The moves are effective Jan. 1. Frisk, 56 years old, will report to Plank, who will become executive chairman and brand chief.
Plank founded Under Armour in 1996.
"Our multi-year, transition approach has ensured purposeful leadership continuity. Patrik is the right person to serve as Under Armour's next CEO," said Plank. "As my partner during the most transformative chapter in our history, he has been exceptional in his ability to translate our brand's vision into world-class execution by focusing on our long-term strategy and re-engineering our ecosystem through a strategic, operational and cultural transformation."
Frisk joined Under Armour in 2017 following "nearly 30 years of experience in the apparel, footwear and retail industry," Under Armour said in a statement.
The stock rose 2% to $20.4 in trading Tuesday.
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