I used to run middle distance in high school track and won several races in the 400m or 800m events. At the collegiate and professional levels, there is a lot

I used to run middle distance in high school track and won several races in the 400m or 800m events. At the collegiate and professional levels, there is a lot of specialization from what I know, but at the lower levels there are a lot of people who run both the 400m and 800m and even the 1600m or mile. I did. Runners who race in both the 400m and 800m are quite rare at the higher levels but not unheard of. The last time somebody won both the 400m and 800m at the Olympics was in 1976 [1]. I agree that a runner's physique plays a big role here, especially in regards to their mixture of muscle fiber types. At higher levels, I think it is easier to train a 200m runner's endurance than to train an 800m runner's speed. The 400m is a sprint and if you do not have a good enough top speed, you will not win. Your question about intermediate distances is interesting. I have run 500m races (on indoor tracks) in the past and I rarely saw sprinters attempt the distance. I saw plenty of 200m sprinters run the 400m from time to time, but the 500m was just too much. This is likely because it really is just too long to sprint the entire time. Your anaerobic energy will be nearly depleted by the 400m mark, yet you still have to go 100 extra meters! Pacing, endurance, and strategy become important here, and most sprinters are not trained in these areas as much, but 800m runners are, since the race is one of the most strategy-intensive races in the sport, with the positive split strategy (running the first half faster than the second half) being what tends to get world records. That said, I think that with the right training, 400m and 800m runners could be competitive with each other at the 500m, and maybe the 600m, but I think the 500m is more likely to be the competitive distance here. [1] https://en.wikipedia.org/wiki/Alberto_Juantorena https://en.wikipedia.org/wiki/Alberto_Juantorena