Usually any weight used on a movie set are fake. Can not shoot take after take of a scene (maybe 10 or more) with real weights. Arnold, for example, would be lying on the floor near death. Can tell when he racks the bar, after squats, just by the sound of the wooden plates hitting the stand. In any case even those plywood/cardboard plates can add up to a somewhat heavy weight for the average guy.
Jeff Bridges is on of the best actors of his generation. Too bad Arnold did not learn much from him.