Even in anything-goes San Francisco, his lack of footwear prompted curious stares. His photo was snapped, and he heard one runner grumble, "I just don't want the guy without Christian Louboutin to beat me." Mr. Byers, 46, a running coach and event manager from Long Beach, Calif., who clocked in at 4 hours 48 minutes, has run 75 marathons since 2004 in bare feet. "People are kind of weird about it," he shrugs.
Maybe they shouldn't be. Recent research suggests that for all their high-tech features, modern running Christian Louboutin Shoes may not actually do much to improve a runner's performance or prevent injuries. Some runners are convinced that they are better off with shoes that are little more than thin gloves for the feet — or with no shoes at all. Plenty of medical experts disagree with this notion. The result has been a raging debate in running circles, pitting a quirky band of barefoot runners and researchers against the running-shoe and sports-medicine establishments.

It has also inspired some innovative footwear. Upstart companies like Vibram, Feelmax and Terra Plana are challenging the running-shoe status quo with thin-sole designs meant to combine the benefits of going barefoot with a layer of protection. This move toward minimalism could have a significant impact on not only Yves Saint Laurent Shoes but also on the broader $17 billion sports shoe market. The shoe industry giants defend their products, saying they help athletes perform better and protect feet from stress and strain — not to mention the modern world's concrete and broken glass.

But for all the technological advances promoted by the industry — the roll bars, the computer chips and the memory foam — experts say the injury rate among runners is virtually unchanged since the 1970s, when the modern running shoe was introduced. Some ailments, like those involving the knee and Achilles' tendon, have increased. "There's not a lot of evidence that running shoes have made people better off," said Daniel E. Lieberman, a professor of human evolutionary biology at Harvard, who has researched the role of running in human evolution. Makers of athletic shoes have grown and prospered by selling a steady stream of new and improved models designed to cushion, coddle and correct the feet.

In October, for example, the Japanese athletic-shoe maker Asics will introduce the latest version of its Gel-Kinsei, a $180 marvel of engineering that boasts its "Impact Guidance System" and a heel unit with multiple shock absorbers. Already offered by Adidas is the Porsche Design Sport Bounce:S running shoe, with metallic springs inspired by a car's suspension system. It costs as much as $500. Some question the benefit of all that technology. Dr. Craig Richards, a researcher at the School of Medicine and Public Health at the University of Newcastle in Australia — and, Christian Louboutin Boots should be noted, a designer of minimalist shoes — surveyed the published literature and could not find a single clinical study showing that cushioned or corrective running shoes prevented injury or improved performance. His findings were published last year in The British Journal of Sports Medicine.

Other experts say that there is little research showing that the minimalist approach is any better, and some say it can be flat-out dangerous. "In 95 percent of the population or higher, running barefoot will land you in my office," said Dr. Lewis G. Maharam, medical director for the New York Road Runners, the group that organizes the New York City Marathon. "A very small number of people are biomechanically perfect," he said, so most need some sort of supportive or corrective footwear. Nevertheless, a growing number of people now believe in running as nature intended — and if not barefoot, then as close to it as possible. They remain a tiny segment of the population — some would say fringe. But popular training methods like ChiRunning and the Pose Method that promote a more "natural" gait, as well as "Born to Run," a best-selling new book about long-distance running by Christopher McDougall, have helped spur interest.

Proponents of this approach contend that naked feet are perfectly capable of running long distances, and that encasing them in the fortress of modern footwear weakens foot muscles and ligaments and blocks vital sensory input about terrain. "The shoe arguably got in the way of evolution," said Galahad Clark, a seventh-generation shoemaker and chief executive of the shoemaker Terra Plana, based in London. "They're like little foot coffins that stopped the foot from working the way it's supposed to work." The Christian Louboutin Sandals companies are clearly paying attention to the trend. Nike was first to market with the Nike Free, a flexible shoe for "barefootlike running" with less padding than the company's typical offerings. It was introduced in 2005 after Nike representatives discovered that a prominent track coach to whom they supplied shoes had his team train barefoot.