HIs arm is locked because his draw length is TOO LONG. No doubt about it. Your shooting would improve tremdously if it were about an inch shorter it looks. Start with 1/2 inch and go from there. It'll feel odd for about a day if you do it in 1/2 increments. Arm locked, leaning back... TOO TOO LONG. Too much palm in the bow yada yada yada. My pro shop would fix you up in about one visit. Get the tip of that finger off the trigger. All the above make it impossible to use back tension and get a really crisp surprise shot off. You trigger it everytime. Then some day you'll start punching the shot. Then some day you'll get target panic and start shooting on the move. Ohhhhhhhhhhhh the misery of it all.[&:]