Acromegaly patients, who suffer from natural growth hormone levels of up to 100 times higher than normal, have lower stamina towards physical activity than people with regular levels.  When the patients are treated and their growth hormone levels decrease, their stamina improves.  This knowledge is part of the evidence behind the new belief that athletes who use supplemental HGH to raise their levels far above average could actually decrease their exercise tolerance, and thus hurt their athletic performance.  Further backing was provided in a study done by the Danish Institute of Sports Medicine. They found cyclists of good health and endurance “were unable to complete accustomed cycling tasks after administration of exogenous hGH” and concluded that HGH can inhibit recuperation from exercise.  Participants have also been found to have lower stamina after HGH treatment along with higher rates of fatigue. 
If you're going to use any injectable gear, then of course you're going to need some "darts." You can pick up syringes at your local pharmacy unless your state has certain restrictions. Also, you can purchase needles online. Just do a little searching around and you'll find several places that'll hook you up. Syringes will run you around 50 cents apiece. Note that it'll be more difficult to obtain needles (at least from the larger, more "legit" companies) if you live in California and Illinois. You'll usually need a doctor's prescription in those states. Still, if you look around enough, you can get what you need.