Fartlek

Fartlek, (Swedish: “Speed Play”), approach to distance-running training involving variations of pace from walking to sprinting aimed at eliminating boredom and enhancing the psychological aspects of conditioning.
In simple terms, starting as a jog , slowly increasing your speed and ending it as speed run.

An activity runners do when they change between sprinting and jogging

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.

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.

A form of cross-country training originally from Sweden, but adapted to a city environment. Like traditional backcountry fartlek, stoplight fartlek involves changing the tempo of the run, except instead of instinctually changing pace, the speed is governed by traffic and lights.