400m and the 43-second Barrier

The 100m has 10 seconds, the 200m has 20 seconds and the 400m has 44 seconds. Thus far only one athlete in history has managed to dip under all three of these magical sprint barriers: Wayde van Niekerk.

Last year I wrote a piece where I theorized about the possibility of a sub-19 seconds 200m run. And while I estimated that the current human limit is at 18.8 seconds, I did conclude that 19.00 (and lower) is decidedly beyond the reach of any professional athlete competing today (maybe there’s a special kid somewhere that we haven’t seen yet).

So forget about that for now and forget about the 2 hour marathon. The next big barrier in athletics is a 400m race run in under 43 seconds, and it might be just around the corner because Wayde van Niekerk has conclusively proved that it’s already possible without having to resort to theorizing about perfect splits!

All we need is some simple arithmetic based on what we already know about his world record of 43.03 seconds.

Firstly─and probably most importantly─his reaction time in Rio was 0.181 seconds, which is acceptable in terms of running the 400m, but it gives him some room for improvement as he effectively covered the distance in 42.85 seconds, which is surprisingly even faster than Michael Johnson’s flying relay split of 42.91* from 1993. For comparison, Johnson had a reaction time of 0.150 seconds when he ran the previous world record of 43.18 seconds in 1999 in Seville, which means that he covered the distance in 43.03; what a nice foreshadowing :).

*official IAAF sources range from 42.91 to 42.94. 

If Wayde van Niekerk managed to have a perfect start of 0.100 seconds, he would have run 42.95! But, more realistically, he could have run 42.99 if he would have matched Kirani James’ reaction of 0.134, which was the best reaction of all the Olympic finalists in Rio.

In short, van Niekerk’s potential in Rio was:

  • 42.85 – with starting blocks & without reaction time,
  • 42.95 – with a perfect reaction time of 0.100 s,
  • 42.99 – with a realistic reaction time of 0.134 s.

He really was and still is tantalizingly close to 42.XX.

However, is it possible that the 43.03 run was a once in a lifetime performance? Maybe, but I don’t think so, even though there is always a big possibility that the athlete has peaked when they’ve already run a world record.

What gives me a lot of hope is the fact that he’s still improving his top end speed and hopefully not at the expense of speed endurance. He has run a couple of races this year and so far he definitely seems to be on track to be in just as good a shape (if not better) as he was last year at the Olympics.

If he does indeed manage to come to London World Championships in form, then I think that there’s a definite possibility of him going under 43 seconds this year. That is if he peaks at the right time and runs his best race of the season on the biggest stage (like he already proved capable of doing in 2015 and 2016).

Van Niekerk standing proudly next to his World record of 43.03 seconds in the 400m. The race is on to become the first human in history to go under 43 seconds and reach immortality in the sport. Van Niekerk proved that it is possible by running 42.85 seconds if we subtract his reaction time of 0.181 seconds. But will he be the one to do it?

I’m confident that van Niekerk is the man to beat in the 400m, but the thing that has me slightly worried going into this season is – dare I say – his hubris in trying to also run the 100m & 200m. The latter two are actually his favourite events, but he moved up to the 400m a few years ago due to hamstring problems.

In a lot of ways he is like the male version of Allyson Felix. The depth and quality of their personal bests ranging from 100m to 400m is currently unmatched, but I hope that he doesn’t get overburdened by running all three of the sprint events this year. I know that Wayde is only doing the 100m as training for the time being, but he will still try to emulate the great Michael Johnson by going for the insanely difficult 200/400 double in London. The competition schedule has recently been changed to accommodate his wish, but it still means that round 1 of the 200m is gonna be held just two hours before the 400m final. He’ll want to conserve as much energy as possible, so it might work against him if he’s placed in a tough group where he’s gonna have to work harder than he’ll want to to get through.

In any case, doing the shorter sprints will definitely help with his speed, but the question of whether this will permit a faster 400m remains.

200m & 400m Correlation

A lot of interesting comments were posted to my analysis of van Niekerk’s record-breaking run, but the following one stuck in my mind ever since I first read it:

“Over twenty years ago I wrote an article about USA 400 meter runners. What the article simply stated is that any 400 meter runner who could run under 20 seconds in the open 200 meters is capable of running 43.0 or better if they are willing to get in the right condition.” – James Robertson

James Robertson

It’s definitely a plausible statement, if only slightly optimistic in a way where it proposes that a 20.0 s 200m athlete is capable of running the first half of the 400m in ~21.0 and the second half in ~22.0.

The quote also indirectly refers to the famous formula for predicting the 400m time, which is done by multiplying the 200m time by 2 and adding about 4 seconds for slowdown.

Formula 400m potential

We obviously want the slowdown to be as small as possible, but I just want to point out that it’s never gonna be less than 0s in the world of competitive sprinting, i.e., it’s impossible to run a truly fast 400m time by running any 200m split faster than your 200m personal best. This is in contrast with the 200m where your second (aka flying) 100m should always be faster than your regular 100m with blocks.

With that out of the way, let’s look at Johnson’s season best times in the 200/400 (with S for slowdown) and see if we can find anything useful.

Johnson times

(slowdown: S = t400m – 2 x t200m)

Keep in mind though that he might have been in better 200m shape when he ran his 400m season’s bests and vice-versa (he ran some SBs months apart for example).

Johnson’s slowdown when looking at his 200/400 PBs was 4.54 s. His best seasonal slowdown was 3.06 in 1998, arguably because of a rather weak 200m time, and his worst slowdown was 5.55 at the beginning of his career in 1988. His average slowdown of 4.28 over the span of his entire career is proof that our standard formula with a 4 second slowdown is a fairly good predictor of the 400m potential based on 200m.

Van Niekerk’s 200m SB in 2016 was 20.02, so his slowdown in the 400m was just 2.99 seconds (S = 43.03 – 2 x 20.02). This leads me to believe that he was either capable of more in the 200m or that his speed endurance was phenomenal. It’s likely a combination of both as he has already run 19.90 at the beginning of this season.

But speed always comes at the expense of endurance and the 400m is the definitive event for speed endurance. Outright speed or outright endurance won’t get you across the line in optimal manner, so a perfect combination of these two elements is key.

In any case, it’s obvious that a faster season’s best time in the 200m doesn’t directly translate to a faster 400m as well. Again, contrast this with the 100/200 combination where a faster 100m time will almost always translate to a faster 200m time.

So it seems to be the case that at some point having too much speed in the 200m becomes detrimental to your overall 400m speed endurance. Otherwise─based on our formula─you’d expect the likes of Usain Bolt (9.58/19.19 in the 100/200), Yohan Blake (9.69/19.26, but really 19.44), Tyson Gay (9.69/19.58) etc. to have much faster 400m times, but of the above-mentioned, only Gay managed to go under 45 seconds with 44.89 (he was the first athlete to go under 10/20/45 second barriers).

Usain Bolt in particular had the potential to be much faster in the 400m, but he never pursued it seriously because of (in his words) the grueling training demands of the longer sprint distance. If he did, his times in the short sprints would undoubtedly suffer.

Faster 100m almost linearly translates to a faster 200m time. Male athletes should be able to double their 200m time in relation to the 100m, but the 400m (as seen in the table above) is much harder to predict in this manner.

So if we plot the relationship between the 100m & 200m times, it would look something like this:


Meaning that the 200m time is usually double the 100m time (10.0 in the 100m should give you a ~20.0 in the 200m and so on).

And the plot for the relationship between the 200m & 400m is more like this:

ChartGo (2)

Meaning that there seems to be a sweet spot between speed & endurance that produces the fastest times in the 400m. For demonstration purposes I chose the sweet spot at 20.0 seconds because that’s the region where Johnson & van Niekerk had their SB times in the years when they broke the 400m world record.

This parabola can of course be moved to the left or right, depending on the data you use, so again, please keep in mind that this is just for demonstration purposes and isn’t supposed to be taken as seriously as the 100/200 graph.

Usain Bolt’s 19.19 for example doesn’t simply translate to 42.38 (based on our formula above), but closer to 46 s. His PB of 45.28 is from 2003 when his 200m PB was 20.13. Mind you, he was only 17 at the time, so we can sadly only speculate about what Bolt’s true potential was, but I’m confident that it was deep in the low 43s.


In conclusion, I will say that Wayde van Niekerk is at a unique moment in his career. He’s eagerly building upon the best two seasons of his career so far and the depth of quality sprinters in the 400m is better than ever.

I find a lot of parallels with Bolt’s record-breaking period of 2008 & 2009. Wayde is still on a realistic path of making progress and it truly is a mouthwatering prospect to imagine what he could run in the 400m if he manages to couple his amazing endurance with the newly developed speed.

I’d say that there’s a big chance of us seeing at least a sub 43.5 time this year and about a 30% chance of 42.9.

Žiga P. Škraba

6 thoughts on “400m and the 43-second Barrier

  1. Ernest G Hamilton 16 May 2021 — 02:57

    Van Niekerk only had two years where he was at the top of his “game”, so to speak. He has only run under 44 seconds two or three times and has run under 20 seconds maybe three times. Let’s wait to see if he can improve on that world record. He isn’t 30 years old so he’s got time. Some of Michael Johnson’s best times came when he was in his early 30’s. Everyone will know in a few weeks who will be the top 400 meter runner after the Olympics are over.

    Liked by 1 person

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