There are two rules for racewalking. Official races are judged and you must obey these rules.
(1) Your knee must be straight when your foot strikes the ground and remain straight until your body passes over that foot.
(2) One foot must be on the ground at all times when walking.
Violating the 1st rule is called "creeping" and violating the 2nd is called "lifting." Don't break the rules unless you want to go walking home in defeat.