Life is busy, and some folks simply don't have time until the weekend to work out. Turns out, that's just fine for their health, a new study suggests. Advertisement "Weekend warriors" who cram their week's exercise into one or two days appear to gain as much benefit as people who are physically active throughout the week, researchers reported Wednesday in the Journal of the American Heart Association . "You don't need to exercise every day to stay healthy," senior researcher Zhi-Hao Li , an