People often celebrate the quads and glutes as the powerhouse muscles for running. But go a little farther down the kinetic chain and you’ll find the true unsung heroes: your calves.

The calf complex includes two different muscles: the gastrocnemius (bigger, upper calf muscle) and the soleus (smaller, deeper calf muscle). When you run, the gastroc and soleus put in “tremendous work” with every single stride, helping to absorb impact and literally propel you forward, Leada Malek, PT, DPT , a physical therapist and author of The Science of Stretch , tells Runner’s World.

In fact, if you think about it, running is really just a bunch of single-leg hops—an action that requires a bunch of power to get your entire body off the floor, Carla Foster, PT, DPT , a physical therapist with Mims Method PT in New York City, tells Runner’s World.…