Richie Porte and Geraint Thomas, two of the top five contenders at the time, quit the Tour de France in pieces after crashing on wet and slippery descents.

Both suffered a broken collarbone, while Australian Porte also fractured his pelvis.

Three more riders quit the Tour after crashes on Sunday's brutal ninth stage while Poland's Rafal Majka made it to the end but then announced on Monday's rest day he would take no further part.

The numerous and often dramatic spills have sparked a debate about whether the Tour's mountain descents are too hazardous.

Dan Martin, who crashed twice on Sunday's final descent of the Mont du Chat climb, suggested organisers ASO are more concerned with the beauty of the race and putting on a spectacle than riders' safety.

"They got what they wanted," after that costly ninth stage, he said.

Nairo Quintana, three times a podium finisher on the Tour, says the descents are simply too dangerous.

"It's not enough of a spectacle to see us on the edge of life at more than 190 beats a minute on the climbs, (now also) on dangerous descents where crashes happen every day," complained the 27-year-old Colombian.

"We lost a team-mate (Alejandro Valverde) in a crash. Sunday was difficult with those of Porte and Thomas, who fell four times (during the Tour) -- I hope they'll recover.

"I have a message to the organisers so that they think about the cyclists.

"They care more about the spectacle than thinking about the life of the cyclist.

"It's not just that they're getting hurt, you're leaving your life out there.

"There are many crashes because of this.

"In Sunday's stage I escaped a crash which could have been one of the worst in my career."

Two-time former Tour winner Alberto Contador was another who had a spill on Sunday.

But the veteran has seen it all before and reacted more soberly than Quintana, pointing out that the problem on the descents was humidity due to rainfall rather than the slopes themselves.

"The slopes are the same as ever, although the rain makes them more difficult," said Contador.

"But I don't think it's necessary to question the course."

- 'Difficult and dangerous' -

Italian Fabio Aru agreed, saying it's all about the rain.

"It wasn't a question (on Sunday) of the stage being dangerous or riders taking risks, but when it rains for the first time in a long time, it becomes difficult and dangerous."

At Grand Tours, much of the focus is on the mountain stages and the battle on the highest and steepest slopes, because that is often where Tours are won and lost.

But descending is every part as much of a rider's skill set as ascending, as race leader and reigning champion Chris Froome pointed out.

"I don't specifically train for descents but we do a lot of training in the mountains and every time you go up a climb, you have to come back down it," he said before the Tour.

Froome himself made a daring break on a descent on the eighth stage last year to put some time into his rivals.

And on Sunday, Romain Bardet nearly pulled off a great escape on a downhill section before being caught by a four-man team, including Froome and Aru, on a flat drag to the finish.

Descents can be spectacular and fascinating but descending is often an ignored skill, according to former rider and now team manager for Directe Energie, Jean-Rene Bernaudeau.

"You need to use a better position to gain two or three kilometres an hour," he said.

"It's free, it doesn't cost you any energy and so you can get a lot of benefit from it."

He added: "You can't learn it, you're either born it or you're not."

For Belgian former world champion Philippe Gilbert, "you have to have a sense of the trajectory, the right material and confidence".

But he added: "Many riders don't know how to descend and don't get any better despite years of practice, sometimes that's a problem."

Source: AFP