I'm not fast.* I've only podiumed once in an event worth mentioning - always the prizemaid, never the prized! - and my PBs, whilst being times I'm proud of on a personal level, are nothing to write home about. My running style which, taking a lead from kung fu, I have named "Badly Co-Ordinated Praying Mantis" does not lend itself to speed: flailing around in the hope that my limbs propel me in generally the right direction is not the epitome of good, efficient form. I'll be puffing around the track on a Tuesday night at a Harriers training session, eyeballs out, straining to hit low 70s for 400m, and some pesky kid will knock out a sub 60 as if they could do it all day. Some of them probably can, or at least for multiple reps.
Coming to the sport as an adult, something I remember from early 'beginner' training plans in the likes of Runner's World is the emphasis on building up distance. Speedwork of any kind was the Devil Incarnate until you started looking at occasionally 'intermediate' plans but, more often than not, 'advanced' plans. Speedwork carries a higher risk of acute injury, it's true, and that's particularly so for the older runner whose muscles and tendons maybe aren't as elastic and resilient as they once were. However, I'm not aware of any reason why that injury risk decreases with experience, other than perhaps that you get better at warming up and listening to your body.
Compare that with my understanding of youth training, and there's quite a contrast. Much more emphasis is put on speedwork, and the distances raced are shorter; the kids learn how to run fast before worrying about learning how to run long. So why do adult beginners get taught to do it the other way around?
I read something somewhere - probably the "World Famous Message Boards" on LetsRun.com, so a hefty pinch of salt may well be needed - that said that top end speed was genetically pre-determined, and the majority of the training a sprinter undertakes is about developing their technique to utilise that. Aerobic endurance, on the other hand, is seemingly limitless in terms of development potential. The general progression of distance runners, with a few exceptions, is to only move up in distance when they've maxed out their performance at the shorter distance. See: Kipchoge, Bekele, Gebrselassie, Rupp, Farah, Radcliffe, Flanagan, Goucher... The marathon is what distance runners retire from.
So, quick summary: kids develop their technique first to best utilise their genetically pre-determined speed, and then undertake the comparatively easier task of developing endurance later on. Adult beginners develop endurance and then rarely work on speed, and the majority almost certainly not with a coach to correct their technique.
Why, then, do we not have adult beginners doing speedwork? Perhaps, because most adult beginners are self-coached and therefore have no-one correcting their form, the risk of acute injury (which is actually pretty low when we're talking about threshold runs and longer intervals) is considered to outweigh the benefits; if all you want to do is complete rather than compete, does it matter how fast you do it? If doing a marathon once is a bucket list event, you're going to PB by default.
Those kids at the club running sub 60 400s - with a few notable exceptions - aren't going to be able to keep up over longer distances; I'd drop them within a few kms. When they mature and develop their endurance at speed, however, that will change completely; they'll be combining technique with aerobic endurance and that, dear reader, beats pure endurance any day of the week. They'll be fast in a way that I am not.
So is speed a case of nature or nurture? Clearly, from the above, I consider it both; adult beginners rarely benefit from the nurture, however, and so nature isn't tapped. I'm sure I'm not the only person to suggest this, but I wonder whether adult beginners should train more like kids, with the grounding in speed, not endurance; learn how to do it right before you try and do it for a long time. Of course, as I've said previously, the problem is that speedwork is harder and more unpleasant than endurance work, even if it pays dividends, and so the attractiveness of the long slow plod, perhaps with friends or in beautiful places, wins out over the lactic acid sufferfest round the track or on the deserted roads of an industrial estate. It's taken me a while to embrace the interval work and threshold runs, but the benefits are undeniable. Unfortunately, neuroplasticity diminishes with age - it literally becomes harder to teach an old dog new tricks - and so technique is a constant battle; the muscle memory just isn't there to keep good form at the end of a long race. Would it be, if I had trained as a kid, or even focused more on it in the early stages of my running career? Almost certainly.
A bit of a ramble, but that's what happens on a dreary Monday morning. Anyone with any kind of background in coaching or sports science who would like to tell me I'm talking nonsense, feel free!
*In an attempt to avoid being "that guy" who makes other people feel inadequate, let me be quite clear that I'm talking about my place relative to people who might reasonably be considered my peers, in dedication to the sport if not actual performance. The serious club runners who are hitting upwards of 100km and who knock out the holy trinity of intervals/threshold/long slow run every week. I wouldn't ever want to put someone else down, even unintentionally; everything is relative and what's slow for me might be a lifetime best for someone else, in which case have a hearty "chapeau!" (the same works the other way, of course... Kipchoge and Bekele run their recoveries at my PB pace!). A very hamfisted and probably patronising attempt at a disclaimer, but hopefully the intention is clear.