“…Oxygen saturation, glycogen levels [7] and metabolic fuel reserves, for example, act not just as metabolic by-products, but as internal signallers [1] . On the other hand, environmental conditions such as gradient, terrain, weather, oxygen content of inspired air, knowledge of the event (for example distance or duration] [8] , previous experience [9,10] and competition [11,12] all equate to external cues [13][14][15] .…”