Women active a few times weekly have lower risk of heart disease, stroke and blood clots

In the study:

• Women who performed strenuous physical activity -- enough to cause sweating or a faster heart beat -- two to three times per week were about 20 percent less likely to develop heart disease, strokes or blood clots compared to participants who reported little or no activity.

• Among active women, there was little evidence of further risk reductions with more frequent activity.

Physical activities associated with reduced risk included walking, gardening, and cycling.

"Inactive middle-aged women should try to do some activity regularly," said Miranda Armstrong, M.Phil., Ph.D, the study's lead author and a physical activity epidemiologist at the University of Oxford in the United Kingdom. "However, to prevent heart disease, stroke and blood clots, our results suggest that women don't need to do very frequent activity as this seems to provide little additional benefit above that from moderately frequent activity."

Participants included 1.1 million women in the United Kingdom with no history of cancer, heart disease, stroke, blood clots, or diabetes who joined the Million Women study in 1996-2001. Their average age when they joined the study was 56.

The women reported their level of physical activity at the beginning of the study and three years later. Researchers then examined hospital admissions and deaths in relation to participants' responses. Follow-up was, on average, nine years.