Women who undertake moderate exercise, such as brisk walking, may reduce their risk of suffering a stroke by 20%, a new study indicates.

Moderate exercise may also partially offset some of the increased stroke risk associated with post-menopausal women who are taking HRT (hormone replacement therapy).

US researchers looked at over 133,000 women to see how many had suffered a stroke between 1996 and 2010. They found that those who undertook moderate physical activity in the three years before starting in the study were 20% less likely to go on to suffer a stroke compared to those who did not undertake any activity.

"The benefits of reducing risk of stroke were observed among the group of women who had a sustained moderate level of physical activity over time," the researchers noted.

They said they were ‘surprised' that moderate activity ‘was most strongly associated with a reduced risk of stroke'.

"More strenuous activity such as running didn't further reduce women's stroke risk. Moderate activity, such as brisk walking, appeared to be ideal in this scenario," they pointed out.

The study also found that women taking HRT had a 30% increased risk of suffering a stroke compared to women who did not take it. This risk started to decline when they stopped taking HRT.

However, those on HRT who undertook moderate activity had a reduced risk of stroke compared to those on it who did not exercise.

"The effects of physical activity and hormone therapy appear immediate and the benefits of physical activity are consistent in pre-menopausal and post-menopausal women," the researchers from California said.

They emphasised that activities such as brisk walking and recreational tennis do not require gym memberships.

"You don't have to do an extreme boot camp. The types of activities we're talking about are accessible to most of the population."

The researchers presented their findings at the American Stroke Association's International Stroke Conference 2014 in San Diego.