Keeping your group alert and engaged can be a struggle sometimes...especially after lunch breaks or heavy sessions based on theory.
At times, it may be necessary to get the audience to refocus or even move onto a new subject i.e. park the topic they've just went through.
A good facilitator should be able to feel the energy levels and keep the audience positively engaged.
A good support is a bank of energizer activities to recharge and refocus the group.