Physics of Running?

What is the Physics behind Running?
The actual physics.

Does it has to do something with your legs being pendulums moving back and forth. Or the simple machines that make the leg up and Newtons action and reaction 3rd law along with gravity.

But I cannot find many links on the internet about this subject. Some help is appreciated.

Has to do with the way your muscles contract, springing you forwards. Common sense really.

Here are a couple sites with some biomechanical analyses of running:

It’s a pendulum action, but don’t forget the arms