Showing how to create expressions that will loop key-framed animation in After EFfects, Shawn Sheehan demonstrates how to loop a simple run cycle animation over the length of the composition.

In this tutorial, we will learn how to use the loopIn and loopOut expressions to loop keyframed animation

Using two Time Remapping Keyframes, Shawn uses the loopOut and loopIn expressions which will allow you to change the animation without having to render the loop first, and explains a little bit on how the loop expressions will work in After Effects. Check out the tutorial for How to Create a Looping Animation Using Expressions in After Effects here.