If you've ever watched an amateur theatrical performance, you know that nervous people give themselves away with their awkward movements. It's obvious that they have been told to take two steps to the left on a certain line, and then sit on a specific chair. You get so caught up in watching the clumsiness of the actor that you cannot concentrate on the lines of dialogue.
Needless to say, you don't want your audience to be concentrating on your movements and not your words. That's why some speakers choose to stand in one spot; they're afraid they'll be clumsy or fall down or somehow detract from their message. However, standing in one spot throughout a presentation can be just as much of a distraction, especially if the speaker is so still and statue-like that you're just waiting for a pigeon to come roost on his shoulder.
There are a number of reasons why you should move during your presentations:
To get closer and build a physical connection with the audience.
To create a stronger sense of emotion.
To change the visual pattern.
To make a physical transition.
To change the rhythm of the speech. (If you have a frenetic type of delivery and move constantly, then when you stop it will be twice as effective.)
To make a point more intense or emphatic.
To create greater audience attention.
To create a flow.
Use lateral movements whenever possible (moving from side to side rather than from front to back). They're not only easier for the audience to see, they create more visual interest. When you do move, move purposely—don't inch or sidle.
When we're in conversation with one another, we're always moving. We shift in our seats, or move a few feet to the left or right, or turn our heads to look in a different direction. It's natural. Your movements on stage should be natural as well—and that comes with practice. When you're rehearsing your presentation, practice your movements, gestures, and mannerisms as well.