This 'strand' of activity (which we also refer to when we use the term 'gesture' or 'gesticulation') has certain characteristics which distinguish it from other kinds of activity (such as practical actions, postural adjustments, orientation changes, self-manipulations, and so forth). These include:

• Gestures are 'excursions': phrases of action recognized as 'gesture' move away from a 'rest position' and always return to a rest position (cf. Schegloff 1984).
• 'Peak' structure: Such excursions always have a 'centre' (recognized by naive subjects as the 'business' of the movement, what the movement actually 'does' or what it was 'meant for'). This (since Kendon 1980) has been referred to by some as the 'stroke' of the gesture phrase.
• Well boundedness: phrases of action identified as gesture tend to have clear onsets and offsets. This is in contrast to orientational changes or posture shifts which sometimes can be quite gradual and have no 'peak' structure.
• Symmetry. If you run a film of someone gesturing backwards it is remarkable how difficult it seems to be to see the difference from when you run the film forwards. This suggests that gesture phrases have a symmetry of organization that practical actions, posture shifts (and of course spatial movements, etc.) do not have.