Under Armour founder sold $138 million in stock during time period company allegedly misled investors about slowing sales

Kevin Plank gushed about his business on a call with Wall Street analysts in October 2015.

Under Armour, the sports apparel maker Plank founded two decades earlier in the basement of his grandmother's D.C. townhouse, had grown into a global juggernaut, he said, securing endorsements with some of the world's biggest sports stars, amassing data on millions…