The study, published in the journal Breast Cancer Research,
followed more than 30,000 post-menopausal American women for 11 years.
Occurrences of breast cancer were noted and compared to exercise levels
in each woman.
The investigation separated exercise
levels into two categories: vigorous and non-vigorous. The vigorous
activities that cause an individual to break a sweat and increase heart
and breathing rate included running, fast jogging, competitive tennis,
aerobics, bicycling on hills and fast dancing. Chores such as scrubbing
floors, washing windows, heavy yard work, digging and chopping wood
We are often told that a little exercise, even if it is very light,
is better than none at all. While this is true, when it comes to
reducing breast cancer risk, light workouts proved ineffective. The
researchers categorized non-vigorous exercise as vacuuming, washing
clothes, painting, general gardening, walking, hiking, light jogging,
recreational tennis and bowling.
The study’s other significant finding
was that the breast cancer protection provided by vigorous exercise
applied only to women who were normal weight. Women who were overweight
or obese derived no safeguard from their workouts.
The authors propose that heavy women may
misreport non-vigorous activities as vigorous ones. This suggests the
possibility that if overweight females truly engaged in heart-pumping
behavior, they might also derive some protection.
Lead author Leitzmann states, “Possible
mechanisms through which physical activity may protect against breast
cancer that are independent of body mass include reduced exposure to
growth factors, enhanced immune function and decreased chronic
inflammation, variables that are related both to greater physical
activity and to lower breast cancer risk.”
A 30 percent reduction in one’s
likelihood of developing breast cancer is a sizable reward for staying
highly active. Yet there is also the benefit of decreased heart attack
and diabetes risk, better weight control and improved mood and mental