During the ALJ hearing, is it okay to have your client physically demonstrate simple movements to show physical limitations that records may not document?

Not really.  There are many reasons for this.  Firstly, hearings are tape recorded and physical movements won’t show up on audio.  As well, any physical limitations that are the basis of a disability claim must have medical records to back it up, not just an ALJ’s observations. Courts have discounted “sit and squirm” opinions from ALJs who “eyeball” the client, and say they have no back problems, for example, because they sit in a hearing for two hours in no obvious discomfort.  DDS is supposed to consider the claimant’s capacity to perform work activities on a sustained basis, not just on what they can or cannot do on a one-time basis.  (See Social Security Rulings 96-8p and 96-9p) https://www.ssa.gov/OP_Home/rulings/rulfind1.html#YRT1996)