Balance (or more correctly vestibular balance) is what helps us all to control our body. The most advanced form of balance is to be still! Children often send us behavioural messages by wriggling, spinning and even hanging upside down.
So when children do things like this, what they are really telling us is - 'If you don't move me, I am going to move myself and I know what I need!' So next time, instead of growling, think about going to the park for a swing, or rolling down a nearby hill, or lying on the office chair and spinning slowly round and round. You may just find, the wriggling and the concentration improves.
Adapted from Moving Smart see here for more on getting babies spinning