You can run 26.2 miles in just about every way imaginable, from blistering fast to slow and steady with a few walk breaks along the way. No matter your pace, your body is working hard , and covering that kind of distance is a massive feat in and of itself.

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But there are big differences in your cardiovascular, metabolic, muscular, and psychological systems when you run a hard pace and finish a marathon in record time versus running an easy pace and taking longer to cover the course. Comparing the two, and using elites as examples, here’s what’s happening under the hood. Plus, what you can learn from the physiology of pros for your own training to run a faster marathon .

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The Cardiovascular System

The Metabolic System

The Muscular System

Psychology

The Cardiovascular System

Running a fast marathon pushes your cardiovascular system into overdrive.…