Dead arms

Had a different Pump class instructor this morning - the usual one is on holidays. And my arms are dead. I have always thought the usual instructor was a bit wimpy with her workouts and this has confirmed it. I feel like I'm not getting my money's worth normally now. I'm thinking about emailing the gym. It isn't like I have a choice of instructors, Monday morning is the only pump class on the days I go (and the only other option is Thursday morning, when I have Bible study).