Exercise and haemostatic function.

To reduce the risk of ischaemic heart disease, vigorous exercise has to be maintained over time. This suggests that the benefit is at least partly due to a short-term effect, such as an influence on the haemostatic system and thrombogenic potential. A high plasma fibrinogen level is strongly and independently associated with the incidence of ischaemic heart disease, and the effects of exercise on fibrinogen have now been extensively investigated. One randomized controlled trial and several large epidemiological studies show that vigorous exercise lowers the plasma fibrinogen level by an amount that would reduce the risk of ischaemic heart disease by 7 or 8% on a conservative estimate, along with additional benefits due to any favourable effects on blood pressure and lipids, for example. However, unaccustomed exertion raises the immediate risk of ischaemic heart disease probably, at least in part, through a short-term increase in coagulability. Thus, those who are not accustomed to physical exertion should approach it gradually in the early stages of exercise programmes.