It’s possible! To be a stronger runner, you are supposed to keep workouts constantly varied, and to do them for time, right?
Same thing as CrossFit. How the runner does this is by doing Fartlek workouts that vary in terrain, duration and speed they are to do it by way of intervals. During the run, nothing is predictable so the body has to constantly strive to adjust, which is more taxing on the muscles and cardiovascular system. The post-calorie burn is also greater since the overall workout is more challenging overall.
One of the workouts I recorded this week for Aaptiv features a Fartlek, CrossFit-esque class. I have the run constantly varied in terms of time and speed, which is a common theme in CrossFit workouts (in regards to the metabolic conditioning aspect of it). The reason for this run is to be able to do (run) whatever duration and speed you are given, at random. It’s important to do this so you don’t plateau and acclimate to any set workout. This improves your overall running economy, and not to mention, can help you lean out as well.