pro runners dramatically crashing to the floor after finishing races

Maybe they just want to lie on the ground? Maybe some muscle is tight that they want to rest/stretch? Maybe they are just excited/disappointed in their race? It could be a lot of reasons outside of the two you listed, and it’s probably different for each runner and even each race.

I’m not a pro but I crashed at the end of a race once. It wasn’t for either of your reasons. It was because I wasn’t lifting my feet and my spike caught the track and I tripped. Falling on a rubberized track is not fun. I had like 6 bloody scrapes.

for example, watch the olympics and at the end of a 400m or 800m, half the field will lie on the ground for a good 60 seconds after they cross the line. typically knees up, hands stretched above head or to the side, like they are making snow angels. they sort of crumple to the floor like they have suddenly lost all control of their limbs. I am not olympic or professional standard, but I feel I give it my all in many of my races, and never have I felt the need to lie horizontal. occasionally I will bend over and put my hands on my knees for 10 seconds to catch my breath, so I get the need to recover in the immediate aftermath. it just seems a little too melodramatic. and they obviously know the cameras are there 🤷‍♂️

There's a physiological explanation that is particularly applicable to the 400 and 800. Those runners probably have higher fast twitch muscle distribution and much higher anaerobic capacities than you. Some of that's genetic, and some of that is in response to training. It means that they can finish their races in much more oxygen debt than you can. Notice that the 5,000 meter runners never fall over and hardly seem winded? It's because they are so aerobically efficient (and they have lower anaerobic capacities) that they aren't as deep in oxygen debt at the end of their races. It has been observed that some of the very best runners in the world actually have lactate thresholds that are close to 5k pace, which defies patterns observed in pretty much all other athletes. People on Letsrun usually comment on the phenomenon of the not-winded pro runner more than they comment on runners falling down.

There's also a psychological explanation. However much you think you care about your races, and however much you think you try, it's highly unlikely that you care as much as they do. You're not competing in front of millions. You haven't devoted your life to this. When your world is focused on a few seconds, months in the future, there's a sense of release to having them behind you.

Also, how do you know that you "give it your all" in many of your races?

Oh my!

I was going to mention the anaerobic thing but my knowledge isnt great on it. Maybe somebody can help me understand. Their muscles are using glycogen not oxygen right? But they are still breathing and inhaling oxygen, so how does that work, why are they in an oxygen debt?

And i figure i am giving it my all because at the end of a 5k my heartrate is 196. I know the 220 minus age thing isnt 100% accurate but that would put my max at 187. I must be there or there abouts in terms of maximum intensity.

They’ve conditioned themselves (through training, and also somewhat due to their genetics) to be able to run in a high state of oxygen debt.

Think of it this way - they can run a race above their “oxygen threshold” well the same way that elites can run 5-10k above their lactic threshold.

Depends on the event. When i raced 1500m i never felt the need to crash after my race, i was spent but its not lie down worthy.

However, now that i am 10 pounds heavier and race in the 400, i get a huge urge to lay down, but i try to refuse and walk slowly until i catch my breath.

"oxygen threshold" ???

Exactly

Its when you keep running despite not having enough oxygen.

Its called oxygen debt, i never heard of oxygen threshold tho.

Are you talking about decathletes after finishing the 1500m after 10 events in two days, doing mostly sprint and power events?

yes those guys also. sprawled across the track like they have been gunned down.

What catches my attention is the exact opposite - when all the runners are prone, post-race, except for one, invariably the winner in these instances, walking around smiling, shaking hands, barely breathless.

Drama - the look at me generation

Funny you don’t really ever see the winner falling to the ground, but the others look at me I gave everything I had can’t even stand up and I really tried.