How does exercise reduce the risk of cardiovascular disease?

Why does exercise reduce the risk of cardiovascular disease? That's an excellent question. We know from multiple very, very large studies involving hundreds of thousands of people over many years, we know that higher levels of physical activity and exercise are associated with a much smaller risk of developing heart attack, stroke or other forms of cardiovascular disease. The mechanisms which are in play when we exercise are numerous, and so there's not one overall one that results in that reduced risk. But some of the things we know are that exercise improves the function of the blood vessels and how well blood flows through them. It reduces the progression of fatty deposits building up in the arteries, and where there are fatty deposits already, exercise helps stabilize those fatty deposits and stop them from breaking apart and causing strokes or heart attacks. If unfortunately someone were to have a heart attack, if they had a history of doing exercise, there is a chance that, strong chance, that by exercising they've already trained their heart muscle to be less likely suffer extensive damage as a result of a heart attack. And the heart muscle itself when you exercise is being pushed to work harder and therefore when it's resting would require less oxygen and therefore it has a lot more reserve to deal with periods of higher need and more work. We also know that exercise is associated with a reduced risk of forming blood clots which obviously are one of the causative factors of a heart attack or a stroke.