The term triple extension refers to the simultaneous extension of the hips, knees, and ankles. This happens during the push-off phase in running. Performing this motion through triple extension exercises can help to clean up your running form and build power, for a more efficient stride. Here are two options to try- one with equipment, and one without. 

The first option is to perform a squat to calf raise. Since the extension part of this exercise is what is important, don’t worry about squatting very deep. Begin by squatting about halfway down, then drive through your heels and extend your ankles, knees, and hips until you are in a standing calf raise. Drive your elbows back as you extend forward. If you are comfortable with this exercise and want to add challenge, you can perform a squat jump for added plyometric benefit.

The second option is the banded triple extension. Loop a resistance band around your waist and around a very sturdy object (think a squat rack), or you can have a friend hold the other end of the band. Then drive one of your knees forward, while extending your ankle, knee, and hip on the other side. Move your arms in sync with your legs, as in a running motion. If you want more challenge, move further away from the sturdy object during the start phase or use a heavier resistance band. If you have a durable object that is about knee height, place it a few feet in front of you to use as a target for the leg that is driving forward to step on at the end of the exercise. Only perform the added challenge if you are confident you can do so without hurting yourself - the basic exercise will still give you plenty of benefit!