When Steve realized that Barry wasn't moving at a 'normal' speed, he stepped next to him, catching him as he stumbled. Better that he hit him than one of the other patrons or the people of Tombstone seeing something they shouldn't. At least with so much dust around, people might not notice the condition of Barry's shoes.

Instead of commenting on it being 'dumb', Steve just quirked an eyebrow at Barry. "Is being in a movie better than being in the comics?"