When race walking with any form approximating proper technique, the first muscle group to feel in need of a stretch is the shins. Your shin muscles are taxed more in walking than in almost any other sport. In fact, I found that the only athletes who begin race walking with previously developed shins are equestrians. The way their feet sit in the stirrups gives them a special immunity to the early shin discomfort found by many race walkers.
Since race walking forces you to land on your heel with toe pointed, it strains your shin. The body is clearly unaccustomed to this work and reacts by communicating its displeasure. Good stretching helps combat the discomfort. Both shin stretches below provide excellent benefits after walking and can also be executed while working out if your shins begin to burn or become otherwise bothersome.
When your shins hurt, you will find it almost impossible to walk with your toe pointed at heel strike and achieve a proper roll through to your toes. If your shins bother you enough, they may lead you to land flat footed. Most flat-footed walkers have difficulty straightening their knees and must stretch their shins or get themselves disqualified. Enough said?