From Ergo Log
The preacher curl, or the Scott curl, is not such a good exercise for the biceps as many bodybuilders think. According to sports scientists at the Federal University of Rio de Janeiro in Brazil, you are better off doing the incline curl or the classic standing curl.
The Brazilians got 22 male subjects, all of whom had been doing weight training for at least a year, to perform three different types of curl exercise. The versions they did are shown below. The researchers attached electrodes to the men’s biceps so they could measure how hard the muscles had to work.
Dumbbell Biceps Curl
Incline Dumbbell Curl
Dumbbell Preacher Curl
The figures below show that there is not much difference in effectiveness between the incline curl and the standard curl, but that in comparison with these the preacher curl loses out in the third concentric phase and the first eccentric phase of the movement.
In addition, the preacher curl involves a shorter movement than the other versions.
“For the Dumbbell Preacher Curl cycle, the activation of biceps brachii long head was maximal only for elbow joint angles close to full extension, and the elbow joint range of motion was shorter”, the Brazilians summarise. “The Incline Dumbbell Curl and the Dumbbell Biceps Curl resulted in a considerable neuromuscular effort throughout the whole elbow range of motion and, thus, may be preferable for the improvement of biceps brachii force in training programs.”
J Sports Sci Med. 2009 Mar 1;8(1):24-9.