...The high average speeds (approximately 45 kph) at which riders are able to cover these stages require that they push high gears (53 X 12 to 11) during long periods. This inevitably results in some muscle damage. Previous research has reported increased levels of muscle damage markers during cycling tour races (Mena, Maynar, and Campillo 1996). This phenomenon may have a negative impact on performance during the second part of a three-week race, during which accumulated muscle fatigue may considerably limit performance in the phases of competition that determine the winner—the time trials and high mountain passes....
http://mytriathlontraining.com/content/cycling-trends-tour-races
http://mytriathlontraining.com/content/cycling-trends-tour-races