I can think of no sporting event in the world that puts requires the level continuous high level endurance performance and recovery involving speed, aerobic and anaerobic performance, strength, and stamina as the Tour de France. The same to a lesser degree on some other bicycle endurance races!
Its hard given the combination of the demands of the race combined with competitiveness of the elite cyclists to imagine that some type of performance enhancing will continue.
Before doping cyclist used steroids and or stimulants such as amphetamine type drugs. The latter sort of stopped when a top cyclist dropped dead on his bike at the top of the most famous climb decades ago.
I wouldnt be surprised to eventually see PED of some types to gradually become legalized and regulated in cycling and professional sports in general such as the NFL.
The hard truth is if it turns out you can't stop it then you need to control and regulate it. I'm not saying I like it I'm just expressing an analysis of the issues.
Here is how doping works as far as benefits and risks. (It increases the number level of oxygen that ones blood can carry.) Frankly the risks though real are in the big picture considering the target group combined with some safety measures that could be mandated and to be honest the risks are not that serious.
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www.webmd.com/fitness-ex ··· d-doping