VAN NUYS, Calif. — Authentic Fitness Corp., whose stock has risen substantially since its initial public offering in June at $14 a share, announced a 2-for-1 split on its common stock, payable Feb. 10 to shareholders of record Jan. 20.

In December the company sold 2 million shares in a secondary offering at 31 1/8 a share. On Monday the firm’s stock closed at 27 1/4 on the New York Stock Exchange, down 1/2.

After the split, there will be 21.3 million shares outstanding, including warrants, stated Linda J. Wachner, chairman and chief executive officer.

Since the IPO, the firm has expanded its swimwear brands with the acquisition of the Cole, Catalina and Ann Cole labels. The firm also is expanding its fitness stores featuring its Speedo brand. It has eight, but 40 more are slated to open this year.