I'll tell you about my experiences with both and maybe that'll help? Right now I'm doing in-patient hours at a military hospital in what I would call "acute care". These folks are usually in Med-Surg wards, though sometimes we visit the ICU or psych ward. Many are coming out of orthopedic surgeries (but we also have cardiac, oncology, and lots of other types of patients) and have been in hospital for less than a week. The PT's job is to prevent as much as possible loss of strength and function while the patient is bed-ridden (doing bed exercises), and to get them up and moving as much as possible once they can (walking around the floor, practicing walking up and down stairs, using walker/crutches, getting into/out of car) to ensure basic safety when they are discharged. Mostly we walk slowly around the nurses station. We don't usually spend more than 20 minutes or so with a patient, once or twice a day. Discharge is usually imminent - within a few days, whereas in the rehab unit we would speak of discharge in terms of weeks or months.
My first volunteer position was at a children's hospital in the rehab unit. This unit is what I would call sub-acute care (hopefully I'm right!). These kids were medically stable but still under "observation" and stayed sometimes months at a time receiving medical and therapy services - OT, PT, and speech. They usually came after having surgeries or other medical care, head/neuro trauma, etc, having already spent some time in the "acute care" setting. Patients were seen about 2 hours per day for each type of therapy, so six hours of therapy per day, sometimes more if needed. The purpose of therapy was pretty broad and much more in-depth than in acute care. The therapists would often work together, across disciplines, and with coordinated goals.
I'm not sure if my categorization is entirely accurate or universally acceptable. Hopefully someone else can chime in to confirm/deny!
