Safe for a person who takes haldol (haloperidol) + anticholinergic / antihistamine do physical activity at the gym?

Yes: The short answer is yes. I might add, that taking alot of anticholinergic medication, i.e. Cogentin/benztropine or artane/trihexylphenadil-can decrease one's ability to perspire, or sweat. As sweating is the body's natural mechanism to cool off, a concern might be that a person could become overheated. Be sure and drink lots of water and be careful not to become overheated. See: hyperpyrexia.