Doping

They concealed it about their person, and anecdotally a condom up the bum is best, then produced it when required in anti-doping.

It's been around for years and years. Michel Pollentier was ejected from the Tour in 1978 whilst wearing the yellow jersey for attempting to use someone else's urine, held in a condom under his armpit, when dope tested.

Freddy Martens (who rode on the same team as Pollentier) referred to recatherising in his book in an oblique way, writing how he dealt with an unexpected dope test using a 'particularly painful method', IIRC.