This is a very simple (but fun) activity, and although it is not particularly physical, it encourages the children to work together to solve the problem that they have been set.
1) Arrange the children into groups (an even number of children - between 8 and 12 - in each group)
2) Tell the children to stand in a tight circle (facing inwards). Everyone should put their left hand in the circle, and hold someone else's left hand.
3) Now everyone, should put in their right hand, and hold someone else's right hand.
4) WITHOUT letting go of each other's hands, the children should untangle themselves! It is possible, if they work as a team.