The American College of Sports Medicine (ACSM) will publish a study in the September 2001 issue of its official monthly journal, Medicine & Science in Sports & Exercise(R) that examines the importance of physical activity to the risk of breast cancer. The study measured the influence of frequency, duration and intensity of physical activity on the risk of breast cancer, and compared the risk associated with self-reported activity level as opposed to assigned energy- expended intensity levels.

"We knew that women who are physically active reduce their risk of breast cancer," said Christine M. Friedenreich, Ph.D., lead researcher. "We were interested in defining the relationship more precisely in the interest of developing public health recommendations." Friedenreich, who is an epidemiologist with the Division of Epidemiology for the Alberta Cancer Board in Calgary, Alberta, joined forces with faculty from the University of Alberta in Edmonton in designing a study that would examine all parameters (frequency, intensity and duration) and all types (occupational, recreational and household) of activity throughout a woman's lifetime. The study then would compare self-reported as opposed to assigned levels of energy expenditure for specific activities.

The population-based study, which ranged over two years and worked with 1233 cases and 1237 controls, used the interview- administered Lifetime Total Physical Activity Questionnaire. All women with newly diagnosed breast cancer in Alberta in 1995-97 were compared with population controls recruited by telephone; women in the control group had to be free of cancer diagnosis. The researchers gathered information on each woman's menstrual history, reproductive episodes, hormone use, mammogram results, breast disease, and pertinent family history of cancer. They also asked about lifetime physical activity patterns, dietary history, alcohol use and smoking habits. Each participant was given two "recall" calendars designed as memory aids for the women to use for reporting long-term physical activity throughout their lives.

Data were analyzed in two parts. The first analysis used self-reported intensity values based on the participants' descriptions; the second one used a definition obtained from the Compendium of Physical Activity (published in Medicine & Science in Sports & Exercise(R) Volume 25) and assigned to the individual respondent's data. Both case and control groups were comparable in total lifetime physical activity values; moreover, no meaningful differences were discerned in the average number of hours per week spent in physical activity.

Results of the study indicate that the greatest risk reduction for breast cancer is found in moderate intensity occupational (performed in the course of such work as farming, assembly-line, retail or domestic work) or household activity (performed in the course of such work as laundry, gardening, household repair and child-care activities) as opposed to recreational activity of any intensity. Also, frequency and duration were more important than intensity in any case. The researchers noted that occupational activity as a source of physical activity in North America will continue to decline with increasing mechanization, so more effort toward maintaining levels of physical activity will be necessary in order to support the protective effect of physical activity on breast cancer risk.

The American College of Sports Medicine is the largest sports medicine and exercise science organization in the world. Nearly 18,000 members throughout the United States and the world are dedicated to promoting and integrating scientific research, education, and practical applications of sports medicine and exercise science to maintain and enhance physical performance, fitness, health, and quality of life.