Interesting question... it really is...
My best friends observation.. from watching me.. she said that I was able to push my body to beyond the normal.. like supernatural - like supreme adrenal ..... then I "burned" out ,,, and then the cycle would start again..
her therory was that it is triggered by a need in my life each time.. maybe i wasn't even aware of what the need was.. and my body responded.. like a project due.. or my son needing something, or some social function so my body went into the "burst of energy" gear for a time..
Only.. unfortuately... my body permenatly "burned" out.. so I don't get that rush of energy.. the burst..
I don't know.. in my life... what she observed made sense...