Article from Guardian newspaper from last year
http://www.guardian.co.uk/sport/blog/2012/jul/10/tour-mountains-science-of-sport - some choice quotes:
Slower tour times bring things back into the realms of expected physiology.
When a rider produces performances that have "alien" physiology implications, it's a strong flag for doping
The "abnormal" physiology of years gone by came from guys who were sustaining 6.4W/kg for 45 minutes. That points to a human that has a VO2max of 97 ml/kg/min on the bike, or an efficiency of 28%, or can sustain 95% of max for 45 min at the end of five hours of racing. That just doesn't happen.
Can't find doping article this year in the Grauniad ...