New York, United States | 

Sidy Diallo has traveled the globe, sometimes running  marathons in consecutive weeks -- he is running  in New York -- to preach the still largely unappreciated benefits of running barefoot.  

"There's a man without shoes. Watch out for him!," a pedicab driver shakes his head in amazement at the sight of the tall, spindly runner making his way through Central Park.

Having trained for and run 63 marathons barefoot since 2015, Diallo has grown accustomed to the full gamut of reactions, from sympathy to open hostility.

"Insane! He's crazy!" shouted one spectator he passed while running the Chicago Marathon three weeks ago, said the Guinean-born Diallo.

"When people see me like that," he said, "it brings out the animal in them and some get angry... and even aggressive."

Others wince, worried he is in pain or doing damage to his feet. 

"I see the fear on the faces of some people," Diallo says.

There was definitely pain in the early days, he acknowledges. A physician by training who switched careers and is now a French diplomat, he made his first shoeless runs a bit tentatively.

Having taken up running relatively late in life, at 55, he had run 100 marathons -- wearing shoes -- starting in 2010. 

But by the time he turned 60 in 2015, he was craving a new challenge. 

- A price to pay, at first -

"There is a price to pay" in the first painful days of barefoot running, Diallo concedes. "Your feet and legs have to adapt. Your entire body has to get used to it."

Like others before him, Diallo, who posts on Facebook as Dr. Barefoot, has reverted to the stride used by the first humans, for whom running barefoot was a matter of survival, not just fun. 

The 2009 book "Born to Run" by Chris McDougall sparked a mini-revolution in the American running community, inspiring many runners to go minimalist. 

McDougall wrote about a tribe in northern Mexico known as the Tarahumaras whose members could run dozens of miles a day along rugged canyon paths wearing simple sandals cut out of old car tires. 

He taught himself to run as they did -- and as ancient man did -- using a style known as a forefoot strike, in which the ball of the foot lands first, rather than the heel strike used by nearly all shoe-wearing runners. 

"When you run with shoes, the impact with each stride is 100 percent," generally placing great pressure on the heel, Diallo explained. "When you run barefoot, the body naturally cushions the impact," dramatically lessening it.

Several scientific studies have concluded that barefoot running is indeed less traumatizing to the body than the heel-strike running that the cushioned heels of modern sports shoes encourages.

Diallo and McDougall say barefoot running has helped them avoid major injuries. Ira Rohde, president of the New York chapter of the Barefoot Runners Society, agrees. 

- 'You feel good' -

But despite the publicity generated by "Born to Run" and the growing popularity of running in the Western world, barefoot running remains a micro-niche.

"In the USA, the 'fad' phase of barefoot running is certainly long gone," Rohde says. "There remains much more interest in Europe."

Despite posting a notice about his plans to run last Sunday, Rohde was the only person to show up barefoot, under a light drizzle, for his usual run in Central Park. 

Ken Posner, a specialist in barefoot trail-running, says that in 20 years in New York he remembers seeing only seven barefoot runners.  

And in the 80 marathons or ultra-marathons he has run, he has seen only three. 

He attributes this to the weight of social convention.

To run without shoes, he says, you have to be "willing to stand out very visibly from the crowd." 

Patience is also required. "You have to slow down when the ground gets rough, and it seems like most people are in a constant rush."

Still, this author of "Running the Long Path" believes his philosophy will spread, as it has among those already running in lightweight, minimally cushioned shoes designed to be just a step away from running barefoot.  

"A lot of people are starting to do it" and finding it to be surprisingly enjoyable, Diallo says. 

"Imagine yourself walking on a beach of fine sand, or on a lawn. You feel good. It's the same sensation, only super-sized!" 

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