Consistent exercise timing acts as an entrainment cue that reinforces the timing of cortisol release from the SCN.

“Exercise, Entrainment Cues & Cortisol Rhythm, Tool: Boost Energy & Exercise Schedule”

“So there are these beautiful interactions between exercise, the SCN, and cortisol release that when we exercise at roughly the same period of time each day, doesn't have to be right on the minute, but within the same two or three hour window each day...”