The Grand Tours of cycling – the three-week races of Italy, France and Spain – have no sporting rivals as feats of endurance. The Tour de France, the oldest and grandest of them all, offers a particularly searching examination of a rider’s physical fitness and mental resilience.

Ferocious climbs, nerve-shredding descents, full-bore sprints and timed efforts that require nothing less from a rider than that he ride to exhaustion. All cycling life is here, almost every day, for three weeks. Just two rest days are granted among the Tour’s 21 stages, yet most riders choose to spend these in the saddle.

Photo by: Gruber Images

There is a reason that the Tour de France stands alone as a test of endurance; why it shares the rarefied terrain occupied by events that transcend their sport. Bradley Wiggins, Tour winner in 2012, once described it as the only sporting event long enough to require a haircut at the midpoint.

A statistical analysis of cycling’s greatest race offers some insight into the suffering of the riders. Many might blanch at a motoring tour in excess of 3,000 kilometers, never mind cycling such a distance. France’s magnificent mountain ranges always feature, and the mighty Col du Tourmalet, the climb visited more often than any other, once again features this year.

The endurance effort is met by an equal and concomitant demand for performance. There is no collective slacking off as the race wears on. Rather, any reduction in the performance of a competitor is seized upon as an advantage. Tire at your peril; your rivals will sense and ruthlessly exploit it.

Photo by: Gruber Images

The demands of the Tour are not only felt by the riders, but on their clothing and equipment too. It is a searching examination of the materials placed at a team’s disposal, as well as of the riders. Cycling’s ever-increasing focus on aerodynamics has placed added significance on the performance of the clothing. The rider makes up 80 per cent of the aerodynamic picture. Reduce resistance around his silhouette and the gains will be greater than from any yielded by frame or wheels.

When the riders arrive in Paris, it will be the end of a three-week ordeal for many. Even to finish the Tour is an accomplishment: the ride onto the Champs Élysées is a triumphant moment for all who make it that far.

Vive le Tour then, and chapeau to any rider who finishes it. This enthralling, beguiling, debilitating rendezvous with suffering each July is the only place to be for a professional cyclist. The rest of us can only watch and wonder.