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While we usually don't use fanciness like 3-d motion capture, many kinds of manual therapists utilize movement and postural assessments. Clients often inquire as to why we do this. To view the body's state both in effort against gravity (standing) and out of effort (laying on the table during the session) can reveal quite a bit about the body awareness, attitudinal state and rest/work functioning of the client. Additionally, to have them move or perform an activity will almost always demonstrate training patterns, pain sites, habits and functional/mechanical choices being made (consciously or unconsciously).
Since it can be weird to have someone there watching you stand or move, many practitioners work in small periods of assessment during casual moments or set aside a regular time for that component somewhere in a treatment or series.
Lots of apps and other tools now exist that make relaying the information we see and note to our clients. There are a few for iPads which allow the user to instantly drop lines, put in side by side comparisons, take short videos, etc.
It's important the client trust the process and be given assistance to observe their own improvement, since progress can sometimes feel slow.