Lots of opinions on the subject of training!
I have a few thoughts that I'll add - would love to make comments on many of the posts so far but I waited too long and now there are too many! So I'll go general:
- Be careful when using the best athletes in the world when drawing conclusions about the effectiveness of training. Talent trumps training every time. The best in the world could do nothing but sit on their butts watching tv for training and would likely still be the best. If you want to see what training works, look at the people with incredible longevity at the top: they tend to be the ones who know how to train. I don't think you'll find many who don't do heavy lifting.
- It's important to remember that strength and size are not interchangeable. Heavy strength training will not build size for most people, but it will build strength. You build size through higher time under tension (TUT). Heavy lifting is typically done with too little TUT so does not build size. Size tends to only be an advantage in contact sports (hockey, football, basketball - yes basketball), but not typically in other sports.
- New skis mean we can go faster with less effort, but it also means we have to be stronger to be able to tolerate the higher forces. I look at what happened with the Canadian alpine team ahead of the last Olympics (we lost almost have the team to knee injuries) and I assume a team who has a training problem.
- For me, the biggest reason to train is injury risk reduction. This is true for all sports, including running. A good number of my clients are runners trying to return to their activity after injury. None of them did strength training prior to injury. All of them are convinced of the value now: allowing them to keep running with less risk of injury.
- For rec skiers, the value of training is both injury risk reduction and improved conditioning. The feedback I get from my clients, who are primarily recreational athletes, is that they ski/run/play ultimate/soccer/hockey/tennis now without back pain, they move on the court faster, and they don't get tired as quickly as they used to.
- Further to the point about rec skiers - most are people with desk jobs, which comes with poorly functioning glutes, and overly tight hip flexors. If you add a weak core to that, you have the perfect storm for low back pain. Smart training addressing strengthening and flexibility works wonders.