To keep the body in good health is a duty. Otherwise we shall not be able to keep our mind strong and clear. ~ Buddha
Norepinephrine is a hormone and neurotransmitter central to concentration, motivation, pain, and stress response. Lactate provokes the adrenal gland to release norepinephrine (C8H11NO3), which is synthesized from dopamine (C8H11NO2), a similar neurotransmitter and hormone.
Astrocytes are the principal source of brain lactate. By releasing lactate to invoke norepinephrine, these glia cells regulate awareness level.
C6H12O6 is broken down for energy and oxidized to pyruvate (C3H4O3). With anaerobic exertion, lactate (C3H6O3) is produced from fermented pyruvate faster than tissues can flush it, and so accumulates. With moderate production, lactate is beneficial in ensuring continued energy production for physical exertion.
Meanwhile, the chemical chain of exertion – lactate → norepinephrine – maintains high awareness on the moment. Hence, from an evolutionary perspective, there is mind-body readiness for responsive action. This also explains how physical exercise keeps the mind fit as well the body.
More generally, physical exercise releases hormones throughout the body, including in the brain, that sharpen physical performance. Mental acuity is maintained by being focused at the task at hand.
A cousin of norepinephrine, also produced by the adrenal glands during exercise, is adrenalin (C9H13NO3). Adrenalin stimulates the immune system, most notably the production of natural killer (NK) cells. NK cells are especially effective at suppressing the growth of tumors. This is how regular exercise acts against cancer.
Regularly exercising the body is essential in maintaining health. It is a habit to be cultivated early in life. From a life cycle viewpoint, one either earns dividends for exercise or pays in the back end for sloth in the first half of life.