How does cardiovascular health improve through cardio/aerobic exercise? Especially for those with clogged arteries from years of a sedentary lifestyle and poor dietary habits. What does the body do to correct this?

In order to move, your muscles need energy. A key piece in making energy is oxygen (like how you have to blow on a fire to get it to start burning). That oxygen comes from the blood. The blood comes from the heart.

When you exercise, the heart pumps harder. If you keep exercising, the heart gets better at pumping like all the other muscles in your body. With a better pump, you can get more blood with oxygen to the muscles.

But what about the clogged arteries? The blood can’t get there if the arteries are clogged. So your body can literally make new blood vessels to get to the muscles that are working.

These are called collateral vessels if you want to learn more.

In addition to what has already been said. Constant low intensity aerobic exercise can increase the amount of mitochondria in your cells. Mitochondria product the fuel your cells use to do work. So more aerobic exercise -> more mitochondria -> more ability to do work.
Also your muscles will grow more capillaries in them so that more blood can flow. This allows more oxygen to reach your muscles allowing them to do more work.

The last part of your question – your body doesn’t correct clogged arteries. A surgeon goes in there and has to remove blockages if they get really bad. I read that over time, with a high fiber diet, you can reduce the impact of plaque buildup. You don’t really want plaque to break off anyway, it can cause clots where you don’t want them, like in your brain or your heart. The propensity for your arteries to stiffen and collect things on the inside of them is a major design flaw.

Atherogenesis (formation of fat in arteries) starts in the first decade of life. The mechanism of development and how to counteract this is not fully understood. Reducing the level of fat (ldl) has shown to reduce atheroma burden, amongst a few other complicated things.

Exercise is very useful for peripheral arterial disease, lessening symptoms. Keep walking if nothing else!