Let’s start by examining the first half of the definition, for a moment excluding the words “to the human eye.” A race walker must strike the ground with the leading foot before the rear foot breaks contact with the ground. For a brief moment—the double support phase—both feet remain in contact with the ground.
The photographs below demonstrate race walkers achieving the double support phase at national championship races: proof that walking fast while maintaining constant contact with the ground is possible.
Once referred to as textbook form, today such technique is nearly impossible to find among elite race walkers. Indeed, I sifted through thousands of elite walkers’ photos to find just a few with double contact—and found these only because my collection includes shots from longer races of two hours or more. At longer distances, race walkers naturally use a slower pace, increasing the likelihood of the double support phase.