I totally agree with Intheclouds - functional training is the way to go. But that doesn't typically mean standing on bosu balls. (Not saying don't do that - just that it's one of many tools and not necessarily a good first step). And yes, I am a professional trainer - at a sports therapy clinic, so I spend my days assessing people's movement abilities and limitations and creating custom training programs for them.
I just got out of an intensive two day golf fitness seminar, and if you're looking for balance, I'd suggest you check out the mytpi.com website. the TPI (Teitlist Performance Institute) has put together a complete movement screen for rotational athletes (skiers are rotational athletes although slightly differently so than golfers/tennis players/baseball players), as well as a full set of corrective exercises. You can access the exercise descriptions and videos on their website for free. Go to the exercise library and check out the corrective exercises for the single leg balance test.
The great thing about the TPI stuff is that it was created by a great team, including top chiropractors, physical therapists, and strength coaches.
Also - look at their stuff for training juniors. Their juniors training program is based on the Canadian Long Term Athletic Development model, which is a model that many countries are now following. I've found that with the teenagers I used to coach, many of them lacked some fundamental movement abilities (think skipping, jumping, kicking, throwing, rolling, climbing, shuffling) and so I started including them in our practices. There's a trend in the fitness industry to go back to some of these basics as part of our programming because fundamental movement is required for more advanced movement to be successful.
Good luck!
Elsbeth
