Ok, many of you have heard the story by now, train/practice for 10,000 hours and you will be the best in the world, a champion, an outlier etc.  It's the stuff of dreams, you can be the best if you just work hard enough.  That's an idea that sells a lot of books.

Unfortunately, it's wrong. Or to be generous, it's incomplete.

I first read about this 10,000 hour thing in Dan Coyle's "The Talent Code".  A good book, with lots of things to learn from from a coaching perspective.  I've adopted a lot of what Coyle wrote about in my coaching practice, it's good stuff, but it's missing something fundamental.  It's also the fundamental argument made by Mathew Syed in "Bounce".  Notably, Syed is a table tennis player, perhaps not the most physical of sports.  In the recently published "The Secret Olympian" (anon, but it's a British rower, a bit of googling will tell you who wrote it), "anon" writes :

Syed's argument in Bounce - train enough and you'll be excellent at whatever you choose - is seductive.  It's probably true for table tennis.  But in general, it's wrong.  As Bas van de Goor neatly states, 'You can learn to play volleyball; you can't learn to be tall.  Genetics count'.

These guys are not going to be successful volleyballers, not if they spend 20,000 hours of practice in the best hotbed in the world.  Genetics matter.  You can't be an elite athlete in most sports without winning the genetic lottery at birth.  Sure, if you train you will improve, but how good can you get?  Can you be the best at the world at whatever you choose to?  Only if you've got the right genes.  If you want to sprint, and you don't have working ACTN3, forget being elite.  It just won't happen.

A good article on some of the basic genetics behind sprint performance states :

ACTN3 is just one of many factors influencing athletic performance
At the highest levels of performance ACTN3 genotype certainly make a big difference: among Olympic-level sprinters the frequency of individuals carrying two disrupted ACTN3 copies is vanishingly low (less than 3%, compared to ~18% in the general population). However, this large effect is due to the exceptionally strong selection that occurs during the slow climb to the Olympic level. The vast majority of athletes who start that climb will never make it to the top; those who do will be the tiny minority who have nearly everything in their favour, including the right genes.

So super-elite athletes need to have the right ACTN3 combination, but they also have to have a whole host of other factors working in their favour – this one gene is just a minor ingredient in a large and complex recipe. In fact, most studies performed so far suggest that ACTN3 explains just 2-3% of the variation in muscle function in the general population. The rest of the variation is determined by a wide range of genetic and environmental factors, most of which (particularly the genetic factors) are very poorly understood.

 So what does that mean?

You can train your backside off, but unless you're gifted with the right genes, you're not going to be an Olympian.  You will improve, but your upper limits are genetic.  Having the right genes is not enough, not by a long shot, the world is littered with people with the genes to be superb who for whatever reason ended up couch potatoes, but it is a very important part of mix if you want to be an elite athlete.