New Scientist recently produced a a study demonstrating that fairly low doses of anabolic steroids boost performance in just weeks:
The first rigorous study of the performance-enhancing effects of testosterone in young men was not carried out until 1996. Volunteers were given weekly injections of either 600 milligrams of testosterone enanthate or a placebo for 10 weeks (bodybuilders usually take much larger doses). Performance tests done at the end of this period showed the hormone had improved muscle size and strength in those doing strength training, and to a lesser extent in those who did not exercise.
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In the latest study, Weatherby monitored the performance of 18 male amateur athletes over a six-week training regime. Nine were given weekly shots of testosterone enanthate at a dose of 3.5 milligrams per kilogram of body weight for six weeks (equivalent to roughly half the dose of the 1996 trial), and nine were given a placebo.
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The most unexpected finding was that the greatest increases in muscle size and power occurred just three weeks into the trial.