It Weakens Your Bones
As many as half of adult Americans are affected by bone loss. Ten million live with osteoporosis, and even more -- about 43 million more -- have lost enough bone mass that they're at a high risk of developing osteoporosis, according to the National Osteoporosis Foundation [source: NOF]. To strengthen your bones and prevent osteoporosis, you need to stand up. Bones need to support your weight -- or some weight -- regularly in order to stay strong; otherwise they lose their density and become brittle and weak.
Daily walking will help you make strides against osteoporosis, as well as both weight-bearing exercises and resistance training. Exercises that put a little pressure on those bones keep bone loss at bay (and it'll also build muscles and keep you flexible, too).