If you’re consistently training, staying healthy, and improving year after year, you may not need major changes to your running form. But when you’re chasing bigger goals—a PR, a Boston qualifier, or simply another level of performance—small details begin to matter more. At higher speeds and longer distances, even subtle inefficiencies can drain energy and make it harder to sustain pace late in a race. The goal at this level isn’t to rebuild your stride. It’s to refine what already works and improve efficiency without sacrificing consistency or durability. With the help of clinical exercise physiologist Heather Milton, The Runner’s World Guide to Running Form is here to help fine-tune every runner’s stride—even those who have been earning postrace medals for decades.…