises the level of HGH is unclear. In fact, how exercise brings about increased levels of HGH is still a bit of a mystery among researchers. Undoubtedly, this is just another area of study currently showing a lot of promise to researchers.
 US National Library of Medicine. Growth hormone release during acute and chronic aerobic and resistance exercise: recent findings. Available from: http://www.ncbi.nlm.nih.gov/pubmed/12457419
 University of New Mexico. Hormones and Resistance Exercise. Available from: http://www.unm.edu/~lkravitz/Article%20folder/growthhormone.html
 The Doctors Medical Library. Human Growth Hormone (HGH). Available from: http://www.medical-library.net/content/view/180/41/
 US National Library of Medicine. The exercise-induced growth hormone response in athletes. Available from: http://www.ncbi.nlm.nih.gov/pubmed/12797841
 Livestrong Exercises to Increase HGH. Available from: http://www.livestrong.com/article/84066-exercises-increase-hgh/