What can be a common unexpected emotion when catching a ball?

Fear

Explanation:

A common, unexpected emotion when catching a ball could be that of fear. It is unexpected to feel fear when catching a ball, because we rationally know that there is nothing we have to worry about. A ball is unlikely to cause serious harm. Nevertheless, it is likely that we feel fearful of a ball because of the element of surprise. Thus, this also makes fear a common reaction.

c- dynamic stretching