Three thousand, five hundred and forty kilometres over 21 days, through four countries, 635 cities and over five mountains with a punishing finish that demands riders complete 222.5 km on Day 19, is park of what makes the Tour de France such a beast of a race.

Who are the 198 cyclists who on most days spend four to six hours on their bikes posting speeds of 45-60 km per hour on the flats and 20 km per hour climbing mountains so high and so steep even the average car labours to reach the summit?

The all-male contingent is predominately Caucasian with an average age of 29 years. Known for their aerobic endurance, cyclists in the Tour post VO2 max scores between 70-80 ml/kg/min (the more oxygen your body delivers to the working muscles, the more power it can produce),which puts them alongside cross-country skiers as the athletes with the most impressive measures of aerobic power. Compare that with the average male couch potato with a VO2 max around 45 ml/per kg/per min and a fit recreational cyclist who boasts about his VO2 max score of 60 ml/per kg/per min and you get a feel for the aerobic fitness of most elite cyclists.

But not all Tour riders are created equal, with some excelling on the flats and others on the climbs. Climbers have the highest VO2max scores, which are closer to 80 ml/kg/min., considered the minimum needed to win the Tour. Chris Froome, winner of the Tour de France three times in the last four years, has a VO2 max that ranges from 80-88 ml/kg/minute (depending on his weight).

Riders at the front of the pack during the time trial stages of the race have powerful bodies built for speed. Winners of the coveted green jersey, given to the best sprinter, typically weigh 70-75 kg (155-165 lbs), are 180-185 cm (around 6ft) tall and have a BMI of 22. Climbers are leaner and about three inches shorter — 175-180 cm in height, 60-66 kg (132-145 lbs) on the scale with a BMI of 19-20, which helps them sustain their speed during tough ascents that typically last 35 to 40 minutes. Going uphill demands an exceptional power to weight ratio, which means winners of the red polka dot jersey, the so-called King of the Mountain, have a lean body that produces impressive amounts of power for an extended period of time.