(Exercise) “may contribute even more directly (to boosting your immune system) by promoting good circulation, which allows the cells and substances of the immune system to move through the body freely and do their job efficiently.” In one study in the American Journal of Medicine, women who walked for a half-hour every day for 1 year had half the number of colds as those who didn't exercise. Researchers found that regular walking may lead to a higher number of white blood cells, which fight infections. Weighted walking not only helps build immunity but may contribute to better bone health and bone density.