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 .
Physical activity and breast cancer risk in a cohort of young women.
BACKGROUND Increased physical activity has been hypothesized to be a means of breast cancer prevention . We examined the associations between physical activity at two different times in life and breast cancer risk . METHODS We analyzed data from the Nurses ' Health Study II , a prospect i ve study of women aged 25 - 42 years in 1989 . On the baseline survey , women were asked , " While in high school and between the ages 18 and 22 years , how often did you participate in strenuous physical activity  at least twice a week ? " We averaged answers to these two questions to develop a measure of late adolescent activity . Women were also asked at baseline to report the number of hours per  week they currently spent in different nonoccupational activities . During 6 years of follow-up , we identified 372 cases of invasive breast cancer . Data were analyzed by use of multivariate pooled logistic regression to produce relative risk ( RR ) and confidence intervals ( CIs ) of being diagnosed with the disease . RESULTS Women who were more active in late adolescence were not at reduced risk of breast cancer compared with less active women . For those women who reported engaging in strenuous activity at least twice per week for 10 - 12 months per year in late adolescence , the RR of cancer , compared with those who never engaged in such activity , was 1.1 ( 95 % CI = 0.8 - 1.6 ) . Similarly , higher levels of recent nonoccupational physical activity were not associated with reduced risk of breast cancer ( RR for > or = 7 hours of activity/week relative to < 1 hour/week = 1.1 ; 95 % CI = 0.8 - 1.5 ) . CONCLUSION Our findings do not support a link between physical activity , in late adolescence or in the recent past , and breast cancer risk among young adult women
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 .