Going out too fast
Starting a race at too fast a pace is a remarkably common problem. We'll look at the causes, the consequences, and some solutions for this particular problem.
1 The causes
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 while standing at the start line reach well over 100 BPM, a sign of the adrenaline that has been released. A good 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.
2 The consequences
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 gradually increases, causing an oxygen debt (see image below). This oxygen debt can be disruptive to our aerobic systems and impair performance. This disruption comes last for protracted time and impact on race as long as a marathon.
For marathon races, where Glycogen reserves are critical to performance, going out too fast will burn a disproportionate amount of Glycogen. This is because Glycogen usage varies nonlinearly with pace. So if you run a mile at 7:45 and a second mile at 8:15, you will use more Glycogen than running two miles at 8:00 pace.
3 The solutions
There are two parts to solving the problem of going out too fast. The first, obviously enough, is to go out at the right pace. This is a tricky thing to achieve, because our sense of pace is disrupted by the adrenaline, taper, and the optical illusion of other runners. GPS devices are generally of little help, as they do not provide an accurate reading of the current pace. Setting a GPS watch to display average or lap average pace can help but it is quite a crude metric. Likewise, mile split times are too infrequent to really help. The best option is a sports watch that uses a foot pod to indicate current pace; see Best Running Watch for more details. Using a marathon pace group can work very well if the pacer is good, but sadly it is not uncommon for the pacer to go out too fast. The second part of the solution is to ensure a good Warmup. The correct Warmup strategy will depend on the length of the race, as a 5K is very different from the marathon. See Warmup for more details.
