https://heleo.com/conversation-how-c...r-brain/16689/
In a challenge state, your heart rate variability improves. Your blood vessels all dilate, you burn stored glucose, you get an increase in testosterone, you get a depression in cortisol, you get increases in adrenaline versus noradrenaline.
In a threat state, your heart rate variability drops. Your heart rate goes up, but you have vasoconstriction, so you’ve got all this blood rushing out of your heart, but it doesn’t have anywhere to go. Your fingers start getting tingly and numb. You get a burst of energy because you burn circulating glucose, not stored glucose.