Hi Jon,

Our clinical advisor said the following:

I think it is certainly fine to do material handling testing in sitting-the only question would  be why?  If it directly relates to a job demand, it is preferred vs. optional.  I do not know of any research related to material handling in sitting, however.
 
RMA recommends against static isometric lift testing-particularly if it does not relate to a specific job demand.  I would use considerable caution even when such testing is relevant to a job demand-as static forces on the lumbar spine suggest a high probability of injury in that area.  Very few jobs I have encountered require static lifting-especially with legs straight and bending at the waist.

We hope this helps.

Thanks

Jenn