The latter sentence is actually true. It is a well known fact. That is why long distance runners make sure never to practice sprinting and sprinters as well as athletes that have to run short distances only (such as American football players) never run long distances during practice.
Anyways sorry for going off on an OT tangent. The internet must be rotting my brain.
Some runners do that. Others do not. My cousin is a D1 cc runner. He runs a lot of sprints in his training (mostly 400, 800m), but his shortest race distance is 10k. He is doing a marathon soon and an ironman is in the works.
Good football players often go jogging or do other continuous, light cardio for longer periods in general training.
It is sorta like how to be a good reader you need to be able to read/comprehend novels and academic articles -- imho.
Then I picked a bad analogy. It was already bad: reading is not a sport. The idea here: if you spend your time on the internet reading short-form, you'll become practically incapable of dealing with long-form prose. To which I say: bullshit, concocted to sell books.
Anyways sorry for going off on an OT tangent. The internet must be rotting my brain.