With major 26.2-mile races in Washington, D.C., New York City and Philadelphia coming up this fall, it's safe to say we are in peak marathon season.

According to Running USA, almost two million people ran a half-marathon in the U.S. last year, and more than a quarter of that ran a full. Although down from the previous year's high, the market for running shoes is still showing no signs of slowing down. In 2015, Americans spent $3.2 billion on running shoes, according to the National Sporting Goods Association—up 40% since 2010.

For hardcore runners, smaller brands are still at the forefront when it comes to performance. According to a recent Running USA survey, Brooks is the most recently purchased running shoe brand by serious runners (23%), followed by ASICS and Saucony --- New Balance came in 5th, just behind Nike.

Meanwhile, adidas (arguably this year's most improved brand) isn't even on the radar when it comes to hardcore runners.

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