Interesting leading article in the British Medical Journal. A large Scandanavian study has confirmed that warm up exercises before pivot sports (includes rugby) significantly reduce knee and ankle injuries in youth sport.

Moderate injuries were reduced by more than 50% and severe injuries (eg cruciate ligament tear) by significantly more.
The study also suggests that intervention programmes with training that encourages balance and positional awareness especially of the knee and ankle produce long lasting benefit and are best instituted very early ie less than age 12.

The original paper recruited handball players and is available on there are some pictures and specific exercisies.It is really the principles that are important rather than a specific series of exercises.

There are a number of reasons why early intervention makes a difference (many of you know how boring I am when I get on this subject). This study is important because it confirms that how you train very young kids not only affects their performance but also significantly reduces their risk of serious sports injury when they are much older.

I think the key coaching message is that relatively simple principles can be adopted into sport specific and age specific drills/games. That is really the long term goal, rather than spending 15 minutes of every session doing the same specific repetitive warm up exercises the kids would be training/playing (warming up)without even realizing that one of the specific goals of the session is to improve their balance and positional awareness in the same way that you may set a specific goal to improve their penalty taking or tackling.