Why the running track is exactly 400 meters long

HostIt seems like every high school or local park has that same big oval loop for running. We all kind of just know that if you go around it four times, you have run about a mile, but the math is a little off because the track is actually 400 meters. How did we land on that one specific number instead of something like a nice, round 500?

GuestIt's a bit of a messy story that comes down to a fight between two ways of measuring the world. For a long time, especially in the US and the UK, people ran in yards. A mile is 1,760 yards. If you want a nice shape that fits inside a field, a quarter of a mile is the perfect size. That's 440 yards. So, for a huge chunk of history, tracks weren't 400 meters at all. They were 440 yards.

HostSo everyone was just fine with the 440 yard loop, and then someone decided to make it slightly shorter just to make the math harder for everyone else?

GuestWell, it was the rest of the world that pushed for it. Most countries use meters, and they wanted a number that felt clean in their system. 400 meters is about 437 yards. It's so close to the old 440 yard track that you could almost use the same dirt. But for a long time, it was a total headache. You would've runners from England training on yard tracks and runners from France training on meter tracks. When they met up for a big race, the lines on the ground literally didn't match up.

HostThat sounds like a mess for the people timing the races. Did they just have to move the finish line every time they changed countries?

GuestBasically, yes. It stayed that way until the late 1970s. The big turning point was the 1976 Olympic Games. That was the first time they really set the rule in stone that 400 meters was the only way to go. If you wanted to host a world class race, you had to build your track to that exact size. It forced everyone to pick a side, and the metric system won out. Now, even in the US, almost every new track you see is the 400 meter version.

HostOkay, so we have the length settled. But why that specific shape? If we just need 400 meters, why not a big circle or a giant square? Why do they all look like a flattened pill?

GuestThe shape is actually very clever because it has to serve two different masters. You have the long distance runners who need to go around and around, but you also have the sprinters who run the 100 meter dash. Sprinters hate curves. When you run at full speed, turning your body actually slows you down and puts a lot of stress on your knees and ankles. To make the sprinters happy, you need a long, straight flat stretch of ground. So, the track is built with two long straight sides and two curves. Each of those four parts is roughly 100 meters long. That lets the sprinters have their straight line, and the distance runners get their loop.

HostBut that seems unfair for the people in the outer lanes. If I'm running in the lane furthest from the grass, I'm running a much wider curve than the person on the inside.

GuestYou're totally right. If you both started at the same line and ran to the same finish, the person on the outside would run a lot further. In fact, if you go from the very inside lane to the very outside lane on a standard track, the distance changes by about 7 meters every single lap. That's why you see the runners lined up in that staggered way at the start of a race. The person on the outside starts way ahead of the person on the inside so that by the time they finish the loop, they have both covered exactly 400 meters.

HostIt still feels like a lot of work just to keep a loop at that specific length. Is there something about the human body that makes 400 meters a better test than, say, 300 or 600?

GuestThere actually is. Coaches often call the 400 meter dash the longest sprint. It's a very brutal distance. Most people can run at their absolute top speed for maybe 30 to 35 seconds before their muscles start to fill up with waste and their brain tells them to stop. A world class runner can finish 400 meters in about 43 or 44 seconds. That means for the last 10 seconds of the race, they're basically running on empty. Their body is screaming at them to quit. If the track were much longer, it wouldn't be a sprint anymore. It would be a game of pacing and breathing. At 400 meters, it's a test of who can hold onto a total explosion of speed the longest.

HostSo it's less about the math and more about finding the limit of how long a person can move at full tilt.

GuestExactly. It's the sweet spot where the physics of the ground, the math of the mile, and the limits of our muscles all meet. We have built our stadiums around this one specific limit of what a human being can do.

HostThe 400 meter loop stays the same because it's the exact point where a human sprint starts to fall apart.

GuestThe red dirt loop is a clever trick to squeeze a mile into a space that fits in our neighborhoods.