For women, getting into the habit of being physically active when you're young influences the likelihood you'll be active later in life, helping to cut the risk of coronary heart disease, researchers report.

A large study of nearly 40,000 women indicates women who were the most active during their teens and between the ages of 18 and 22, continued to be active at middle-age and beyond.

"This large study of women indicates a strong relationship between vigorous physical activity in young adulthood and achieving recommended levels of activity at middle age," writes researcher Molly Conroy and colleagues in the article, published in the journal, Medicine & Science in Sports & Exercise. "Young women who are active are more likely to be active later in life, when rates of Coronary Heart Disease (CHD) increase and physical activity in middle age clearly predicts lower risk of CHD."

The study examined participants in the Women's Health Study who were aged 45 or older. Women were surveyed about their physical activity patterns over the course of two years and were then followed for an average of nine years to track the occurrence of CHD.

"The most active women…during high school and age 18 to 22 years were more than twice as likely to meet physical activity recommendations at baseline than the least active women," the investigators note.

The evidence did not show that being active in younger years would necessarily lead to a lower risk for CHD as women age, but the researchers still say results drive home the importance of physical activity in general. "Although physical activity in young adulthood did not predict lower CHD rates later in life, it should still be encouraged, as it correlates strongly with being active later in life when CHD is more prevalent," the researchers state. "(Therefore), the present study provides empirical data to promote physical activity in young women."

The investigators note the study has certain limitations, including its reliance on women self-reporting their physical activity patterns, which could be tampered by bias or difficulty with recall. They also stress that "more detailed information and research is needed."