DSW, the American chain retailer, reported a sales increase of 16.5 percent to $449.5 million for the quarter ended May 1. Comparable store sales rose by 16.2 percent. The gross profit margin was 32.8 percent, 5.6 percentage points higher than the first quarter 2009. Operating profit more than quadrupled to $49.1 million, compared with $12.1 million last year. Net income skyrocketed by 322 percent to $30.2 million.

Toning shoes make up about 15 percent of DSW's athletic sales by volume, the company said, and around 3 percent of total volume. So far, growth in that category hasn't cut into the sales of other categories, though the company acknowledges that this could happen in the future, especially as the design of toning shoes becomes more like casual shoes.

The company reiterated its estimate of a 6-8 percent increase in annual comparable store sales for fiscal 2010.