Background: The observation that exercise training reduces cardiovascular mortality is robust and consistent, but the amount and intensity of exercise that is required for risk reduction is not yet resolved.
Methods: We studied the association between the amount and intensity of exercise and cardiovascular mortality in 27 143 men and 28 929 women who were free from known cardiovascular disease at the beginning of follow-up between 1984 and 1986. The relative risk of death was calculated as the rate of death among participants within a given physical activity category compared with the rate of death in the reference category (no physical activity). We used Cox regression analysis to adjust for age and other potentially confounding factors.
Results: After 16 years (SD 4 years) of follow-up, 2946 men (10.8%) and 2486 women (8.6%) had died from ischaemic heart disease or stroke. A single weekly bout of exercise of high intensity reduced the risk of cardiovascular death, both in men [relative risk (RR) 0.61, 95% confidence interval (CI) 0.49-0.75], and women (RR 0.49, 95% CI 0.27-0.89), compared with those who reported no activity. There was no additional benefit from increasing the duration or the number of exercise sessions per week. The risk reduction related to exercise increased with increasing age in men, but not in women.
Conclusion: These results challenge the current recommendation that expenditure of at least 1000 kcal per week is required to achieve exercise-induced protection against premature cardiovascular mortality.