Meanwhile, a number of competitors and new players in the space — both in performance wear and ath-leisure — continue to try to emulate Lululemon's success. Some investors are worried too. The theory is that the stock has risen so much and so fast that it can't get any better and will likely fall soon. Shares of Lululemon are up more than 41 percent year-over-year. More than 350 percent in the last five years.