Why when I take walks to exercise my legs and lower back start to hurt with in a matter of minutes?

Depends on... Your level of physical fitness, your weight, the health of your blood vessels, and your overall health status. These problems could be related to carrying around excess weight, being out of shape, or problems with your blood vessels. The only way to know for sure is to see a physician. It could also be related to the shoes you are wearing or your need for arch support.