Muscle cells are primed to incorporate amino acids and synthesize muscle in the morning due to circadian regulation.

“So, what this means is that when you wake up in the morning, assuming you're following a standard schedule of being asleep at night and awake during the day, your muscle cells are primed to incorporate amino acids and synthesize muscle, regardless of whether or not you weight trained the night before 8:00 P.M., or you don't weight train at all, or you weight train afterwards or before.”