Plank added that when the U.S. speedskating team performed below expectations, there were only "so many variables," to explain the disappointment, and the new suit was one possibility. He added that Under Armour athletes have won 10 medals at the Olympics.
In addition to U.S. speedskating, Under Armour has exclusive uniform agreements with the U.S. bobsled and skeleton teams, U.S. gymnastics and the Canadian snowboarding team.
Under Armour shares rose $4.19, or 3.9 percent, to $111.38 in morning trading after hitting an all-time high of $111.97 earlier in the session. The stock is up more than 22 percent so far this year.
AP Sports Writer Beth Harris in Sochi, Russia, contributed to this report.