I don't usually post just lurk but here goes. I shoot only long bows. I have to lock the bow arm on target literally hold it perfectly still, then I will pull straight thru the shot. I guess it is the push pull effect. When I say lock my arm I mean rigid with out my elbow being bent inwards. As others have said back tension will take over if the draw is complete, If my form is sloppy weak bow arm then I will pluck, drop my arm, creep, and generally blow the shot. This tends to happen when I don't concentrate on that bow arm. Just my two cents worth on a very good topic.