Toastmasters International has a five-minute YouTube video on Gestures and Body Language which warns:
“Gestures that are not coordinated with the speaker’s message will sap the speaker’s energy and shift the audience’s focus away from the intended message.”
I just saw a good example of this in an otherwise excellent recent three-minute YouTube video by Brian Tracy on How to Overcome Your Fear of Public Speaking. Watch his hands starting at 0:38 when he says:
“Most of all, your ability to give effective presentations both to small and large groups will increase your own feeling of self-esteem, self-respect and personal pride.”
As shown above, his gestures for small and large are backward from what would be expected. Perhaps he accidentally switched his word order, but kept the same gesture order.
Larger arm signals can provide a rich nonverbal vocabulary, as is seen in Army Field Manual 21-60 on Visual Signals.