This statement is deliberately full of multiple meanings, which is why it sounds a little odd. The writer has stretched the meanings a little.
'Pretreatment' and 'Condition' are alluding to beauty or hair treatments. Conditioning is a process that you do to hair after you have shampooed it.
But these words can also be interpreted literally. Here 'condition', as Marty said, means 'prepare yourself', or 'get ready', and 'pretreatment' suggests preparations that you could make for yourself before something. Top runners 'condition' themselves prior to a particularly demanding race or event.
You haven't given us the text that relates to what that 'something' is, but we can guess that it is some task or event that needs confidence.