Lululemon Athletica’s shares spiked Friday after the company’s CEO Calvin McDonald announced his resignation amid declining US sales , with its founder putting the board on notice about a potential proxy battle.

After seven years at the helm, McDonald is stepping down on Jan. 31 and will remain as an advisor to the company through March, he said on a Thursday earnings call discussing two straight quarters of decreasing North America sales.

“We agreed that the timing is right for a change,” McDonald said of his discussions with the company’s board of directors, which is initiating a search for his successor.

Shares of the Vancouver-based athleisure company rose in Thursday’s after-hours trading and were up about 10% to $208 as of Friday afternoon.

The leadership shake-up didn’t come f

See Full Page