Getting a toehold in a crowded market. (Sheri Poe, Ryka Inc.) (Risk for Entrepreneurs: The Triumphs and Troubles - of Growing a Business)

Sheri Poe targeted a niche with her aerobic shoes for women. Her biggest challenge now is getting female jocks to know a Ryka from a Reebok

Sheri Poe is the driving force behind Ryka, Inc., a four-year-old company that is churning out women's athletic shoes as fast as it can make them. Although Ryka (pronounced Rye-kuh) is a small player in the $11 billion athletic-shoe industry, it has been an innovator in product design since it was founded in 1987. The Weymouth, Massachusetts, company has sold more than 700,000 pairs of shoes since it brought them to market in 1988.

Competing in the crowded athletic-shoe industry takes some fancy footwork. Long dominated by major players like Nike and Reebok, the market leaves little room for small upstart companies. However, entrepreneurs who identify a market niche and fill it with an innovative product stand a good chance for success.

Poe's idea for a high-performance athletic shoe took wing several years ago when she experienced severe back pain from aerobic workouts. Her discomfort, she realized, was caused by her athletic shoes. "I tried every shoe on the market but none gave me proper support," says the 37-year-old.

While talking to store …