myostatin is the gene that controls/limits muscle growth, we are meant to survive, not be beautiful... so this gene keeps us from getting bigger than we "need" to be to survive in nature.
there was a study done (on humans, using testosterone) that myostatin expression increased substantially after 56 days of administration in response to the drug.
by adding another compound, or increasing the dose of compounds that are already being used, you can circumvent, in a way (for a time), the increase in myostatin expression.
this is why guys blast for 8 weeks, and then cruise for 2 (the slingshot method). it is believed that 2 weeks is enough time to allow myostatin expression to return to normal levels.
it is for this reason that "oral kickstarts" and "frontloading" are nonsensical if the cycles are to last more than 8 weeks.. employing these methods simply desensitize your body to higher doses more quickly, as myostatin expression increase should somewhat correlate with your dose if I recall correctly.
it would be far more effective to begin using the orals after 8 weeks, or up the dose instead of front loading after 8 weeks.