How much exercise do women need to reduce their risk of breast cancer?

That's the question a Calgary researcher hopes to answer with an Alberta-based study of 400 healthy, post-menopausal women that will compare the impact of moderate and high-level exercise regimes on risk factors associated with breast cancer such as body fat and hormone levels.

According to previous studies, women with high levels of recreational activity had a 25 to 30 per cent reduction in their breast cancer risk when compared with inactive women.

"This is actually a really large risk reduction when you think about how little women can actually do to reduce their risk of breast cancer," lead researcher Christine Friedenreich told CBC News.

The current trial will determine which amount of cardiovascular exercise — either 150 minutes or 300 minutes per week — has the greater benefit.

For the participants, who must exercise for either 30 or 60 minutes, five days per week for one year, the benefits include more than cancer prevention.

No downside to exercise

As a result of participating in the study, Vicki Babcock, 58, says her heart rate has improved, she is sleeping better and she no longer needs coffee to wake up in the morning.

"There's no downside to this," says Babcock, who has nearly completed her participation in the year-long research in Calgary. The exercise intensity is like a brisk walk, said Christine Friedenreich. (Courtesy Christine Friendenreich)

Shannon Brown, a personal trainer working with the study participants, said she has seen many positive developments in the group, including improved mental health, physical health and quality of life.

"Some ladies have gone off their blood pressure medication," she says. "They’re just that much fitter."

However, the time commitment is significant, especially for the group of women who must work out for 300 minutes per week. Fitting the exercise regime into her schedule requires planning, said Babcock, a real estate agent.

"I typically come to the gym earlier in the morning so that I can get on with my day," she said.

As for the exercise itself, "It is something that anyone can do," Friedenreich says. "So long as they can do brisk walking, [everyone] can reach the targeted intensity that we’re looking for in this study."

First of its kind

Friedenreich said her study through Alberta Health Services Cancer Care is the first of its kind to examine the dose of physical activity needed to reduce the risk of breast cancer. About 200 studies worldwide have looked at some type of physical activity as a means to prevent cancer.

According to the Canadian Cancer Society, about half of all cancers can be prevented by factors such as diet and exercise, avoiding tobacco, reducing long-term sun exposure and lessening alcohol consumption.

This week CBC News reports on the search for cures for aging, Type 1 diabetes, the common cold, obesity and cancer on CBC Radio One, CBC News Network, The National and at cbc.ca/news/health/.