Under Armour is determined to strike a chord with female athletes—many of whom have been buying the brand, but aren’t that emotionally attached to it. The company has kicked off a campaign that includes a Facebook page dedicated to women’s performance apparel. The target demographic is a female consumer who “trains in Under Armour, but doesn’t really know about the brand other than [that] it’s her boyfriend’s brand,” said Adrienne Lofton, senior marketing director of Under Armour’s....