Spit in one hand, want in the other, see which one fills up first.

My ex mother-in-law used to say that all the time and I never really understood what it meant. But now, I think I get it, we want spectacular entertainment in the Tour de France, but we want the riders to be clean.

We want one amazing rider to fly up the climb and destroy the field, effortlessly dancing on the pedals while the others look amateur.

Well, guess what? Mick Jagger said it right: you can’t always get what you want.

I for, one, was enthralled by the duel on the Tourmalet. After reading a wonderfully presented article by two passionate physiologists, I was even more satisfied – it seems that science has shown that the riders are likely to be clean.

Hooray! They’re tiring! They can’t accelerate like motorbikes up a 10% climb after 17 days in the saddle (we still loathe you, Ricardo Ricco, in case you’re wondering) and they sure as hell don’t seem to be doing anything ‘superhuman’ anymore.

Dr Ross Tucker and Dr Jonathan Dugas of Science in Sport have long been commentating on the how’s and why’s of performance, and their latest article on the power output from the Tourmalet is fascinating.

In summary, it explains that the power generated by the best men in the field is commensurate with a much more plausible capability, something Dr Tucker calls “physiologically believable.”

It reveals that the tour is slower than before, especially in the all-important mountain stages where drafting and tactics are less at play (on the Tourmalet, there appeared to be one tactic: ride as hard as you can).

Both the climbing times are slower and the power outputs of key riders are down, which can be in part due to the anti-doping measures and the stringent application of the biological passport.

Reassuringly, though, motivation is not impaired. For those with an objective, all kinds of physical and mental fatigue can be ignored, if only for a day.

We saw Contador and Schleck’s face off on the climb, but equally impressive are the displays of strength and endurance seen by the sprinters’ teams in stage 18.

After reading Michael Rogers’ blog, I felt I could sympathise with the HTC-Columbia rider (if only in a miniscule way – the Giro Donne is only 10 days!) The Australian came to this Tour with hopes of a top-five finish, but has been losing minutes every day.

Rogers was a three-time world champion in the time trial (2003-5), and is a consistent tour rider. But in 2008, he crashed out of the Tour while he was the virtual maillot jaune and in 2009 was recovering from glandular fever.

He wrote yesterday that on every twist and turn of the road before the Tourmalet, he was struggling to stay in contact with the peloton. The wheel in front seemed eternally too far away.

And yet with the mountains done, and his favourite discipline still to come (stage 19 is a 52km time trial), he had to rally.

There was just the small matter of driving the lead-out train with teammates Tony Martin and Bernard Eisel for Cavendish to get his third stage victory. And what a train they drove!

The camera would focus on the speed of the motorbike: 60km/h for the last 28km of the 200km stage, showing the peloton strung out in single file for the final 10km.

These HTC-Columbia’s guys were no less tired than everyone else, but with the incentive of pride, money, fame … maybe the chance to get Cavendish blubbering on the podium again (I mean, really!), they were capable of unreasonable things.

I thought of how tired Rogers must be, looked at his legs and his face as he led 171 tired men, making them suffer, and was reminded that if it must be done, it will be done.

(Bridie O'Donnell is an Australian professional rider with UCI Team Valdarno and divides her year between Tuscany and Melbourne. She is Back Page Lead's cycling columnist - and editor of her own blog, Bridie.com.au.)