From the German translation 'Speed Play', fartlek is a training exercise used by distance runners to increase their anaroebic capacity. This increases racing performance greatly by allowing muscles to better cope with the lack of oxygen associated with high-intensity activities. The process involves speeding up to race pace for several minutes, then jogging for several minutes, repeating until workout is over.
Uli did 2 hours of fartleks yesterday to get ready for the Seattle Marathon, he's insane!
Forced usage of alternating speeds and positions due to movements of ecstacy in cunnilingus, making it difficult to achieve maximum clitoral stimulation. In extreme cases, can result in having to start again, causing irritation to both sexes.
"She started moving her hips up, so I had to fartlek her. She hit me as she was 'so close', bringing shame upon my family name."