A tiny 25-year-old Colombian rider with a freakish VO2 max has the world's best cyclists terrified going into the Tour de France

The world's premier bicycle race, the Tour de France, starts July 4, and there are four big favorites to win it.

Three of them have won the Tour before: Spain's Alberto Contador, in 2007 and 2009; Kenyan-born UK rider Chris Froome, in 2013; and Italy's Vincezno Nibali, the defending champion.

The fourth favorite has never won the race: Colombia's Nairo Quintana. But for many he's still the man to beat, which is remarkable considering it's only his fifth time riding a grand tour, or three-week stage race.

The Tour de France route changes every year, and this time there is only one individual time trial, and it's just 13.8 kilometers long. Nairo is a pretty good time-trial rider, but he would more than likely lose valuable time against the likes of Froome and Contador if the ITT were longer. Good for him it's not.

The only other TT is a team time trial, and Quintana's Movistar Team is strong in that discipline, so he shouldn't lose much time, if any, there. So most of the Tour should come down to the battles in the high mountains, which bodes well for the compact Colombian and not so well for his chief rivals, who are great climbers but essentially more all-rounders than climbing specialists.

Who is Nairo Quintana?

While many may not know the name Quintana as well as they do, say, Froome or Contador, the quiet Colombian has made his mark in pro cycling over the past few years, and he's now very much a marked man in the peloton.

Nairo Alexánder Quintana Rojas, 25, is a climbing specialist on the Spanish Movistar Team. At five-seven and 130 pounds, he goes up mountains faster than just about anyone, and that makes his rivals nervous. He has shown in previous races that on the steepest gradients he can attack, attack, and attack again until he drops everyone.

Last year he became the first South American to win the Tour of Italy, or Giro d'Italia, the second most prestigious stage race after the Tour.

And he finished second in his very first Tour de France, in 2013, to Froome. (Quintana skipped the Tour last year after winning the Giro.) That was the highest place a South American rider had ever finished in the Tour.

This year Quintana looks to go up a step on the podium and win, and make more history for Columbia as its first Tour champion.

Physically, Quintana is just very tough to beat. As The Wall Street Journal reported (emphasis added):

Quintana's VO2 max, a key performance indicator that measures the maximum amount of oxygen an athlete can use. Elite cyclists often register a VO2 max in the 60s or 70s. Quintana scored an 86, about the same as [Lance] Armstrong, who won the Tour de France seven times before being stripped of those titles for doping.

The unassuming Quintana has a background that's vastly different from that of his rivals in pro cycling, a sport that's been dominated by Europeans for a century.

As NPR reports, Quintana was raised on a farm 10,000 feet high in the Andes near the village of Cómbita. As a toddler, he nearly died from a bad case of diarrhea. Growing up, he would not play sports but helped his dad out with the farm and did his chores, often getting up at 2 a.m.

According to the Colombian cycling blog Alps & Andes, Quintana was raised by peasant parents in "precariously difficult economic conditions," and yet it was those challenging times that helped bring cycling into his life. His family got him a bike so that he could travel to the nearest school, which was nine miles away.

From Alps & Andes on Quintana's introduction to cycling:

His father bought a used mountain bike for the equivalent of $30. Nairo treasured the bike, and slowly began to daydream during his rides to school. Every time he rode the bike, he pictured himself racing, and winning a stage that always ended on a mountaintop (which was actually his home), after a lengthy 8% climb. Once there, his parents were always there to greet him when he arrived.

NPR also notes that as a high-schooler Quintana grew so strong as a rider that he'd sometimes attach a cable to his sister's bike and tow her up hills. He'd go on to win his first races on a secondhand bike, and the rest is history.

Asked two years ago about winning the Tour de France one day, the ever chill Quintana just said, it's possible.

Now Quintana, 25, finds himself a five-star favorite. Not bad for someone who didn't even play sports as a kid. In the coming three weeks we'll see how he fares against the world's best.