BALTIMORE, United States — Early Under Armour Inc. executive Kip Fulks is stepping away from the athletic brand, which is trying to restore sputtering sales growth, according to a person familiar with the situation.

Fulks is taking a sabbatical, said the person, who asked not to be identified because the move isn't public. The Wall Street Journal, which previously reported on Fulks's departure, said the company also is considering exiting some categories, including tennis and fishing, as part of a shake-up.

The news fuelled concern that Under Armour is in disarray, sending the shares down as much as 3.9 percent to $16.80 on Monday. The stock has lost more than half its value in the past year.

The company is reeling from sluggish sales in North America, where heavy competition with Nike Inc. and Adidas AG is hampering growth. Under Armour cut its annual forecast in August after posting its second straight quarterly loss.

Chief executive Kevin Plank, 45, aims to rely less on the North American market by expanding overseas, but the effort is taking time to pay off. Only about a fifth of Under Armour's sales currently come from overseas.

Fulks has held a variety of roles and was once Plank’s second in command. More recently, he has served as a strategic adviser.

Fulks didn’t immediately respond to a request for comment.

By Matt Townsend; Editors: Nick Turner, Lisa Wolfson.