Walking or cycling for 20 minutes a day can reduce a 60-year-old man's risk of heart failure by a fifth, a study has found.
Researchers who monitored the progress of 33,000 Swedish men from 1998 to 2012 found that the least physically active were most likely to develop heart failure.
The condition occurs when the heart becomes too weak to pump sufficient blood around the body.
Analysis of the most beneficial forms of activity showed that walking or cycling for 20 minutes a day was associated with the biggest risk reduction. It was more protective than heavy-duty exercise.
The men, who had an average age of 60, filled out a questionnaire asking them about their levels of exercise the previous year. They also recalled how active they were at the age of 30.
The research showed that recent active behaviour had a bigger impact on heart failure risk than activity earlier in life.
Study author Andrea Bellavia, from the Karolinska Institute in Stockholm, said: "Because participants in the study cohort had also provided information about their physical activity at age 30, as well as at the time of enrolment around age 60, we were able to examine the long-term impacts of physical activity on heart failure.
"We found that recent activity may be more important for heart failure protection than past physical activity levels. The first incidence of heart failure in men was also later for those who actively walked or bicycled 20 minutes each day."
The research, published in the Journal of the American College of Cardiology: Heart Failure, suggests that compared with moderate exercise levels, both too little and too much activity increase the relative risk of the condition.
"The U-shaped relationship between exercise levels and the likelihood of subsequent heart failure is a unique finding and will stimulate further research in the important field of prevention," said Dr Christopher O'Connor, the journal's editor-in-chief.