I was
struck by the vehemance of the current anti-Froome accusations. So I thought I
would add my tuppence worth to this story. First let me nail my colours to the
mast. I have a lot of sympathy with Sir Dave Brailsford when he says “"It is not possible to prove a negative. I
can't," [1].
Sir Dave is referring to the well-known fallacy in
formal logic known as an argumentum ad ignorantiam or “appeal to
ignorance”. This poses that “something is true only because it has not been
proved false, or that something is false only because it has not been proved
true”.
Now there
are some cases where versions of this argument are used by philosophers
(inductive logic relies on it in part). Indeed you cannot prove any future
event true or false until it has happened. Prehistoric man with no knowledge of
physics or astronomy had no definite “proof” that the sun would rise tomorrow
or that walking off a cliff would result in a fatal fall. However, enough
evidence had accumulated from previous life experiences to make these perfectly
reasonable assumptions. Indeed it would be impossible for us to live our lives
without making these kind of inductive “leaps of faith” every day.
Something
ought to go without saying given the scientific literature, but clearly it
needs repeating ad infinitum. Doping allegations based purely on performance
(in this case speed or power data) fall well short of the strong evidence
required for inductive reasoning. Power/time data alone can never prove someone
is doping, or even make it probable. If you doubt this please take time to read
carefully the recent article by Hein FM
Lodewijkx “The Epo Fable in Professional Cycling: Facts, Fallacies and
Fabrications” [2].
Not that
the Lodewijkx review does not prove that epo does not improve performance; in fact it
is careful not to say this. Times have continually
improved in the Tour and doping could be one of many factors that can affect racing
times. The devil is in the scientific detail. But it does make salutary reading
for people who assume that numbers alone are a reason for crying foul.
One thing that is needed is a proper randomized trail in elite cyclists
testing whether epo doping “works”. Crucially, it should include accounting for
the likely strong placebo effect (as everyone “knows” epo works – see my
previous blog). The definitive study would include giving cyclists epo when
they were told they were getting placebo. This kind of approach has been very successful
in studies comparing drug and placebo effects on performance following caffeine
administration [3]. However, significant ethical issues would need to be
overcome before any epo study could start. Worse still cyclists would need to
volunteer for a “ban” so it also need an end of career altruistic act.
If such a study were performed, my suspicion is that it would show that
epo microdosing is no more effective than a strong placebo. I suspect blood
transfusions or high dose epo would
outperform placebo, but I doubt those more severe studies could be done. Still
I don’t “know” these answers – as a scientist I just want the studies to be
done (ethics permitting) to find out!
