As I tell our campers, if you want to become a better runner, you need to do one thing-run.
Around the running, though, you need to build a calendar of training with the question in mind, "What is the purpose of each workout and each training block?"
One thing I think a lot of young runners ignore is strength training. A lot of the excuses I hear are, "I don't want to bulk up!" or "I don't have time for an hour each day in the weight room!"
One, runners are Ectomorphs, which means they literally cannot bulk up unless they were to stop running altogether and start eating thousands of additional calories each day.
Two, with running as the primary focus, young runners don't need an hour each day in the weight room. But 30 minutes, three days a week will improve performance. Make sure your weight training days correspond with your hard running days. Make your hard days hard, your easy days easy.
What does strength training do for runners? I believe it makes them more injury proof and more dynamic.
The question a lot of folks ask when developing young runners is, "What makes them faster?"
There are a host of answers, but I think one of the key ones is, "Uninterrupted training."
The stronger a runner is physically, the more punishment they can handle and the less injury they will face. Strength training not only develops stronger muscles, it develops stronger connective tissue and more bone density (critical for younger female runners).
Where to start? Put a plan together for workouts that last 20-30 minutes, 3 times a week. Identify your weak spots. Most runners fight a weak posterior chain (think hamstrings and back, both lower and upper). For introductory lifts, think basic. Hamstring curls, leg extensions, bench press and back rows. Shoot for a weight on each that enables you to lift 6-8 reps per set. You are looking to build strength. Resist the urge to do sets of 12-16 reps. There is no purpose for that kind of lifting. Body builders do those types of sets because hypertrophy leads to bigger muscle gains. It sounds counterintuitive, but it's not.
As you progress, start thinking about adding some lifts to the ones above. Think squats and deadlifts, maybe even some One Armed Snatches. Allow for gradual adaptation (i.e., don't lift too much too soon and get injured) and always focus on technique. Better to lift lighter with good technique to begin with than too heavy with bad technique. The latter will inevitably lead to injury.
Can strength training make you faster? Yes. I believe Olympic style lifts and plyometrics can make you a faster runner. Combine these elements with hill bounding and some Repetition work, and you will be amazed at your new speed.
So if you're not in the weight room three times a week, carve out some time over this winter, put together a common sense plan (some starting ideas are here) and get started!