Shares of Under Armour jumped Thursday after the company beat earnings expectations, but Morningstar equity analyst Paul Swinand said he remains wary of the company's costs and efficiency.
Swinand said that a review of UA's earnings over the past three years shows operating margin has trailed revenues while share count has grown.
"While the company is doing very well, their operating margin has actually gone down over the last three years," he told CNBC's "Squawk Box." He was wearing Under Armour workout garb during the interview.
"I'm a fan of the company. I like that Kevin is making a big bet on connected fitness, too, but they're also spending a lot to do that. Operating margin is down. That's got to pick up at some point," he said, referring to CEO Kevin Plank.