The desire to "look active" is helping to drive sales of athletic footwear and activewear in the US, new research suggests.

Total sales of US athletic footwear and activewear reached US$36bn between January and August - up 4% on the same period last year, NPD Group's Consumer Tracking Service found.

Activewear sales increased more than the general apparel market - up 7% and 1% respectively, compared to the prior-year period. Units rose 7%, while the average selling price was flat.

"Part of the reason activewear products are growing faster than the overall business is attributed to the consumer's passion to get more fit," said Marshal Cohen, chief industry analyst at The NPD Group.

"But the major influence on the rise in sales, especially in women's, is the desire to look active."

Women's contributed 5% or $7bn in sales to the activewear market, with gains in sales of active pants - up 10%, tees/athletic tops - rising 12%, and sweatshirts - up 11%.

"As dressing casually becomes more acceptable, women feel they are getting value when investing in activewear, like yoga pants, which they can wear to the gym, in the gym, and from the gym," Cohen added.

Meanwhile, athletic footwear sales edged up 1% during the period, but units and average selling price were "relatively flat". Men's had the largest share of the market with 51%.

Growth was driven by men's running footwear - owning a 24% share of the market - as well as more fashion categories. Casual athletics was up 6% with a 26% share, and basketball footwear grew 12% with an 11% share.

"Contrary to the women's trend in activewear, young men have found the desire to dress up by wearing a suit with athletic shoes. This look is also becoming popular among the middle-aged male market seeking that active look," added Cohen.

"So in athletic footwear, consumers are keeping with the multiple uses trend and buying footwear to match their activewear as well as their dinner outfit."