Photo: Mike Baird, Flickr

Obviously, exercise is good for you, but just how much it benefits you depends on many factors, including your gender and your race, according to a long-term study led by the University of Northern Carolina.

Researchers have been tracking exercise and cholesterol levels in 15,000 African American and Caucasian men and women since the late 1980s. In all groups, adding an hour of mild exercise or a half an hour of moderate exercise a week increased levels of 'good' cholesterol, the heart-healthy HDL kind. However, the increased activity lead to lower levels of LDL ('bad') cholesterol only in women, not men. Additionally, the only group to exhibit improvement in all cholesterol levels were African American women. Caucasians who exercised more saw a decrease in harmful triglycerides, but African Americans didn't show the same result.

The reason for the differences? Researchers aren't sure, but they suspect it has something to do with hormonal differences between the sexes and genetic difference between races. Furthermore, the method of research -- questionnaires -- means the results might not be entirely accurate.

If you're a woman, this is even more motivation to step it up, because it's evidence that even a small change can make a big difference. But regardless of your race or gender, regular exercise is vital to your heart health and overall well-being -- so get moving!

Need more motivation? Find out how Michelle Obama sculpts those smokin' arms.