People often ask me at what age should a child specialise in a sport and I tell them no earlier than 12.
For every Tiger Woods or Dimitri Bilozerchev who is a child prodigy and comes along and dominates a sport, there are millions of children washed up on the sidelines with injuries or burn out.
The best movement program a child can do is one that covers all the bases.

One that teaches them great strength in relation to their body weight, body awareness, spatial awareness, safe landing technique, rotation, hand-eye and foot co-ordination, balance, flexibility and an ability to perform complex tasks that cross your center line.
If you’re lucky, you can get all this from the one program but in most cases this will ONLY be achieve by doing multiple sports all with different skill sets.

It won’t be achieved by playing tennis, squash and ping pong as they are all basically the same movement pattern and call on the same skill sets.  According to the AAOS, there is mounting evidence that children are suffering more and more long term injuries to both muscles and joints and this corresponds to a rise in single sport specialisation at an early age.

Kids bodies are designed to be explored in. They are designed for play. That exploration and play forces children to adapt constantly through a variety of planes and a range of muscle groups in a wide variety of movement patterns.

Stacking repetitive movement patterns in high volume on top of children during their growth phases can leave a child with permanent damage.  It is not just young bodies … but young brains want to explore and children do not have the ability to self actualise in a sport until adolescence.

Their natural curiosity leads them to want to learn something until they think it’s been accomplished (even if the coach thinks it’s only 65% completed). Having a child work against that natural curiosity and focus on the same movement pattern over and over again is a sure fire way to lead them to boredom, mental fatigue, disinterest in the sport or burn out way too soon.

This is different from teaching a child to stick at a task and be resilient. Let’s not get the two confused.  Focusing on a single sport can lead to this.
Although I might put a disclaimer … that focusing on the action to be a fast bowler is far different to learning and focusing on 6 different apparatus and hundreds of skills in a sport like gymnastics.