Kevin Plank, Under Armour’s Founder, Will Return as C.E.O.

Under Armour, the sports apparel company, said on Wednesday that its founder, Kevin Plank, would return as chief executive, in a leadership shake-up that will seek to revitalize the struggling brand.

Mr. Plank, who founded Under Armour in 1996, had remained the company’s executive chair and controlling shareholder after exiting as chief executive at the end of 2019. He will take over on April 1 from Stephanie Linnartz, who led the company for just over a year. Ms. Linnartz took over from Patrik Frisk, who served in that role for two years.

Under Armour, once hyped as the next Nike, has faltered in recent years amid a series of missteps and shifting consumer tastes in a highly competitive market. With sales slumping, the company’s stock has fallen by about 85 percent since reaching a record high in 2015. It rose slightly in after-hours trading after the news that Mr. Plank would be returning to lead the company after four years away from the job.

In a note to employees posted on LinkedIn announcing his return, Mr. Plank said that the company was assessing its direction in an effort to “help us make the right choices to put us back on a path to actively build and drive toward our full brand potential.”

Ms. Linnartz, who made a series of personnel changes in the company’s leadership team in recent months, has spoken lately about jumping on the booming interest in athleisure with new marketing and products. In a post on LinkedIn announcing her departure Wednesday, she spoke positively about her time at Under Armour. She will continue to advise the company until the end of April.

Mohamed El-Erian, the economist and former chief executive of the investment management giant Pimco, will now be the board chair.

Amanda Miller, a spokeswoman for Under Armour, declined to comment on the reason for the leadership change and who was behind the decision. Mr. Plank and Ms. Linnartz did not immediately return requests for additional comment on Wednesday evening.

Mr. Plank’s first stint as chief executive was not without controversy. In May 2021, the company paid $9 million to settle charges brought by the Securities and Exchange Commission that it had misled investors about its sales growth in the mid-2010s.