I remember reading similar discussions on the 800m on the 'Science of Sport' website some time ago.
The whole article can be accessed here.
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Below is the extract relating to split times. This was written in September 2007 - before Rudisha emerged to break the world record. Wilson Kipketer held the WR (1-41.11 in Cologne, Germany on 24/8/07) at the time this article was written. 800m – it’s not possible to run optimal times with a faster second lap
The 800m distance is a fascinating one, and well worth discussing further, because it straddles the divide between what people usually refer to as “sprinting” and “middle distance” running. To some, it is the first of the middle distance events, whereas to others, it’s the last of the sprints. Of course, using such jargon can pose challenges, but generally, when people refer to a sprint, they refer to an event where the athlete goes ‘flat out’. This is of course never true, because even in a 200m race, there is some pacing, as evidenced by people who go out a little too fast and end up faltering in the final 40 to 50m!
However, the fact remains that the 800m is a unique distance, requiring a combination of sprint ability and endurance ability. Coaches (and physiologists) have often spoken of an aerobic-anaerobic divide for different events, and they often refer to the 800m distance as being a 50% split for each. That is, they say that approximately 50% of the energy comes from aerobic sources, 50% from anaerobic. This is a contentious issue in itself, one that I would argue with, as recent evidence suggests there is no black and white split between the energy sources, as is often put. But anyway, that’s another story altogether, back to the 800m event.
In the 800m event, 26 world records have been set. The top graph below shows the average lap times in these 26 races. It’s immediately clear that the second half is quite a lot slower than the first. Some of you may be thinking, hang on a moment, what about the 200m splits? Unfortunately, they are not available for the 26 world records, but in the ones they are available, they follow the same pattern – the first 200m is fastest, followed by the second, and the pace gets slower and slower.
So this is a departure from what we’ve seen before – suddenly, speeding up at the end doesn’t happen. In fact, in the 26 world records, the second lap has only been faster than the first on two occasions. Therefore, a world record seems to require that you run a fast first lap, and then hang on in the second, but speeding up does not appear to be an option.
Some of you may now be questioning this statement. Among the biggest challenges would be the assumption that you’re seeing ‘optimal performances’. And of course, this is true. If a guy goes out and run 1:46, who is to say that is not optimal? Perhaps it is. However, I still maintain that with this pacing strategy observed in 24 out of 26 world records, the best way to run the race is to run the first lap faster than the second. On average, the difference is 2 seconds. This means a first lap of 50 seconds would be followed by a second lap of 52 seconds.
What is even more interesting is that the two fastest second lap times ever achieved in 800m world record performances were run in 1972 and 1966 respectively.
The graph below shows the lap times from all the world records, and if you look at the panel on the right, you will see that the second lap time of a world record performance has not improved in 35 years, since Dave Wottle broke the world record with a time of 1:44.3 (min:s) and a second lap of 51.40 seconds in 1972. The current world record holder, Wilson Kipketer, has broken the world record on three occasions, with second lap times of 52.12, 52.90 and 51.80 seconds. Therefore, a 3.2 second reduction in the world record in the 800 m event between 1966 and 1997, from 1:44.3 to 1:41.11, has been achieved by running the first lap significantly faster, rather than an improved ability to increase running speed on the second lap.
The Figure below shows the lap times for the 26 world records in the 800m event. The left panel is the first lap, the right panel is the second lap[You must be registered and logged in to see this image.]
Another interesting fact is that even in the Olympic Games, where the first lap is often tactical and slow, is the second lap slower. The average first lap in the Olympic Games finals is 52.8 seconds and the second lap is 53.4 seconds. They slow down, even with a faster first lap! In otherwords, even if the athlete slows down and runs the first lap quite slowly, the second lap is still slower.
What this suggests is that the ability to run faster during the second lap of an 800m is limited, and so the optimal pacing strategy may consist of a faster start followed by a relatively slower second lap.
I’m going to go out on a limb here and say that if you are an 800m athlete, or you are coaching an 800m athlete, if you want that athlete to run their best, you have to plan for a second lap that is about 2 to 3 seconds slower than the first. So, if the goal is 2 minutes, it’s not good enough to aim for a first lap of 60 seconds. It has to be 58-something, because if your athlete is going maximally, then he should slow down to a 61 on the second lap, giving him a final time of 2 minutes.
Similarly, if you want to break the world record, forget about running the second lap in 51 seconds. It’s not going to happen. Therefore, you must plan for a second lap of 52 seconds, which means the first lap must be 49 seconds. This is also an indication of the sort of speed needed to challenge Kipketer’s world record – you have to be able to run a 400m in 48.5 seconds as part of an 800m race. Your basic 400m speed therefore needs to be down in the 45’s, maybe 46 seconds (but that starts cutting it fine).