I think the 3:57 miler would feel more discomfort, but not by much. I can't speak for running but I know that they test lactate levels in swimming, and I believe the highest level tested was 22 millimoles, which was Matt Biondi, who just happened to hold about 5 American records at the time. But it wasn't like he was 22 and everybody else in the world is 10. So my opinion is that the world-class guy is hurting just a little bit more.
If you ever read interviews with El G or Lagat or others like them, they will say things like "I tied up the last 40 meters." Yeah, who doesn't? But I think what they are saying that they tied up beyond what most of us are even able to get to.
If a world class marathoner has a superior aerobic system than us mortals, wouldn't it make sense that a world class middle distance runner would have a superior anaerobic system than the rest of us? In other words, that they would be able to create more lactate?
Again, I don't think it is a huge difference. If you put a muscle fiber in a solution that is below a certain pH, it WILL NOT contract, no matter what electrical charge you run through it. So you can only override the lactate level with superior desire/pain tolerance up to a point. After that, you can be sending all of the nerve impulses that you want to the muscles and they are not physiologically capable of contracting.
Sean Nunn