LANNEMEZAN, France (AFP) - While the battle for the yellow jersey should be dominating thoughts ahead of Thursday's final Pyrenean stage, it has been doping, the heat and even Lance Armstrong hogging attention at the Tour de France.

After two baking hot days in the mountains in which several riders - including Alberto Contador and Vincenzo Nibali - complained of being unable to breath, Thursday's 195km stage 12 promises to be even hotter and harder.

The peloton has been feeling the strain, losing already 21 riders and with more than half of the remainder already more than an hour behind Froome.

The 30-year-old Briton has not been having an easy time , at least off-course.

Following his stage 10 victory on Tuesday, he had to bat away questions about doping.

The Team Sky leader has remained calm but did demand more respect, claiming people should show some "proof before... making accusations".

The Tour cannot escape from Armstrong's dark shadow, though.

The American is taking part in a charity ride to raise money for leukaemia sufferers.

The ride, organised by former England international footballer Geoff Thomas' charitable foundation, covers each Tour stage a day before it happens.

Armstrong was due to ride the 13th and 14th stages on Thursday and Friday but Froome dismissed it as a sideshow.

"I wish Geoff Thomas and the guys all the best in raising as much money as they can. (But Armstrong) is not on the line with us here, we're not going to see him, it's a non-event for us."