Overall , the current literature supports clearly the dose-response relationship between physical activity and the seven chronic conditions identified .
Moreover , higher levels of physical activity reduce the risk for premature all-cause mortality .
The current Canadian guidelines appear to be appropriate to reduce the risk for the seven chronic conditions identified above and all-cause mortality
This systematic review examines critically the scientific basis for Canada 's Physical Activity Guide for Healthy Active Living for adults .
Particular reference is given to the dose-response relationship between physical activity and premature all-cause mortality and seven chronic diseases ( cardiovascular disease , stroke , hypertension , colon cancer , breast cancer , type 2 diabetes ( diabetes mellitus ) and osteoporosis ) .
The strength of the relationship between physical activity and specific health outcomes is evaluated critically .
Recreational physical activity and the risk of breast cancer in postmenopausal women: the Women's Health Initiative Cohort Study.
CONTEXT Women who are  physically active  have a decreased risk for breast cancer , but the types , amounts , and timing of activity needed are unknown . OBJECTIVE To prospect ively examine the association between current and past recreational physical activity and incidence of  breast cancer in postmenopausal women . DESIGN , SETTING , AND PATIENTS Prospect i ve cohort study in 74 171 women aged 50 to 79 years who were recruited by 40 US clinical centers from 1993 through 1998 . MAIN OUTCOME MEASURE Incident invasive and in situ breast cancer . RESULTS We documented 1780 newly diagnosed cases of breast cancer over a mean follow-up of 4.7 years . Compared with less active women , women who engaged in regular strenuous physical activity at age 35 years had a 14 % decreased risk of breast cancer ( relative risk [ RR ] , 0.86 ; 95 % confidence interval [ CI ] , 0.78 - 0.95 ) . Similar but attenuated findings were observed for strenuous physical activity at ages 18 years and 50 years . An increasing total current physical activity score was associated with a reduced risk for breast cancer ( P = .03 for trend ) . Women who engaged in the equivalent of 1.25 to 2.5 hours per week of brisk walking had an 18 % decreased risk of breast cancer ( RR , 0.82 ; 95 % CI , 0.68 - 0.97 ) compared with inactive women . Slightly greater reduction in risk was observed for women who engaged in the equivalent of 10 hours or more per week of brisk walking . The effect of exercise  was most pronounced in women in the lowest tertile of body mass index ( BMI ) ( < 24.1 ) , but also was observed for women in the middle tertile of BMI ( 24.1 - 28.4 ) . CONCLUSIONS These data suggest that increased physical activity is associated with reduced risk for breast cancer in postmenopausal women , longer duration provides most benefit , and that such activity need not be strenuous
Overall , the current literature supports clearly the dose-response relationship between physical activity and the seven chronic conditions identified .
Moreover , higher levels of physical activity reduce the risk for premature all-cause mortality .
The current Canadian guidelines appear to be appropriate to reduce the risk for the seven chronic conditions identified above and all-cause mortality
This systematic review examines critically the scientific basis for Canada 's Physical Activity Guide for Healthy Active Living for adults .
Particular reference is given to the dose-response relationship between physical activity and premature all-cause mortality and seven chronic diseases ( cardiovascular disease , stroke , hypertension , colon cancer , breast cancer , type 2 diabetes ( diabetes mellitus ) and osteoporosis ) .
The strength of the relationship between physical activity and specific health outcomes is evaluated critically .