Some studies suggest the "aerobic energy system contribution" in the 400 is surprisingly high, e.g. this one says 43% in highly trained people (PR 45.7-49.5 seconds):
i'm so serious when i say this what is up with this influx of idiots during trial and olympic season
Sprinters don't run all 3 events because rounds at national and international championships conflict with each other. Simple as that. Can't do a round of the 400 and then come back to run the 100 final 30 minutes later. Looking at the schedule for USAs and the Olympics could have told you everything you need to know.
A guy won the 100/200/400 at our state meet a few years ago in like 10.5, 20.9, and 46.3, and ran all of them in the span of like just over an hour. If some noname high school kid can do that, you're telling me pros can't? Come on man
Anyone can run them, but if the intent is to win, then that won't happen. In all of global championships since they have been in existence, only 3 athletes have ever successfully won the 200/400 double. Imagine adding another event to that mix.
Once again, the training for the 100M is remarkably different from the requirements of the 400M. The aerobic requirements is also vastly different for the 100M than it is for the 400M.
Genetics determine which events are run by a particular athlete. A 100/200 guy is not going to be as competitive at 400, a 400/800 runner not at 1500m, an 800/15000m at 5000m and 15/5 at 10000m.
So many on LR believe anyone can move up out of their range and be just as good.