Core importance?

You're a teenager. What more important is your are cultivating a relationship with Jesus.

I've always disliked core work and never noticed a difference when I was doing/not doing it. The most "running specific" core exercise you can do is practice running with good form, so I just do that 9 times out of 10.

This post right here? Probably bad advice.

You need a strong core to run fast. That you dislike doing it will never change that.

Reality is you need to do both (Practice running with good form), and also do your core work.

Anyway, back to OP. Listen to your coach and do your core work, whatever your team teaches you to do. You have an opportunity now to get ahead of it (and your competitors) because you're young.

2x/a day every day sounds like a lot. I'd focus more on form and doing the exercises properly. 20 mins a day completely focused and with good form 4x a week, which tires you out, beats the hell out of sloppy 2x/a day. If I were you, I'd go to your coach/assistant coach and set up a good core routine 3-4x a week and just start nailing that.

One more thing. Try not to focus or obsess on it to much. You said you've "boiled it down to a weak core" and while that might be right, keep in mind you can't do much to change your running form in real time. Don't try and brace your core too much while running or take your focus off the actual running part - those cues could hurt you. Running should ideally come effortlessly. The idea of strength training + core is that the strength gained carries over to your running, but that is a gradual process, and it's done naturally when your body realizes it has more strength in those areas - Your form should autocorrect itself over time if you have a true core weakness, but that could take 6-12 months. 2x core a day won't speed that process up - there are NO shortcuts.

https://www.cpdo.net/Lederman_The_myth_of_core_stability.pdf

Good overall conditioning is great for the 800. Especially for holding it all together in that last 150

Core strengthening is like glute activation, a whole bunch of baloney. Most people talking about it can’t even precisely identify what exactly the “core” comprises and where the strength deficits lie.

The advantage of a strong core is basic engineering. Your legs and arms can be as strong as The Rock's, but if they are tied to a flimsy base you are limited- at least in efficiency. The question to me is who gets the most out of core work? I think no doubt its the person with weak core. Not necessarily the person with a good core trying to get better. Watch pros run in person if you can, it's a revelation. These guys have no wasted energy. I do think that their core efficiency is 99% genetic, but maybe we can improve our own.

Now, to me core in not just sit ups. And where core work vs hip/pelvis work rank I don't know. But weak hips, flexors, extensors abductors adductors is going to make every step result in energy leakage. Its all about energy leakage (and ball bearings)

Nick has a few videos on this.

Yeah I think you're right. Core work may not be necessary for everyone, some may already have it without any extra work, but if you're deficient in your core, you're opening yourself up to a whole range of possible injuries.

You won't notice any difference from lack of core work for some time. Then when you do, it will take a fiendishly long time to build your core strength back up. Usually you notice when you get a hip, hamstring, or gluteal injury. Just do 15 mins 3-6 times a week. Better than missing 3 months of running in 2 years.

I think it's probably worth thinking about core in the broader context of strength and maintenance. Doing a bunch of situps isn't going to make you like a supreme runner, but doing workouts like planks, side planks, etc. in addition to workouts that help your stabilizer muscles in your ankles lunges, calf raises, squats, etc. Additionally, plyometric drills and mobility drills help as well.

These things aren't necessarily important on their own, but are quite helpful in reducing injuries.

As someone who had an issue that caused my glute medius and lower core to stop activating, you have no idea what you're talking about.

Core strength (and glute strength) is important for hip stability. If you're weak, other muscles try to pick up the slack and end up overused and injured. So you can end up with random hip adjacent injuries that make the root cause very difficult to track down.

As someone who wrote what they wrote, I have some idea of what I talked about, so you are wrong and a useless jerk while at that.

just run baby

Muscle being weak is not the same thing as muscle "not activating". If your lower core wasn't activating you wouldn't be able to take a single step.

Some people are vociferously against doing anything other than running. I assume cos they cant be bothered or dont enjoy the other stuff and just justify it by saying its unnecessary.

Overloading and specificity are opposite ends of the training spectrum. Running gives you loads of specific work but you will miss the overload training.