A few years ago I was doing seated lat pulldowns. The gym instructor came by and suggested an additional exercise. Using the same machine I stood up and started with my upper arms by my sides and my forearms parallel to the floor. I then pulled down, using forearms only, and back to start. I then did the reps that fitted with the rest of my routine. It seems like a good exercise but: a) Do you know what it is called please? b) Can you please tell me which muscles it works?