Changes

If we go from standing to running at race pace (or faster), our oxygen delivery will lag behind our oxygen consumption as our heart rate [[Heart Rate]] gradually increases, causing an oxygen debt (see image below). This oxygen debt causes us to be too anaerobic for the race. So even if we go out at race pace, without sufficient [[Warmup]] this may still be 'too fast'.

Going out too fast is caused partly by the excitement of the race. This excitement releases a surge of adrenaline, which changes our perception of effort and time. I've seen my heart rate [[Heart Rate]] while standing at the start line reach well over 100 BPM, a sign of the adrenaline that has been released. A good [[Practical Tapering|taper]] will cause us to feel far stronger at the start of the race than we do in training, compounding the effects of the adrenaline. Another factor behind going out too fast is the optical illusion of having runners around you. On most training runs we have nobody blocking our vision, so we see our forward motion represented by the ground and scenery appearing to move towards us. These visual clues are an important part of our sense of pace. At the start of most races, all we can see is other runners, with little of the ground or scenery visible. Because most of the runners will be moving a similar speed, they will appear stationary, and a key visual clue to our pace is lost. If the other runners are actually going faster, then the illusion becomes more intense on we can get a sense of moving backwards even though we are running faster than we should.