Since exercise, by raising the level of metabolism, is known to cause increased free radical production, one might reasonably wonder--especially after all the negative comments I've made about free radicals--how this could be desirable. In a scenario similar to that with the blood vessels that rise to the occasion, exercise also teaches your body to expect more radicals. Even when you are not exercising, the added antioxidant protection remains, so you have better overall long-term protection. This is attested to by the following study.

In mice given voluntary wheel training (the rodent equivalent of a treadmill), levels of all three internally produced free radical scavengers (glutathione peroxidase, catalase, and superoxide dismutase) increased, while antioxidant protection (as measured by lower levels of oxidized fats in the blood) improved.

These findings show that even though exercise increases free radical production, it simultaneously trains the body to improve its free radical scavenging capacity, ultimately improving antioxidant protection. This added capacity for reduction of free radicals adds another dimension to Renewal, and it provides yet another mechanism to explain the anti-aging and life-extending effects noted for regular exercise in humans.