I´ve been wondering why when people exercise the lower abdominals, feel so great. I personally have experienced that feeling, doing some pilates routine, or there´s a serie called navel power in kundalini yoga,... after stimulaiting the area betwen the navel and the pubis; my head is clear and my language precise, I feel a sense of wellbeing.
There has to be a powerfull link betwen serotonin and exercising the lower abdominals.
In martial arts is the center of power, in pilates it's called the power house.