Strength Training for Runners

The body is a chain of muscles,bones, tendons, ligaments and fascia. Like a chain, if there is a weak link, it will affect the whole thing. The entire organism is the sum of its parts.

That much is fairly obvious, but I need to start at the beginning.

Running as a muscular action tends to use a fair amount of these muscles and tendons to create and harness the power that propels you forward. (Hopefully at a decent velocity) its not just your leg muscles, or just the rebound in you calf muscles and achilles tendon. The whole thing works as one. 

Running is an interesting action, but is a little to complex to go into biomechanically here. Suffice to say that it is a series of one legged jumps, landing on one leg.

If I asked you to stand on one leg and balance, could you?
How about 20 calf raises on one leg?
Or 20 hops in one place?
Or a hop up to a platform?

You might think that you'd be getting tired by now, but think about how many single leg hops and jumps you do in a kilometre. Multiply that by the length of the race. Then think about the rough terrain you're going over.

If you get tired, or find it hard to stand on one leg, or do hops or whatever, yet you manage to run decent distances, how much easier would it be, how much faster could you be if you were competent at a few basic human movements?

We don't train for when it's easy.
We train for when it gets hard. 

As an example. Glutes. The ones that make up your bum. Huge muscles that control hip movement, explosive power and also knee stability. Is your knee stable as you run uphill? How about down? That's when the maximum force is applied through the joint. If your glutes aren't working right, or lack the strength you need to get down that hill easily the joints will start taking the strain, and pretty soon you'll have knackered knees.

The answer? Controversial, I know, but resistance training. Using a controlled environment to learn to engage muscles in certain movements, to work out which muscles are working sub optimally, and subsequently reeducate them to work in a sequence that enables you to run with more efficiency.

Yes, I know the argument about not wanting that bulk up, but that is null and void.
Also there is the dislike of weight training environments. No I can't change your attitude there either.
What I can do is tell you the benefits of weight training for running, and if you want to run faster, perhaps be less prone to injury, maybe you'll take note. Maybe you'll tread the path that most successful runners take.
No, its not a magic bullet, but as part of a varied programme of running, speed and hillwork, it can be that link which gives you that little bit extra.