Lululemon Athletica Inc., the apparel chain with a tech start-up's valuation, as expected told investors its sales grew strongly for the 12th consecutive quarter.

The mystery is how the chain has managed to turn yoga gear into a miniempire, notching a market value of $10.4 billion with sales of just $712 million last year, and whether it can sustain the pace. After all, in the prior quarter, it booked a record $1,800 in sales per square foot—more than three times luxury kingpin Neiman Marcus's sales for its most recent full...